kernel_samsung_sm7125

jenna

History

Hisashi Hifumi 8ab22b9abb vfs: pagecache usage optimization for pagesize!=blocksize When we read some part of a file through pagecache, if there is a pagecache of corresponding index but this page is not uptodate, read IO is issued and this page will be uptodate. I think this is good for pagesize == blocksize environment but there is room for improvement on pagesize != blocksize environment. Because in this case a page can have multiple buffers and even if a page is not uptodate, some buffers can be uptodate. So I suggest that when all buffers which correspond to a part of a file that we want to read are uptodate, use this pagecache and copy data from this pagecache to user buffer even if a page is not uptodate. This can reduce read IO and improve system throughput. I wrote a benchmark program and got result number with this program. This benchmark do: 1: mount and open a test file. 2: create a 512MB file. 3: close a file and umount. 4: mount and again open a test file. 5: pwrite randomly 300000 times on a test file. offset is aligned by IO size(1024bytes). 6: measure time of preading randomly 100000 times on a test file. The result was: 2.6.26 330 sec 2.6.26-patched 226 sec Arch:i386 Filesystem:ext3 Blocksize:1024 bytes Memory: 1GB On ext3/4, a file is written through buffer/block. So random read/write mixed workloads or random read after random write workloads are optimized with this patch under pagesize != blocksize environment. This test result showed this. The benchmark program is as follows: #include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <time.h> #include <stdlib.h> #include <string.h> #include <sys/mount.h> #define LEN 1024 #define LOOP 1024512 / 512MB / main(void) { unsigned long i, offset, filesize; int fd; char buf[LEN]; time_t t1, t2; if (mount("/dev/sda1", "/root/test1/", "ext3", 0, 0) < 0) { perror("cannot mount\n"); exit(1); } memset(buf, 0, LEN); fd = open("/root/test1/testfile", O_CREAT\|O_RDWR\|O_TRUNC); if (fd < 0) { perror("cannot open file\n"); exit(1); } for (i = 0; i < LOOP; i++) write(fd, buf, LEN); close(fd); if (umount("/root/test1/") < 0) { perror("cannot umount\n"); exit(1); } if (mount("/dev/sda1", "/root/test1/", "ext3", 0, 0) < 0) { perror("cannot mount\n"); exit(1); } fd = open("/root/test1/testfile", O_RDWR); if (fd < 0) { perror("cannot open file\n"); exit(1); } filesize = LEN LOOP; for (i = 0; i < 300000; i++){ offset = (random() % filesize) & (~(LEN - 1)); pwrite(fd, buf, LEN, offset); } printf("start test\n"); time(&t1); for (i = 0; i < 100000; i++){ offset = (random() % filesize) & (~(LEN - 1)); pread(fd, buf, LEN, offset); } time(&t2); printf("%ld sec\n", t2-t1); close(fd); if (umount("/root/test1/") < 0) { perror("cannot umount\n"); exit(1); } } Signed-off-by: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Christoph Hellwig <hch@infradead.org> Cc: Jan Kara <jack@ucw.cz> Cc: <linux-ext4@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		17 years ago
..
Kconfig	mmu-notifiers: core	17 years ago
Makefile	mmu-notifiers: core	17 years ago
allocpercpu.c	mm/allocpercpu.c: make 4 functions static	17 years ago
backing-dev.c	mm: bdi: fix race in bdi_class device creation	17 years ago
bootmem.c	bootmem: replace node_boot_start in struct bootmem_data	17 years ago
bounce.c	…
dmapool.c	dmapool: enable debugging for CONFIG_SLUB_DEBUG_ON too	17 years ago
fadvise.c	xip: support non-struct page backed memory	17 years ago
filemap.c	vfs: pagecache usage optimization for pagesize!=blocksize	17 years ago
filemap_xip.c	mmu-notifiers: core	17 years ago
fremap.c	mmu-notifiers: core	17 years ago
highmem.c	highmem: Export totalhigh_pages.	17 years ago
hugetlb.c	mm/hugetlb.c must #include <asm/io.h>	17 years ago
internal.h	mm: export prep_compound_page to mm	17 years ago
maccess.c	kgdb: fix optional arch functions and probe_kernel_*	17 years ago
madvise.c	xip: support non-struct page backed memory	17 years ago
memcontrol.c	memcg: limit change shrink usage	17 years ago
memory.c	mmu-notifiers: core	17 years ago
memory_hotplug.c	memory-hotplug: add sysfs removable attribute for hotplug memory remove	17 years ago
mempolicy.c	hugetlb: modular state for hugetlb page size	17 years ago
mempool.c	…
migrate.c	mm: spinlock tree_lock	17 years ago
mincore.c	mm: remove nopage	17 years ago
mlock.c	…
mm_init.c	mm: create /sys/kernel/mm	17 years ago
mmap.c	mmu-notifiers: core	17 years ago
mmu_notifier.c	mmu-notifiers: core	17 years ago
mmzone.c	mm: filter based on a nodemask as well as a gfp_mask	17 years ago
mprotect.c	mmu-notifiers: core	17 years ago
mremap.c	mmu-notifiers: core	17 years ago
msync.c	…
nommu.c	tracehook: tracehook_expect_breakpoints	17 years ago
oom_kill.c	oom_kill: remove unused parameter in badness()	17 years ago
page-writeback.c	mm: spinlock tree_lock	17 years ago
page_alloc.c	stop_machine: Wean existing callers off stop_machine_run()	17 years ago
page_io.c	mm: fix PageUptodate data race	17 years ago
page_isolation.c	…
pagewalk.c	pagemap: pass mm into pagewalkers	17 years ago
pdflush.c	pdflush: use time_after() instead of open-coding it	17 years ago
prio_tree.c	…
quicklist.c	…
readahead.c	mm: readahead scan lockless	17 years ago
rmap.c	mmu-notifiers: core	17 years ago
shmem.c	tmpfs: fix kernel BUG in shmem_delete_inode	17 years ago
shmem_acl.c	[PATCH] sanitize ->permission() prototype	17 years ago
slab.c	SL*B: drop kmem cache argument from constructor	17 years ago
slob.c	SL*B: drop kmem cache argument from constructor	17 years ago
slub.c	SL*B: drop kmem cache argument from constructor	17 years ago
sparse-vmemmap.c	Christoph has moved	17 years ago
sparse.c	make mm/sparse.c: make a function static	17 years ago
swap.c	mm: remove initialization of static per-cpu variables	17 years ago
swap_state.c	mm: print swapcache page count in show_swap_cache_info()	17 years ago
swapfile.c	mm/swapfile.c: make code static	17 years ago
thrash.c	…
tiny-shmem.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6	17 years ago
truncate.c	mm: spinlock tree_lock	17 years ago
util.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6	17 years ago
vmalloc.c	Use WARN() in mm/vmalloc.c	17 years ago
vmscan.c	mm: spinlock tree_lock	17 years ago
vmstat.c	mm/vmstat.c: proper externs	17 years ago