Right now the kernel on x86-64 has a 100% lazy fpu behavior: after *every*
context switch a trap is taken for the first FPU use to restore the FPU
context lazily. This is of course great for applications that have very
sporadic or no FPU use (since then you avoid doing the expensive
save/restore all the time). However for very frequent FPU users... you
take an extra trap every context switch.
The patch below adds a simple heuristic to this code: After 5 consecutive
context switches of FPU use, the lazy behavior is disabled and the context
gets restored every context switch. If the app indeed uses the FPU, the
trap is avoided. (the chance of the 6th time slice using FPU after the
previous 5 having done so are quite high obviously).
After 256 switches, this is reset and lazy behavior is returned (until
there are 5 consecutive ones again). The reason for this is to give apps
that do longer bursts of FPU use still the lazy behavior back after some
time.
[akpm@osdl.org: place new task_struct field next to jit_keyring to save space]
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Cleanup allocation and freeing of tsk->delays used by delay accounting.
This solves two problems reported for delay accounting:
1. oops in __delayacct_blkio_ticks
http://www.uwsg.indiana.edu/hypermail/linux/kernel/0608.2/1844.html
Currently tsk->delays is getting freed too early in task exit which can
cause a NULL tsk->delays to get accessed via reading of /proc/<tgid>/stats.
The patch fixes this problem by freeing tsk->delays closer to when
task_struct itself is freed up. As a result, it also eliminates the use of
tsk->delays_lock which was only being used (inadequately) to safeguard
access to tsk->delays while a task was exiting.
2. Possible memory leak in kernel/delayacct.c
http://www.uwsg.indiana.edu/hypermail/linux/kernel/0608.2/1389.html
The patch cleans up tsk->delays allocations after a bad fork which was
missing earlier.
The patch has been tested to fix the problems listed above and stress
tested with rapid calls to delay accounting's taskstats command interface
(which is the other path that can access the same data, besides the /proc
interface causing the oops above).
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
It should be possible to suspend, either to RAM or to disk, if there's a
traced process that has just reached a breakpoint. However, this is a
special case, because its parent process might have been frozen already and
then we are unable to deliver the "freeze" signal to the traced process.
If this happens, it's better to cancel the freezing of the traced process.
Ref. http://bugzilla.kernel.org/show_bug.cgi?id=6787
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Send per-tgid data only once during exit of a thread group instead of once
with each member thread exit.
Currently, when a thread exits, besides its per-tid data, the per-tgid data
of its thread group is also sent out, if its thread group is non-empty.
The per-tgid data sent consists of the sum of per-tid stats for all
*remaining* threads of the thread group.
This patch modifies this sending in two ways:
- the per-tgid data is sent only when the last thread of a thread group
exits. This cuts down heavily on the overhead of sending/receiving
per-tgid data, especially when other exploiters of the taskstats
interface aren't interested in per-tgid stats
- the semantics of the per-tgid data sent are changed. Instead of being
the sum of per-tid data for remaining threads, the value now sent is the
true total accumalated statistics for all threads that are/were part of
the thread group.
The patch also addresses a minor issue where failure of one accounting
subsystem to fill in the taskstats structure was causing the send of
taskstats to not be sent at all.
The patch has been tested for stability and run cerberus for over 4 hours
on an SMP.
[akpm@osdl.org: bugfixes]
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Make the task-related schedstats functions callable by delay accounting even
if schedstats collection isn't turned on. This removes the dependency of
delay accounting on schedstats.
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Erich Focht <efocht@ess.nec.de>
Cc: Levent Serinol <lserinol@gmail.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Unlike earlier iterations of the delay accounting patches, now delays are only
collected for the actual I/O waits rather than try and cover the delays seen
in I/O submission paths.
Account separately for block I/O delays incurred as a result of swapin page
faults whose frequency can be affected by the task/process' rss limit. Hence
swapin delays can act as feedback for rss limit changes independent of I/O
priority changes.
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Erich Focht <efocht@ess.nec.de>
Cc: Levent Serinol <lserinol@gmail.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initialization code related to collection of per-task "delay" statistics which
measure how long it had to wait for cpu, sync block io, swapping etc. The
collection of statistics and the interface are in other patches. This patch
sets up the data structures and allows the statistics collection to be
disabled through a kernel boot parameter.
