|
|
|
@ -2161,11 +2161,73 @@ unsigned long this_cpu_load(void)
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Global load-average calculations
|
|
|
|
|
*
|
|
|
|
|
* We take a distributed and async approach to calculating the global load-avg
|
|
|
|
|
* in order to minimize overhead.
|
|
|
|
|
*
|
|
|
|
|
* The global load average is an exponentially decaying average of nr_running +
|
|
|
|
|
* nr_uninterruptible.
|
|
|
|
|
*
|
|
|
|
|
* Once every LOAD_FREQ:
|
|
|
|
|
*
|
|
|
|
|
* nr_active = 0;
|
|
|
|
|
* for_each_possible_cpu(cpu)
|
|
|
|
|
* nr_active += cpu_of(cpu)->nr_running + cpu_of(cpu)->nr_uninterruptible;
|
|
|
|
|
*
|
|
|
|
|
* avenrun[n] = avenrun[0] * exp_n + nr_active * (1 - exp_n)
|
|
|
|
|
*
|
|
|
|
|
* Due to a number of reasons the above turns in the mess below:
|
|
|
|
|
*
|
|
|
|
|
* - for_each_possible_cpu() is prohibitively expensive on machines with
|
|
|
|
|
* serious number of cpus, therefore we need to take a distributed approach
|
|
|
|
|
* to calculating nr_active.
|
|
|
|
|
*
|
|
|
|
|
* \Sum_i x_i(t) = \Sum_i x_i(t) - x_i(t_0) | x_i(t_0) := 0
|
|
|
|
|
* = \Sum_i { \Sum_j=1 x_i(t_j) - x_i(t_j-1) }
|
|
|
|
|
*
|
|
|
|
|
* So assuming nr_active := 0 when we start out -- true per definition, we
|
|
|
|
|
* can simply take per-cpu deltas and fold those into a global accumulate
|
|
|
|
|
* to obtain the same result. See calc_load_fold_active().
|
|
|
|
|
*
|
|
|
|
|
* Furthermore, in order to avoid synchronizing all per-cpu delta folding
|
|
|
|
|
* across the machine, we assume 10 ticks is sufficient time for every
|
|
|
|
|
* cpu to have completed this task.
|
|
|
|
|
*
|
|
|
|
|
* This places an upper-bound on the IRQ-off latency of the machine. Then
|
|
|
|
|
* again, being late doesn't loose the delta, just wrecks the sample.
|
|
|
|
|
*
|
|
|
|
|
* - cpu_rq()->nr_uninterruptible isn't accurately tracked per-cpu because
|
|
|
|
|
* this would add another cross-cpu cacheline miss and atomic operation
|
|
|
|
|
* to the wakeup path. Instead we increment on whatever cpu the task ran
|
|
|
|
|
* when it went into uninterruptible state and decrement on whatever cpu
|
|
|
|
|
* did the wakeup. This means that only the sum of nr_uninterruptible over
|
|
|
|
|
* all cpus yields the correct result.
|
|
|
|
|
*
|
|
|
|
|
* This covers the NO_HZ=n code, for extra head-aches, see the comment below.
|
|
|
|
|
*/
|
|
|
|
|
|
|
|
|
|
/* Variables and functions for calc_load */
|
|
|
|
|
static atomic_long_t calc_load_tasks;
|
|
|
|
|
static unsigned long calc_load_update;
|
|
|
|
|
unsigned long avenrun[3];
|
|
|
|
|
EXPORT_SYMBOL(avenrun);
|
|
|
|
|
EXPORT_SYMBOL(avenrun); /* should be removed */
|
|
|
|
|
|
|
|
|
|
/**
|
|
|
|
|
* get_avenrun - get the load average array
|
|
|
|
|
* @loads: pointer to dest load array
|
|
|
|
|
* @offset: offset to add
|
|
|
|
|
* @shift: shift count to shift the result left
|
|
|
|
|
*
|
|
|
|
|
* These values are estimates at best, so no need for locking.
