Wu Fengguang 70ac23cfa3 readahead: sequential mmap readahead ... Auto-detect sequential mmap reads and do readahead for them. The sequential mmap readahead will be triggered when - sync readahead: it's a major fault and (prev_offset == offset-1); - async readahead: minor fault on PG_readahead page with valid readahead state. The benefits of doing readahead instead of read-around: - less I/O wait thanks to async readahead - double real I/O size and no more cache hits The single stream case is improved a little. For 100,000 sequential mmap reads: user system cpu total (1-1) plain -mm, 128KB readaround: 3.224 2.554 48.40% 11.838 (1-2) plain -mm, 256KB readaround: 3.170 2.392 46.20% 11.976 (2) patched -mm, 128KB readahead: 3.117 2.448 47.33% 11.607 The patched (2) has smallest total time, since it has no cache hit overheads and less I/O block time(thanks to async readahead). Here the I/O size makes no much difference, since there's only one single stream. Note that (1-1)'s real I/O size is 64KB and (1-2)'s real I/O size is 128KB, since the half of the read-around pages will be readahead cache hits. This is going to make _real_ differences for _concurrent_ IO streams. Cc: Nick Piggin <npiggin@suse.de> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Cc: Ying Han <yinghan@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2009-06-16 19:47:29 -07:00
..
allocpercpu.c
backing-dev.c
bootmem.c
bounce.c
debug-pagealloc.c
dmapool.c
fadvise.c
failslab.c
filemap_xip.c
filemap.c	readahead: sequential mmap readahead	2009-06-16 19:47:29 -07:00
fremap.c
highmem.c
hugetlb.c
init-mm.c
internal.h
Kconfig
Kconfig.debug
kmemleak-test.c
kmemleak.c
maccess.c
madvise.c
Makefile
memcontrol.c
memory_hotplug.c
memory.c
mempolicy.c
mempool.c
migrate.c
mincore.c
mlock.c
mm_init.c
mmap.c
mmu_notifier.c
mmzone.c
mprotect.c
mremap.c
msync.c
nommu.c
oom_kill.c
page_alloc.c
page_cgroup.c
page_io.c
page_isolation.c
page-writeback.c
pagewalk.c
pdflush.c
percpu.c
prio_tree.c
quicklist.c
readahead.c	readahead: remove sync/async readahead call dependency	2009-06-16 19:47:29 -07:00
rmap.c
shmem_acl.c
shmem.c
slab.c
slob.c
slub.c
sparse-vmemmap.c
sparse.c
swap_state.c
swap.c
swapfile.c
thrash.c
truncate.c
util.c
vmalloc.c
vmscan.c
vmstat.c