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Erich Focht <efocht@ess.nec.de>
Cc: Levent Serinol <lserinol@gmail.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
convert:
- runqueue_t to 'struct rq'
- prio_array_t to 'struct prio_array'
- migration_req_t to 'struct migration_req'
I was the one who added these but they are both against the kernel coding
style and also were used inconsistently at places. So just get rid of them at
once, now that we are flushing the scheduler patch-queue anyway.
Conversion was mostly scripted, the result was reviewed and all secondary
whitespace and style impact (if any) was fixed up by hand.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
cleanup: remove task_t and convert all the uses to struct task_struct. I
introduced it for the scheduler anno and it was a mistake.
Conversion was mostly scripted, the result was reviewed and all
secondary whitespace and style impact (if any) was fixed up by hand.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Do 'make oldconfig' and accept all the defaults for new config options -
reboot into the kernel and if everything goes well it should boot up fine and
you should have /proc/lockdep and /proc/lockdep_stats files.
Typically if the lock validator finds some problem it will print out
voluminous debug output that begins with "BUG: ..." and which syslog output
can be used by kernel developers to figure out the precise locking scenario.
What does the lock validator do? It "observes" and maps all locking rules as
they occur dynamically (as triggered by the kernel's natural use of spinlocks,
rwlocks, mutexes and rwsems). Whenever the lock validator subsystem detects a
new locking scenario, it validates this new rule against the existing set of
rules. If this new rule is consistent with the existing set of rules then the
new rule is added transparently and the kernel continues as normal. If the
new rule could create a deadlock scenario then this condition is printed out.
When determining validity of locking, all possible "deadlock scenarios" are
considered: assuming arbitrary number of CPUs, arbitrary irq context and task
context constellations, running arbitrary combinations of all the existing
locking scenarios. In a typical system this means millions of separate
scenarios. This is why we call it a "locking correctness" validator - for all
rules that are observed the lock validator proves it with mathematical
certainty that a deadlock could not occur (assuming that the lock validator
implementation itself is correct and its internal data structures are not
corrupted by some other kernel subsystem). [see more details and conditionals
of this statement in include/linux/lockdep.h and
Documentation/lockdep-design.txt]
Furthermore, this "all possible scenarios" property of the validator also
enables the finding of complex, highly unlikely multi-CPU multi-context races
via single single-context rules, increasing the likelyhood of finding bugs
drastically. In practical terms: the lock validator already found a bug in
the upstream kernel that could only occur on systems with 3 or more CPUs, and
which needed 3 very unlikely code sequences to occur at once on the 3 CPUs.
That bug was found and reported on a single-CPU system (!). So in essence a
race will be found "piecemail-wise", triggering all the necessary components
for the race, without having to reproduce the race scenario itself! In its
short existence the lock validator found and reported many bugs before they
actually caused a real deadlock.
To further increase the efficiency of the validator, the mapping is not per
"lock instance", but per "lock-class". For example, all struct inode objects
in the kernel have inode->inotify_mutex. If there are 10,000 inodes cached,
then there are 10,000 lock objects. But ->inotify_mutex is a single "lock
type", and all locking activities that occur against ->inotify_mutex are
"unified" into this single lock-class. The advantage of the lock-class
approach is that all historical ->inotify_mutex uses are mapped into a single
(and as narrow as possible) set of locking rules - regardless of how many
different tasks or inode structures it took to build this set of rules. The
set of rules persist during the lifetime of the kernel.
To see the rough magnitude of checking that the lock validator does, here's a
portion of /proc/lockdep_stats, fresh after bootup:
lock-classes: 694 [max: 2048]
direct dependencies: 1598 [max: 8192]
indirect dependencies: 17896
all direct dependencies: 16206
dependency chains: 1910 [max: 8192]
in-hardirq chains: 17
in-softirq chains: 105
in-process chains: 1065
stack-trace entries: 38761 [max: 131072]
combined max dependencies: 2033928
hardirq-safe locks: 24
hardirq-unsafe locks: 176
softirq-safe locks: 53
softirq-unsafe locks: 137
irq-safe locks: 59
irq-unsafe locks: 176
The lock validator has observed 1598 actual single-thread locking patterns,
and has validated all possible 2033928 distinct locking scenarios.