|
|
|
|
|
*/
|
|
|
|
|
void get_avenrun(unsigned long *loads, unsigned long offset, int shift)
|
|
|
|
|
{
|
|
|
|
|
loads[0] = (avenrun[0] + offset) << shift;
|
|
|
|
|
loads[1] = (avenrun[1] + offset) << shift;
|
|
|
|
|
loads[2] = (avenrun[2] + offset) << shift;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static long calc_load_fold_active(struct rq *this_rq)
|
|
|
|
|
{
|
|
|
|
@ -2182,6 +2244,9 @@ static long calc_load_fold_active(struct rq *this_rq)
|
|
|
|
|
return delta;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* a1 = a0 * e + a * (1 - e)
|
|
|
|
|
*/
|
|
|
|
|
static unsigned long
|
|
|
|
|
calc_load(unsigned long load, unsigned long exp, unsigned long active)
|
|
|
|
|
{
|
|
|
|
@ -2193,30 +2258,118 @@ calc_load(unsigned long load, unsigned long exp, unsigned long active)
|
|
|
|
|
|
|
|
|
|
#ifdef CONFIG_NO_HZ
|
|
|
|
|
/*
|
|
|
|
|
* For NO_HZ we delay the active fold to the next LOAD_FREQ update.
|
|
|
|
|
* Handle NO_HZ for the global load-average.
|
|
|
|
|
*
|
|
|
|
|
* Since the above described distributed algorithm to compute the global
|
|
|
|
|
* load-average relies on per-cpu sampling from the tick, it is affected by
|
|
|
|
|
* NO_HZ.
|
|
|
|
|
*
|
|
|
|
|
* The basic idea is to fold the nr_active delta into a global idle-delta upon
|
|
|
|
|
* entering NO_HZ state such that we can include this as an 'extra' cpu delta
|
|
|
|
|
* when we read the global state.
|
|
|
|
|
*
|
|
|
|
|
* Obviously reality has to ruin such a delightfully simple scheme:
|
|
|
|
|
*
|
|
|
|
|
* - When we go NO_HZ idle during the window, we can negate our sample
|
|
|
|
|
* contribution, causing under-accounting.
|
|
|
|
|
*
|
|
|
|
|
* We avoid this by keeping two idle-delta counters and flipping them
|
|
|
|
|
* when the window starts, thus separating old and new NO_HZ load.
|
|
|
|
|
*
|
|
|
|
|
* The only trick is the slight shift in index flip for read vs write.
|
|
|
|
|
*
|
|
|
|
|
* 0s 5s 10s 15s
|
|
|
|
|
* +10 +10 +10 +10
|
|
|
|
|
* |-|-----------|-|-----------|-|-----------|-|
|
|
|
|
|
* r:0 0 1 1 0 0 1 1 0
|
|
|
|
|
* w:0 1 1 0 0 1 1 0 0
|
|
|
|
|
*
|
|
|
|
|
* This ensures we'll fold the old idle contribution in this window while
|
|
|
|
|
* accumlating the new one.
|
|
|
|
|
*
|
|
|
|
|
* - When we wake up from NO_HZ idle during the window, we push up our
|
|
|
|
|
* contribution, since we effectively move our sample point to a known
|
|
|
|
|
* busy state.
|
|
|
|
|
*
|
|
|
|
|
* This is solved by pushing the window forward, and thus skipping the
|
|
|
|
|
* sample, for this cpu (effectively using the idle-delta for this cpu which
|
|
|
|
|
* was in effect at the time the window opened). This also solves the issue
|
|
|
|
|
* of having to deal with a cpu having been in NOHZ idle for multiple
|
|
|
|
|
* LOAD_FREQ intervals.
|
|
|
|
|
*
|
|
|
|
|
* When making the ILB scale, we should try to pull this in as well.
|
|
|
|
|
*/
|
|
|
|
|
static atomic_long_t calc_load_tasks_idle;
|
|
|
|
|
static atomic_long_t calc_load_idle[2];
|
|
|
|
|
static int calc_load_idx;
|
|
|
|
|
|
|
|
|
|
void calc_load_account_idle(struct rq *this_rq)
|
|
|
|
|
static inline int calc_load_write_idx(void)
|
|
|
|
|
{
|
|
|
|
|
int idx = calc_load_idx;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* See calc_global_nohz(), if we observe the new index, we also
|
|
|
|
|
* need to observe the new update time.
|
|
|
|
|
*/
|
|
|
|
|
smp_rmb();
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* If the folding window started, make sure we start writing in the
|
|
|
|
|
* next idle-delta.
|
|
|
|
|
*/
|
|
|
|
|
if (!time_before(jiffies, calc_load_update))
|
|
|
|
|
idx++;
|
|
|
|
|
|
|
|
|
|
return idx & 1;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static inline int calc_load_read_idx(void)
|
|
|
|
|
{
|
|
|
|
|
return calc_load_idx & 1;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
void calc_load_enter_idle(void)
|
|
|
|
|
{
|
|
|
|
|
struct rq *this_rq = this_rq();
|
|
|
|
|
long delta;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* We're going into NOHZ mode, if there's any pending delta, fold it
|
|
|
|
|
* into the pending idle delta.
