Damien Ramonda af248a0c67 readahead: fix sequential read cache miss detection ... The kernel's readahead algorithm sometimes interprets random read accesses as sequential and triggers unnecessary data prefecthing from storage device (impacting random read average latency). In order to identify sequential cache read misses, the readahead algorithm intends to check whether offset - previous offset == 1 (trivial sequential reads) or offset - previous offset == 0 (sequential reads not aligned on page boundary): if (offset - (ra->prev_pos >> PAGE_CACHE_SHIFT) <= 1UL) The current offset is stored in the "offset" variable of type "pgoff_t" (unsigned long), while previous offset is stored in "ra->prev_pos" of type "loff_t" (long long). Therefore, operands of the if statement are implicitly converted to type long long. Consequently, when previous offset > current offset (which happens on random pattern), the if condition is true and access is wrongly interpeted as sequential. An unnecessary data prefetching is triggered, impacting the average random read latency. Storing the previous offset value in a "pgoff_t" variable (unsigned long) fixes the sequential read detection logic. Signed-off-by: Damien Ramonda <damien.ramonda@intel.com> Reviewed-by: Fengguang Wu <fengguang.wu@intel.com> Acked-by: Pierre Tardy <pierre.tardy@intel.com> Acked-by: David Cohen <david.a.cohen@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2013-11-13 12:09:09 +09:00
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backing-dev.c	mm/backing-dev.c: check user buffer length before copying data to the related user buffer	2013-09-11 15:58:03 -07:00
balloon_compaction.c
bootmem.c	mm/bootmem.c: remove unused local `map'	2013-11-13 12:09:09 +09:00
bounce.c	mm/bounce.c: fix a regression where MS_SNAP_STABLE (stable pages snapshotting) was ignored	2013-09-30 14:31:02 -07:00
cleancache.c
compaction.c	mm/compaction.c: update comment about zone lock in isolate_freepages_block	2013-11-13 12:09:03 +09:00
debug-pagealloc.c
dmapool.c
fadvise.c
failslab.c
filemap.c	mm: memcg: handle non-error OOM situations more gracefully	2013-10-16 21:35:53 -07:00
filemap_xip.c
fremap.c	mm: save soft-dirty bits on file pages	2013-08-13 17:57:48 -07:00
frontswap.c
highmem.c
huge_memory.c	mm: thp: khugepaged: add policy for finding target node	2013-11-13 12:09:06 +09:00
hugetlb.c	mm: hugetlb: initialize PG_reserved for tail pages of gigantic compound pages	2013-10-16 21:35:52 -07:00
hugetlb_cgroup.c	cgroup: pass around cgroup_subsys_state instead of cgroup in file methods	2013-08-08 20:11:24 -04:00
hwpoison-inject.c	mm/hwpoison: fix the lack of one reference count against poisoned page	2013-09-30 14:31:03 -07:00
init-mm.c
internal.h	mm: vmscan: fix do_try_to_free_pages() livelock	2013-09-11 15:58:01 -07:00
interval_tree.c
Kconfig	mem-hotplug: introduce movable_node boot option	2013-11-13 12:09:09 +09:00
Kconfig.debug
kmemcheck.c
kmemleak-test.c
kmemleak.c	mm: kmemleak: avoid false negatives on vmalloc'ed objects	2013-11-13 12:09:07 +09:00
ksm.c	ksm: remove redundant __GFP_ZERO from kcalloc	2013-11-13 12:09:02 +09:00
list_lru.c	mm: list_lru: fix almost infinite loop causing effective livelock	2013-10-30 12:57:46 -07:00
maccess.c
madvise.c	mm/hwpoison: fix traversal of hugetlbfs pages to avoid printk flood	2013-09-30 14:31:02 -07:00
Makefile	list: add a new LRU list type	2013-09-10 18:56:30 -04:00
memblock.c	mm/memblock.c: introduce bottom-up allocation mode	2013-11-13 12:09:08 +09:00
memcontrol.c	memcg: support hierarchical memory.numa_stats	2013-11-13 12:09:06 +09:00
memory-failure.c	mm/memory-failure.c: move set_migratetype_isolate() outside get_any_page()	2013-11-13 12:09:04 +09:00
memory.c	mm: remove obsolete comments about page table lock	2013-11-13 12:09:03 +09:00