More details about the design of the lock validator can be found in
Documentation/lockdep-design.txt, which can also found at:
http://redhat.com/~mingo/lockdep-patches/lockdep-design.txt
[bunk@stusta.de: cleanups]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Accurate hard-IRQ-flags and softirq-flags state tracing.
This allows us to attach extra functionality to IRQ flags on/off
events (such as trace-on/off).
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Generic lock debugging:
- generalized lock debugging framework. For example, a bug in one lock
subsystem turns off debugging in all lock subsystems.
- got rid of the caller address passing (__IP__/__IP_DECL__/etc.) from
the mutex/rtmutex debugging code: it caused way too much prototype
hackery, and lockdep will give the same information anyway.
- ability to do silent tests
- check lock freeing in vfree too.
- more finegrained debugging options, to allow distributions to
turn off more expensive debugging features.
There's no separate 'held mutexes' list anymore - but there's a 'held locks'
stack within lockdep, which unifies deadlock detection across all lock
classes. (this is independent of the lockdep validation stuff - lockdep first
checks whether we are holding a lock already)
Here are the current debugging options:
CONFIG_DEBUG_MUTEXES=y
CONFIG_DEBUG_LOCK_ALLOC=y
which do:
config DEBUG_MUTEXES
bool "Mutex debugging, basic checks"
config DEBUG_LOCK_ALLOC
bool "Detect incorrect freeing of live mutexes"
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch adds a call to the extended security_task_kill hook introduced by
the prior patch to the kill_proc_info_as_uid function so that these signals
can be properly mediated by security modules. It also updates the existing
hook call in check_kill_permission.
Signed-off-by: David Quigley <dpquigl@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
When the priority of a task, which is blocked on a lock, changes we must
propagate this change into the PI lock chain. Therefor the chain walk code
is changed to get rid of the references to current to avoid false positives
in the deadlock detector, as setscheduler might be called by a task which
holds the lock on which the task whose priority is changed is blocked.
Also add some comments about the get/put_task_struct usage to avoid
confusion.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This adds the actual pi-futex implementation, based on rt-mutexes.
[dino@in.ibm.com: fix an oops-causing race]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Dinakar Guniguntala <dino@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
RT-mutex tester: scriptable tester for rt mutexes, which allows userspace
scripting of mutex unit-tests (and dynamic tests as well), using the actual
rt-mutex implementation of the kernel.
[akpm@osdl.org: fixlet]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Core functions for the rt-mutex subsystem.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add framework to boost/unboost the priority of RT tasks.
This consists of:
- caching the 'normal' priority in ->normal_prio
- providing a functions to set/get the priority of the task
- make sched_setscheduler() aware of boosting
The effective_prio() cleanups also fix a priority-calculation bug pointed out
by Andrey Gelman, in set_user_nice().
has_rt_policy() fix: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Andrey Gelman <agelman@012.net.il>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
sysfs entries 'sched_mc_power_savings' and 'sched_smt_power_savings' in
/sys/devices/system/cpu/ control the MC/SMT power savings policy for the
scheduler.
Based on the values (1-enable, 0-disable) for these controls, sched groups
cpu power will be determined for different domains. When power savings
policy is enabled and under light load conditions, scheduler will minimize
the physical packages/cpu cores carrying the load and thus conserving
power(with a perf impact based on the workload characteristics... see OLS
2005 CMP kernel scheduler paper for more details..)
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Con Kolivas <kernel@kolivas.org>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Try to handle mem allocation failures in build_sched_domains by bailing out
and cleaning up thus-far allocated memory. The patch has a direct consequence
that we disable load balancing completely (even at sibling level) upon *any*
memory allocation failure.
[Lee.Schermerhorn@hp.com: bugfix]
Signed-off-by: Srivatsa Vaddagir <vatsa@in.ibm.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Problem:
The introduction of separate run queues per CPU has brought with it "nice"
enforcement problems that are best described by a simple example.