|
|
|
|
|
*/
|
|
|
|
|
delta = calc_load_fold_active(this_rq);
|
|
|
|
|
if (delta)
|
|
|
|
|
atomic_long_add(delta, &calc_load_tasks_idle);
|
|
|
|
|
if (delta) {
|
|
|
|
|
int idx = calc_load_write_idx();
|
|
|
|
|
atomic_long_add(delta, &calc_load_idle[idx]);
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
void calc_load_exit_idle(void)
|
|
|
|
|
{
|
|
|
|
|
struct rq *this_rq = this_rq();
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* If we're still before the sample window, we're done.
|
|
|
|
|
*/
|
|
|
|
|
if (time_before(jiffies, this_rq->calc_load_update))
|
|
|
|
|
return;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* We woke inside or after the sample window, this means we're already
|
|
|
|
|
* accounted through the nohz accounting, so skip the entire deal and
|
|
|
|
|
* sync up for the next window.
|
|
|
|
|
*/
|
|
|
|
|
this_rq->calc_load_update = calc_load_update;
|
|
|
|
|
if (time_before(jiffies, this_rq->calc_load_update + 10))
|
|
|
|
|
this_rq->calc_load_update += LOAD_FREQ;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static long calc_load_fold_idle(void)
|
|
|
|
|
{
|
|
|
|
|
int idx = calc_load_read_idx();
|
|
|
|
|
long delta = 0;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Its got a race, we don't care...
|
|
|
|
|
*/
|
|
|
|
|
if (atomic_long_read(&calc_load_tasks_idle))
|
|
|
|
|
delta = atomic_long_xchg(&calc_load_tasks_idle, 0);
|
|
|
|
|
if (atomic_long_read(&calc_load_idle[idx]))
|
|
|
|
|
delta = atomic_long_xchg(&calc_load_idle[idx], 0);
|
|
|
|
|
|
|
|
|
|
return delta;
|
|
|
|
|
}
|
|
|
|
@ -2302,66 +2455,39 @@ static void calc_global_nohz(void)
|
|
|
|
|
{
|
|
|
|
|
long delta, active, n;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* If we crossed a calc_load_update boundary, make sure to fold
|
|
|
|
|
* any pending idle changes, the respective CPUs might have
|
|
|
|
|
* missed the tick driven calc_load_account_active() update
|
|
|
|
|
* due to NO_HZ.
|
|
|
|
|
*/
|
|
|
|
|
delta = calc_load_fold_idle();
|
|
|
|
|
if (delta)
|
|
|
|
|
atomic_long_add(delta, &calc_load_tasks);
|
|
|
|
|
if (!time_before(jiffies, calc_load_update + 10)) {
|
|
|
|
|
/*
|
|
|
|
|
* Catch-up, fold however many we are behind still
|
|
|
|
|
*/
|
|
|
|
|
delta = jiffies - calc_load_update - 10;
|
|
|
|
|
n = 1 + (delta / LOAD_FREQ);
|
|
|
|
|
|
|
|
|
|
active = atomic_long_read(&calc_load_tasks);
|
|
|
|
|
active = active > 0 ? active * FIXED_1 : 0;
|
|
|
|
|
|
|
|
|
|
avenrun[0] = calc_load_n(avenrun[0], EXP_1, active, n);
|
|
|
|
|
avenrun[1] = calc_load_n(avenrun[1], EXP_5, active, n);
|
|
|
|
|
avenrun[2] = calc_load_n(avenrun[2], EXP_15, active, n);
|
|
|
|
|
|
|
|
|
|
calc_load_update += n * LOAD_FREQ;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* It could be the one fold was all it took, we done!
|
|
|
|
|
* Flip the idle index...
|
|
|
|
|
*
|
|
|
|
|
* Make sure we first write the new time then flip the index, so that
|
|
|
|
|
* calc_load_write_idx() will see the new time when it reads the new
|
|
|
|
|
* index, this avoids a double flip messing things up.