memory_hotplug.c	mem-hotplug: introduce movable_node boot option	2013-11-13 12:09:09 +09:00
mempolicy.c	mm/mempolicy: use NUMA_NO_NODE	2013-11-13 12:09:06 +09:00
mempool.c	mm/mempool.c: convert kmalloc_node(...GFP_ZERO...) to kzalloc_node(...)	2013-09-11 15:58:14 -07:00
migrate.c	Merge branch 'linus' into sched/core	2013-11-01 08:24:41 +01:00
mincore.c
mlock.c	mm/mlock.c: prevent walking off the end of a pagetable in no-pmd configuration	2013-09-30 14:31:02 -07:00
mm_init.c	mm: numa: Change page last {nid,pid} into {cpu,pid}	2013-10-09 14:47:45 +02:00
mmap.c	mmap: arch_get_unmapped_area(): use proper mmap base for bottom up direction	2013-11-13 12:09:08 +09:00
mmu_context.c
mmu_notifier.c
mmzone.c	mm: numa: Change page last {nid,pid} into {cpu,pid}	2013-10-09 14:47:45 +02:00
mprotect.c	Merge branch 'linus' into sched/core	2013-11-01 08:24:41 +01:00
mremap.c	mm: revert mremap pud_free anti-fix	2013-10-16 21:35:53 -07:00
msync.c
nobootmem.c	mm/nobootmem.c: have __free_pages_memory() free in larger chunks.	2013-11-13 12:09:04 +09:00
nommu.c	mm: remove free_area_cache	2013-07-10 18:11:34 -07:00
oom_kill.c	mm: memcg: handle non-error OOM situations more gracefully	2013-10-16 21:35:53 -07:00
page-writeback.c	writeback: fix negative bdi max pause	2013-10-16 21:35:53 -07:00
page_alloc.c	mm/page_alloc.c: remove unused marco LONG_ALIGN	2013-11-13 12:09:07 +09:00
page_cgroup.c
page_io.c	aio: Kill aio_rw_vect_retry()	2013-07-30 11:53:12 -04:00
page_isolation.c	mm: memory-hotplug: enable memory hotplug to handle hugepage	2013-09-11 15:57:48 -07:00
pagewalk.c	mm/pagewalk.c: fix walk_page_range() access of wrong PTEs	2013-10-30 14:27:03 -07:00
percpu-km.c
percpu-vm.c
percpu.c
pgtable-generic.c	mm: move pgtable related functions to right place	2013-09-11 15:57:30 -07:00
process_vm_access.c
quicklist.c
readahead.c	readahead: fix sequential read cache miss detection	2013-11-13 12:09:09 +09:00
rmap.c	thp: account anon transparent huge pages into NR_ANON_PAGES	2013-09-12 15:38:03 -07:00
shmem.c	initmpfs: make rootfs use tmpfs when CONFIG_TMPFS enabled	2013-09-11 15:59:37 -07:00
slab.c	kernel: delete __cpuinit usage from all core kernel files	2013-07-14 19:36:59 -04:00
slab.h	memcg: check that kmem_cache has memcg_params before accessing it	2013-08-28 19:26:38 -07:00
slab_common.c	slab_common: Do not check for duplicate slab names	2013-09-28 09:47:41 +03:00
slob.c	mm/sl[aou]b: Move kmallocXXX functions to common code	2013-09-04 20:51:33 +03:00
slub.c	Merge branch 'slab/next' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/linux	2013-09-15 07:15:06 -04:00
sparse-vmemmap.c
sparse.c	mm/sparsemem: fix a bug in free_map_bootmem when CONFIG_SPARSEMEM_VMEMMAP	2013-11-13 12:09:06 +09:00
swap.c	mm: make lru_add_drain_all() selective	2013-09-12 15:38:02 -07:00
swap_state.c	lib/radix-tree.c: make radix_tree_node_alloc() work correctly within interrupt	2013-09-11 15:59:36 -07:00
swapfile.c	frontswap: enable call to invalidate area on swapoff	2013-11-13 12:09:07 +09:00
truncate.c	truncate: drop 'oldsize' truncate_pagecache() parameter	2013-09-12 15:38:02 -07:00
util.c	swap: clean-up #ifdef in page_mapping()	2013-09-11 15:57:31 -07:00
vmalloc.c	mm: kmemleak: avoid false negatives on vmalloc'ed objects	2013-11-13 12:09:07 +09:00
vmpressure.c	Merge branch 'for-3.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup	2013-09-03 18:25:03 -07:00
vmscan.c	mm/vmscan.c: don't forget to free shrinker->nr_deferred	2013-10-16 21:35:52 -07:00
vmstat.c	mm: clear N_CPU from node_states at CPU offline	2013-11-13 12:09:09 +09:00
zbud.c	mm/zbud: fix some trivial typos in comments	2013-09-11 15:57:35 -07:00
zswap.c	mm/zswap: avoid unnecessary page scanning	2013-11-13 12:09:08 +09:00