For the sake of argument suppose that on a single CPU machine with a
nice==19 hard spinner and a nice==0 hard spinner running that the nice==0
task gets 95% of the CPU and the nice==19 task gets 5% of the CPU. Now
suppose that there is a system with 2 CPUs and 2 nice==19 hard spinners and
2 nice==0 hard spinners running. The user of this system would be entitled
to expect that the nice==0 tasks each get 95% of a CPU and the nice==19
tasks only get 5% each. However, whether this expectation is met is pretty
much down to luck as there are four equally likely distributions of the
tasks to the CPUs that the load balancing code will consider to be balanced
with loads of 2.0 for each CPU. Two of these distributions involve one
nice==0 and one nice==19 task per CPU and in these circumstances the users
expectations will be met. The other two distributions both involve both
nice==0 tasks being on one CPU and both nice==19 being on the other CPU and
each task will get 50% of a CPU and the user's expectations will not be
met.
Solution:
The solution to this problem that is implemented in the attached patch is
to use weighted loads when determining if the system is balanced and, when
an imbalance is detected, to move an amount of weighted load between run
queues (as opposed to a number of tasks) to restore the balance. Once
again, the easiest way to explain why both of these measures are necessary
is to use a simple example. Suppose that (in a slight variation of the
above example) that we have a two CPU system with 4 nice==0 and 4 nice=19
hard spinning tasks running and that the 4 nice==0 tasks are on one CPU and
the 4 nice==19 tasks are on the other CPU. The weighted loads for the two
CPUs would be 4.0 and 0.2 respectively and the load balancing code would
move 2 tasks resulting in one CPU with a load of 2.0 and the other with
load of 2.2. If this was considered to be a big enough imbalance to
justify moving a task and that task was moved using the current
move_tasks() then it would move the highest priority task that it found and
this would result in one CPU with a load of 3.0 and the other with a load
of 1.2 which would result in the movement of a task in the opposite
direction and so on -- infinite loop. If, on the other hand, an amount of
load to be moved is calculated from the imbalance (in this case 0.1) and
move_tasks() skips tasks until it find ones whose contributions to the
weighted load are less than this amount it would move two of the nice==19
tasks resulting in a system with 2 nice==0 and 2 nice=19 on each CPU with
loads of 2.1 for each CPU.
One of the advantages of this mechanism is that on a system where all tasks
have nice==0 the load balancing calculations would be mathematically
identical to the current load balancing code.
Notes:
struct task_struct:
has a new field load_weight which (in a trade off of space for speed)
stores the contribution that this task makes to a CPU's weighted load when
it is runnable.
struct runqueue:
has a new field raw_weighted_load which is the sum of the load_weight
values for the currently runnable tasks on this run queue. This field
always needs to be updated when nr_running is updated so two new inline
functions inc_nr_running() and dec_nr_running() have been created to make
sure that this happens. This also offers a convenient way to optimize away
this part of the smpnice mechanism when CONFIG_SMP is not defined.
int try_to_wake_up():
in this function the value SCHED_LOAD_BALANCE is used to represent the load
contribution of a single task in various calculations in the code that
decides which CPU to put the waking task on. While this would be a valid
on a system where the nice values for the runnable tasks were distributed
evenly around zero it will lead to anomalous load balancing if the
distribution is skewed in either direction. To overcome this problem
SCHED_LOAD_SCALE has been replaced by the load_weight for the relevant task
or by the average load_weight per task for the queue in question (as
appropriate).
int move_tasks():
The modifications to this function were complicated by the fact that
active_load_balance() uses it to move exactly one task without checking
whether an imbalance actually exists. This precluded the simple
overloading of max_nr_move with max_load_move and necessitated the addition
of the latter as an extra argument to the function. The internal
implementation is then modified to move up to max_nr_move tasks and
max_load_move of weighted load. This slightly complicates the code where
move_tasks() is called and if ever active_load_balance() is changed to not
use move_tasks() the implementation of move_tasks() should be simplified
accordingly.
struct sched_group *find_busiest_group():
Similar to try_to_wake_up(), there are places in this function where
SCHED_LOAD_SCALE is used to represent the load contribution of a single
task and the same issues are created. A similar solution is adopted except
that it is now the average per task contribution to a group's load (as
opposed to a run queue) that is required. As this value is not directly
available from the group it is calculated on the fly as the queues in the
groups are visited when determining the busiest group.