|
|
|
|
|
*/
|
|
|
|
|
if (time_before(jiffies, calc_load_update + 10))
|
|
|
|
|
return;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Catch-up, fold however many we are behind still
|
|
|
|
|
*/
|
|
|
|
|
delta = jiffies - calc_load_update - 10;
|
|
|
|
|
n = 1 + (delta / LOAD_FREQ);
|
|
|
|
|
|
|
|
|
|
active = atomic_long_read(&calc_load_tasks);
|
|
|
|
|
active = active > 0 ? active * FIXED_1 : 0;
|
|
|
|
|
|
|
|
|
|
avenrun[0] = calc_load_n(avenrun[0], EXP_1, active, n);
|
|
|
|
|
avenrun[1] = calc_load_n(avenrun[1], EXP_5, active, n);
|
|
|
|
|
avenrun[2] = calc_load_n(avenrun[2], EXP_15, active, n);
|
|
|
|
|
|
|
|
|
|
calc_load_update += n * LOAD_FREQ;
|
|
|
|
|
}
|
|
|
|
|
#else
|
|
|
|
|
void calc_load_account_idle(struct rq *this_rq)
|
|
|
|
|
{
|
|
|
|
|
smp_wmb();
|
|
|
|
|
calc_load_idx++;
|
|
|
|
|
}
|
|
|
|
|
#else /* !CONFIG_NO_HZ */
|
|
|
|
|
|
|
|
|
|
static inline long calc_load_fold_idle(void)
|
|
|
|
|
{
|
|
|
|
|
return 0;
|
|
|
|
|
}
|
|
|
|
|
static inline long calc_load_fold_idle(void) { return 0; }
|
|
|
|
|
static inline void calc_global_nohz(void) { }
|
|
|
|
|
|
|
|
|
|
static void calc_global_nohz(void)
|
|
|
|
|
{
|
|
|
|
|
}
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
/**
|
|
|
|
|
* get_avenrun - get the load average array
|
|
|
|
|
* @loads: pointer to dest load array
|
|
|
|
|
* @offset: offset to add
|
|
|
|
|
* @shift: shift count to shift the result left
|
|
|
|
|
*
|
|
|
|
|
* These values are estimates at best, so no need for locking.
|
|
|
|
|
*/
|
|
|
|
|
void get_avenrun(unsigned long *loads, unsigned long offset, int shift)
|
|
|
|
|
{
|
|
|
|
|
loads[0] = (avenrun[0] + offset) << shift;
|
|
|
|
|
loads[1] = (avenrun[1] + offset) << shift;
|
|
|
|
|
loads[2] = (avenrun[2] + offset) << shift;
|
|
|
|
|
}
|
|
|
|
|
#endif /* CONFIG_NO_HZ */
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* calc_load - update the avenrun load estimates 10 ticks after the
|
|
|
|
@ -2369,11 +2495,18 @@ void get_avenrun(unsigned long *loads, unsigned long offset, int shift)
|
|
|
|
|
*/
|
|
|
|
|
void calc_global_load(unsigned long ticks)
|
|
|
|
|
{
|
|
|
|
|
long active;
|
|
|
|
|
long active, delta;
|
|
|
|
|
|
|
|
|
|
if (time_before(jiffies, calc_load_update + 10))
|
|
|
|
|
return;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Fold the 'old' idle-delta to include all NO_HZ cpus.
|
|
|
|
|
*/
|
|
|
|
|
delta = calc_load_fold_idle();
|
|
|
|
|
if (delta)
|
|
|
|
|
atomic_long_add(delta, &calc_load_tasks);
|
|
|
|
|
|
|
|
|
|
active = atomic_long_read(&calc_load_tasks);
|
|
|
|
|
active = active > 0 ? active * FIXED_1 : 0;
|
|
|
|
|
|
|
|
|
@ -2384,12 +2517,7 @@ void calc_global_load(unsigned long ticks)
|
|
|
|
|
calc_load_update += LOAD_FREQ;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Account one period with whatever state we found before
|
|
|
|
|
* folding in the nohz state and ageing the entire idle period.
|
|
|
|
|
*
|
|
|
|
|
* This avoids loosing a sample when we go idle between
|
|
|
|
|
* calc_load_account_active() (10 ticks ago) and now and thus
|
|
|
|
|
* under-accounting.
|
|
|
|
|
* In case we idled for multiple LOAD_FREQ intervals, catch up in bulk.
|
|
|
|
|
*/
|
|
|
|
|
calc_global_nohz();
|
|
|
|
|
}
|
|
|
|
@ -2406,13 +2534,16 @@ static void calc_load_account_active(struct rq *this_rq)
|
|
|
|
|
return;
|
|
|
|
|
|
|
|
|
|
delta = calc_load_fold_active(this_rq);
|
|
|
|
|
delta += calc_load_fold_idle();
|
|
|
|
|
if (delta)
|
|
|
|
|
atomic_long_add(delta, &calc_load_tasks);
|
|
|
|
|
|
|
|
|
|
this_rq->calc_load_update += LOAD_FREQ;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* End of global load-average stuff
|
|
|
|
|
*/
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* The exact cpuload at various idx values, calculated at every tick would be
|
|
|
|
|
* load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
|
|
|
|
|