A key change to this function is that it is no longer to scale down
*imbalance on exit as move_tasks() uses the load in its scaled form.
void set_user_nice():
has been modified to update the task's load_weight field when it's nice
value and also to ensure that its run queue's raw_weighted_load field is
updated if it was runnable.
From: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
With smpnice, sched groups with highest priority tasks can mask the imbalance
between the other sched groups with in the same domain. This patch fixes some
of the listed down scenarios by not considering the sched groups which are
lightly loaded.
a) on a simple 4-way MP system, if we have one high priority and 4 normal
priority tasks, with smpnice we would like to see the high priority task
scheduled on one cpu, two other cpus getting one normal task each and the
fourth cpu getting the remaining two normal tasks. but with current
smpnice extra normal priority task keeps jumping from one cpu to another
cpu having the normal priority task. This is because of the
busiest_has_loaded_cpus, nr_loaded_cpus logic.. We are not including the
cpu with high priority task in max_load calculations but including that in
total and avg_load calcuations.. leading to max_load < avg_load and load
balance between cpus running normal priority tasks(2 Vs 1) will always show
imbalanace as one normal priority and the extra normal priority task will
keep moving from one cpu to another cpu having normal priority task..
b) 4-way system with HT (8 logical processors). Package-P0 T0 has a
highest priority task, T1 is idle. Package-P1 Both T0 and T1 have 1 normal
priority task each.. P2 and P3 are idle. With this patch, one of the
normal priority tasks on P1 will be moved to P2 or P3..
c) With the current weighted smp nice calculations, it doesn't always make
sense to look at the highest weighted runqueue in the busy group..
Consider a load balance scenario on a DP with HT system, with Package-0
containing one high priority and one low priority, Package-1 containing one
low priority(with other thread being idle).. Package-1 thinks that it need
to take the low priority thread from Package-0. And find_busiest_queue()
returns the cpu thread with highest priority task.. And ultimately(with
help of active load balance) we move high priority task to Package-1. And
same continues with Package-0 now, moving high priority task from package-1
to package-0.. Even without the presence of active load balance, load
balance will fail to balance the above scenario.. Fix find_busiest_queue
to use "imbalance" when it is lightly loaded.
[kernel@kolivas.org: sched: store weighted load on up]
[kernel@kolivas.org: sched: add discrete weighted cpu load function]
[suresh.b.siddha@intel.com: sched: remove dead code]
Signed-off-by: Peter Williams <pwil3058@bigpond.com.au>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Cc: John Hawkes <hawkes@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
To keep the dcache from filling up with dead /proc entries we flush them on
process exit. However over the years that code has gotten hairy with a
dentry_pointer and a lock in task_struct and misdocumented as a correctness
feature.
I have rewritten this code to look and see if we have a corresponding entry in
the dcache and if so flush it on process exit. This removes the extra fields
in the task_struct and allows me to trivially handle the case of a
/proc/<tgid>/task/<pid> entry as well as the current /proc/<pid> entries.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In current 2.6.17 implementation, signal_struct refered from task_struct is
used for per-process data structure. The pacct facility also uses it as a
per-process data structure to store stime, utime, minflt, majflt. But those
members are saved in __exit_signal(). It's too late.
For example, if some threads exits at same time, pacct facility has a
possibility to drop accountings for a part of those threads. (see, the
following 'The results of original 2.6.17 kernel') I think accounting
information should be completely collected into the per-process data structure
before writing out an accounting record.
This patch fixes this matter. Accumulation of stime, utime, minflt and majflt
are done before generating accounting record.
[mingo@elte.hu: fix acct_collect() siglock bug found by lockdep]
Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
When pacct facility generate an 'ac_flag' field in accounting record, it
refers a task_struct of the thread which died last in the process. But any
other task_structs are ignored.
Therefore, pacct facility drops ASU flag even if root-privilege operations are
used by any other threads except the last one. In addition, AFORK flag is
always set when the thread of group-leader didn't die last, although this
process has called execve() after fork().
We have a same matter in ac_exitcode. The recorded ac_exitcode is an exit
code of the last thread in the process. There is a possibility this exitcode
is not the group leader's one.
The pacct facility need an i/o operation when an accounting record is
generated. There is a possibility to wake OOM killer up. If OOM killer is
activated, it kills some processes to make them release process memory
regions.
But acct_process() is called in the killed processes context before calling
exit_mm(), so those processes cannot release own memory. In the results, any
processes stop in this point and it finally cause a system stall.
A process flag to indicate whether we are doing sync io is incredibly
ugly. It also causes performance problems when one does a lot of async
io and then proceeds to sync it. Part of the io will go out as async,
and the other part as sync. This causes a disconnect between the
previously submitted io and the synced io. For io schedulers such as CFQ,
this will cause us lost merges and suboptimal behaviour in scheduling.
Remove PF_SYNCWRITE completely from the fsync/msync paths, and let
the O_DIRECT path just directly indicate that the writes are sync
by using WRITE_SYNC instead.
Signed-off-by: Jens Axboe <axboe@suse.de>
After a lot of reading the code and thinking about how it behaves I have
managed to figure out what the current ptrace locking rules are. The
current code is in much better that it appears at first glance. The
troublesome code paths are actually the code paths that violate the current
rules.
ptrace uses simple exclusive access as it's locking. You can only touch
task->ptrace if the task is stopped and you are the ptracer, or if the task
is running and are the task itself.
Very simple, very easy to maintain. It just needs to be documented so
people know not to touch ptrace from elsewhere.
Currently we do have a few pieces of code that are in violation of this
rule. Particularly the core dump code, and ptrace_attach. But so far the
code looks fixable.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The following series of patches introduces a kernel API for inotify,
making it possible for kernel modules to benefit from inotify's
mechanism for watching inodes. With these patches, inotify will
maintain for each caller a list of watches (via an embedded struct
inotify_watch), where each inotify_watch is associated with a
corresponding struct inode. The caller registers an event handler and
specifies for which filesystem events their event handler should be
called per inotify_watch.
Signed-off-by: Amy Griffis <amy.griffis@hp.com>
Acked-by: Robert Love <rml@novell.com>
Acked-by: John McCutchan <john@johnmccutchan.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
There was a whole load of crap exposed which should have been inside the
existing #ifdef __KERNEL__ part. Also hide struct sched_param for now,
since glibc has its own and doesn't like being given ours (yet).
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
For now, just make sure all inclusion of private header files is done
within #ifdef __KERNEL__. There'll be more to clean up later.
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
While we can currently walk through thread groups, process groups, and
sessions with just the rcu_read_lock, this opens the door to walking the
entire task list.
We already have all of the other RCU guarantees so there is no cost in
doing this, this should be enough so that proc can stop taking the
tasklist lock during readdir.
prev_task was killed because it has no users, and using it will miss new
tasks when doing an rcu traversal.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Somehow in the midst of dotting i's and crossing t's during
the merge up to rc1 we wound up keeping __put_task_struct_cb
when it should have been killed as it no longer has any users.
Sorry I probably should have caught this while it was
still in the -mm tree.
Having the old code there gets confusing when reading
through the code and trying to understand what is
happening.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* 'splice' of git://brick.kernel.dk/data/git/linux-2.6-block:
[PATCH] vfs: add splice_write and splice_read to documentation
[PATCH] Remove sys_ prefix of new syscalls from __NR_sys_*
[PATCH] splice: warning fix
[PATCH] another round of fs/pipe.c cleanups
[PATCH] splice: comment styles
[PATCH] splice: add Ingo as addition copyright holder
[PATCH] splice: unlikely() optimizations
[PATCH] splice: speedups and optimizations
[PATCH] pipe.c/fifo.c code cleanups
[PATCH] get rid of the PIPE_*() macros
[PATCH] splice: speedup __generic_file_splice_read
[PATCH] splice: add direct fd <-> fd splicing support
[PATCH] splice: add optional input and output offsets
[PATCH] introduce a "kernel-internal pipe object" abstraction
[PATCH] splice: be smarter about calling do_page_cache_readahead()
[PATCH] splice: optimize the splice buffer mapping
[PATCH] splice: cleanup __generic_file_splice_read()
[PATCH] splice: only call wake_up_interruptible() when we really have to
[PATCH] splice: potential !page dereference
[PATCH] splice: mark the io page as accessed
Before commit 47e65328a7, next_thread() took
a const task_t. Reinstate the const qualifier, getting the next thread
never changes the current thread.
Signed-off-by: Keith Owens <kaos@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
It's more efficient for sendfile() emulation. Basically we cache an
internal private pipe and just use that as the intermediate area for
pages. Direct splicing is not available from sys_splice(), it is only
meant to be used for sendfile() emulation.
Additional patch from Ingo Molnar to avoid the PIPE_BUFFERS loop at
exit for the normal fast path.
Signed-off-by: Jens Axboe <axboe@suse.de>
Oleg Nesterov spotted two interesting bugs with the current de_thread
code. The simplest is a long standing double decrement of
__get_cpu_var(process_counts) in __unhash_process. Caused by
two processes exiting when only one was created.
The other is that since we no longer detach from the thread_group list
it is possible for do_each_thread when run under the tasklist_lock to
see the same task_struct twice. Once on the task list as a
thread_group_leader, and once on the thread list of another
thread.
The double appearance in do_each_thread can cause a double increment
of mm_core_waiters in zap_threads resulting in problems later on in
coredump_wait.
To remedy those two problems this patch takes the simple approach
of changing the old thread group leader into a child thread.
The only routine in release_task that cares is __unhash_process,
and it can be trivially seen that we handle cleaning up a
thread group leader properly.
Since de_thread doesn't change the pid of the exiting leader process
and instead shares it with the new leader process. I change
thread_group_leader to recognize group leadership based on the
group_leader field and not based on pids. This should also be
slightly cheaper then the existing thread_group_leader macro.
I performed a quick audit and I couldn't see any user of
thread_group_leader that cared about the difference.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Simplifies the code, reduces the need for 4 pid hash tables, and makes the
code more capable.
In the discussions I had with Oleg it was felt that to a large extent the
cleanup itself justified the work. With struct pid being dynamically
allocated meant we could create the hash table entry when the pid was
allocated and free the hash table entry when the pid was freed. Instead of
playing with the hash lists when ever a process would attach or detach to a
process.
For myself the fact that it gave what my previous task_ref patch gave for free
with simpler code was a big win. The problem is that if you hold a reference
to struct task_struct you lock in 10K of low memory. If you do that in a user
controllable way like /proc does, with an unprivileged but hostile user space
application with typical resource limits of 1000 fds and 100 processes I can
trigger the OOM killer by consuming all of low memory with task structs, on a
machine wight 1GB of low memory.
If I instead hold a reference to struct pid which holds a pointer to my
task_struct, I don't suffer from that problem because struct pid is 2 orders
of magnitude smaller. In fact struct pid is small enough that most other
kernel data structures dwarf it, so simply limiting the number of referring
data structures is enough to prevent exhaustion of low memory.
This splits the current struct pid into two structures, struct pid and struct
pid_link, and reduces our number of hash tables from PIDTYPE_MAX to just one.
struct pid_link is the per process linkage into the hash tables and lives in
struct task_struct. struct pid is given an indepedent lifetime, and holds
pointers to each of the pid types.
The independent life of struct pid simplifies attach_pid, and detach_pid,
because we are always manipulating the list of pids and not the hash table.
In addition in giving struct pid an indpendent life it makes the concept much
more powerful.
Kernel data structures can now embed a struct pid * instead of a pid_t and
not suffer from pid wrap around problems or from keeping unnecessarily
large amounts of memory allocated.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
A big problem with rcu protected data structures that are also reference
counted is that you must jump through several hoops to increase the reference
count. I think someone finally implemented atomic_inc_not_zero(&count) to
automate the common case. Unfortunately this means you must special case the
rcu access case.
When data structures are only visible via rcu in a manner that is not
determined by the reference count on the object (i.e. tasks are visible until
their zombies are reaped) there is a much simpler technique we can employ.
Simply delaying the decrement of the reference count until the rcu interval is
over.
What that means is that the proc code that looks up a task and later
wants to sleep can now do:
rcu_read_lock();
task = find_task_by_pid(some_pid);
if (task) {
get_task_struct(task);
}
rcu_read_unlock();
The effect on the rest of the kernel is that put_task_struct becomes cheaper
and immediate, and in the case where the task has been reaped it frees the
task immediate instead of unnecessarily waiting an until the rcu interval is
over.
Cleanup of task_struct does not happen when its reference count drops to
zero, instead cleanup happens when release_task is called. Tasks can only
be looked up via rcu before release_task is called. All rcu protected
members of task_struct are freed by release_task.
Therefore we can move call_rcu from put_task_struct into release_task. And
we can modify release_task to not immediately release the reference count
but instead have it call put_task_struct from the function it gives to
call_rcu.
The end result:
- get_task_struct is safe in an rcu context where we have just looked
up the task.
- put_task_struct() simplifies into its old pre rcu self.
This reorganization also makes put_task_struct uncallable from modules as
it is not exported but it does not appear to be called from any modules so
this should not be an issue, and is trivially fixed.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This just got nuked in mainline. Bring it back because Eric's patches use it.
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
To increase the strength of SCHED_BATCH as a scheduling hint we can
activate batch tasks on the expired array since by definition they are
latency insensitive tasks.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The activated flag in task_struct is used to track different sleep types and
its usage is somewhat obfuscated. Convert the variable to an enum with more
descriptive names without altering the function.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Currently, count_active_tasks() calls both nr_running() &
nr_interruptible(). Each of these functions does a "for_each_cpu" & reads
values from the runqueue of each cpu. Although this is not a lot of
instructions, each runqueue may be located on different node. Depending on
the architecture, a unique TLB entry may be required to access each
runqueue.
Since there may be more runqueues than cpu TLB entries, a scan of all
runqueues can trash the TLB. Each memory reference incurs a TLB miss &
refill.
In addition, the runqueue cacheline that contains nr_running &
nr_uninterruptible may be evicted from the cache between the two passes.
This causes unnecessary cache misses.
Combining nr_running() & nr_interruptible() into a single function
substantially reduces the TLB & cache misses on large systems. This should
have no measureable effect on smaller systems.
On a 128p IA64 system running a memory stress workload, the new function
reduced the overhead of calc_load() from 605 usec/call to 324 usec/call.
Signed-off-by: Jack Steiner <steiner@sgi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Move 'tsk->sighand = NULL' from cleanup_sighand() to __exit_signal(). This
makes the exit path more understandable and allows us to do
cleanup_sighand() outside of ->siglock protected section.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch kills PIDTYPE_TGID pid_type thus saving one hash table in
kernel/pid.c and speeding up subthreads create/destroy a bit. It is also a
preparation for the further tref/pids rework.
This patch adds 'struct list_head thread_group' to 'struct task_struct'
instead.
We don't detach group leader from PIDTYPE_PID namespace until another
thread inherits it's ->pid == ->tgid, so we are safe wrt premature
free_pidmap(->tgid) call.
Currently there are no users of find_task_by_pid_type(PIDTYPE_TGID).
Should the need arise, we can use find_task_by_pid()->group_leader.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-By: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
__exit_signal() is private to release_task() now. I think it is better to
make it static in kernel/exit.c and export flush_sigqueue() instead - this
function is much more simple and straightforward.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Cosmetic, rename __exit_sighand to cleanup_sighand and move it close to
copy_sighand().
This matches copy_signal/cleanup_signal naming, and I think it is easier to
follow.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
__exit_signal() does important cleanups atomically under ->siglock. It is
also called from copy_process's error path. This is not good, for example we
can't move __unhash_process() under ->siglock for that reason.
We should not mix these 2 paths, just look at ugly 'if (p->sighand)' under
'bad_fork_cleanup_sighand:' label. For copy_process() case it is sufficient
to just backout copy_signal(), nothing more.
Again, nobody can see this task yet. For CLONE_THREAD case we just decrement
signal->count, otherwise nobody can see this ->signal and we can free it
lockless.
This patch assumes it is safe to do exit_thread_group_keys() without
tasklist_lock.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The only caller of exit_sighand(tsk) is copy_process's error path. We can
call __exit_sighand() directly and kill exit_sighand().
This 'tsk' was not yet registered in pid_hash[] or init_task.tasks, it has no
external references, nobody can see it, and
IF (clone_flags & CLONE_SIGHAND)
At least 'current' has a reference to ->sighand, this
means atomic_dec_and_test(sighand->count) can't be true.
ELSE
Nobody can see this ->sighand, this means we can free it
without any locking.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
