kernel.git/fs/f2fs/checkpoint.c, branch linux-3.14.y

mm: non-atomically mark page accessed during page cache allocation where possible

2015-01-30T01:40:52Z

commit 2457aec63745e235bcafb7ef312b182d8682f0fc upstream. aops->write_begin may allocate a new page and make it visible only to have mark_page_accessed called almost immediately after. Once the page is visible the atomic operations are necessary which is noticable overhead when writing to an in-memory filesystem like tmpfs but should also be noticable with fast storage. The objective of the patch is to initialse the accessed information with non-atomic operations before the page is visible. The bulk of filesystems directly or indirectly use grab_cache_page_write_begin or find_or_create_page for the initial allocation of a page cache page. This patch adds an init_page_accessed() helper which behaves like the first call to mark_page_accessed() but may called before the page is visible and can be done non-atomically. The primary APIs of concern in this care are the following and are used by most filesystems. find_get_page find_lock_page find_or_create_page grab_cache_page_nowait grab_cache_page_write_begin All of them are very similar in detail to the patch creates a core helper pagecache_get_page() which takes a flags parameter that affects its behavior such as whether the page should be marked accessed or not. Then old API is preserved but is basically a thin wrapper around this core function. Each of the filesystems are then updated to avoid calling mark_page_accessed when it is known that the VM interfaces have already done the job. There is a slight snag in that the timing of the mark_page_accessed() has now changed so in rare cases it's possible a page gets to the end of the LRU as PageReferenced where as previously it might have been repromoted. This is expected to be rare but it's worth the filesystem people thinking about it in case they see a problem with the timing change. It is also the case that some filesystems may be marking pages accessed that previously did not but it makes sense that filesystems have consistent behaviour in this regard. The test case used to evaulate this is a simple dd of a large file done multiple times with the file deleted on each iterations. The size of the file is 1/10th physical memory to avoid dirty page balancing. In the async case it will be possible that the workload completes without even hitting the disk and will have variable results but highlight the impact of mark_page_accessed for async IO. The sync results are expected to be more stable. The exception is tmpfs where the normal case is for the "IO" to not hit the disk. The test machine was single socket and UMA to avoid any scheduling or NUMA artifacts. Throughput and wall times are presented for sync IO, only wall times are shown for async as the granularity reported by dd and the variability is unsuitable for comparison. As async results were variable do to writback timings, I'm only reporting the maximum figures. The sync results were stable enough to make the mean and stddev uninteresting. The performance results are reported based on a run with no profiling. Profile data is based on a separate run with oprofile running. async dd 3.15.0-rc3 3.15.0-rc3 vanilla accessed-v2 ext3 Max elapsed 13.9900 ( 0.00%) 11.5900 ( 17.16%) tmpfs Max elapsed 0.5100 ( 0.00%) 0.4900 ( 3.92%) btrfs Max elapsed 12.8100 ( 0.00%) 12.7800 ( 0.23%) ext4 Max elapsed 18.6000 ( 0.00%) 13.3400 ( 28.28%) xfs Max elapsed 12.5600 ( 0.00%) 2.0900 ( 83.36%) The XFS figure is a bit strange as it managed to avoid a worst case by sheer luck but the average figures looked reasonable. samples percentage ext3 86107 0.9783 vmlinux-3.15.0-rc4-vanilla mark_page_accessed ext3 23833 0.2710 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed ext3 5036 0.0573 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed ext4 64566 0.8961 vmlinux-3.15.0-rc4-vanilla mark_page_accessed ext4 5322 0.0713 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed ext4 2869 0.0384 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed xfs 62126 1.7675 vmlinux-3.15.0-rc4-vanilla mark_page_accessed xfs 1904 0.0554 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed xfs 103 0.0030 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed btrfs 10655 0.1338 vmlinux-3.15.0-rc4-vanilla mark_page_accessed btrfs 2020 0.0273 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed btrfs 587 0.0079 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed tmpfs 59562 3.2628 vmlinux-3.15.0-rc4-vanilla mark_page_accessed tmpfs 1210 0.0696 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed tmpfs 94 0.0054 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed [akpm@linux-foundation.org: don't run init_page_accessed() against an uninitialised pointer] Signed-off-by: Mel Gorman Cc: Johannes Weiner Cc: Vlastimil Babka Cc: Jan Kara Cc: Michal Hocko Cc: Hugh Dickins Cc: Dave Hansen Cc: Theodore Ts'o Cc: "Paul E. McKenney" Cc: Oleg Nesterov Cc: Rik van Riel Cc: Peter Zijlstra Tested-by: Prabhakar Lad Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Mel Gorman Signed-off-by: Greg Kroah-Hartman

f2fs: introduce NODE_MAPPING for code consistency

2014-01-22T09:41:08Z

This patch adds NODE_MAPPING which is similar as META_MAPPING introduced by Gu Zheng. Cc: Gu Zheng Signed-off-by: Jaegeuk Kim

f2fs: remove the orphan block page array

2014-01-22T09:41:08Z

As the orphan_blocks may be max to 504, so it is not security and rigorous to store such a large array in the kernel stack as Dan Carpenter said. In fact, grab_meta_page has locked the page in the page cache, and we can use find_get_page() to fetch the page safely in the downstream, so we can remove the page array directly. Reported-by: Dan Carpenter Signed-off-by: Gu Zheng Signed-off-by: Jaegeuk Kim

f2fs: add help function META_MAPPING

2014-01-22T09:41:07Z

Introduce help function META_MAPPING() to get the cache meta blocks' address space. Signed-off-by: Gu Zheng Signed-off-by: Jaegeuk Kim

f2fs: use spinlock rather than mutex for better speed

2014-01-14T09:12:05Z

With the 2 previous changes, all the long time operations are moved out of the protection region, so here we can use spinlock rather than mutex (orphan_inode_mutex) for lower overhead. Signed-off-by: Gu Zheng Signed-off-by: Jaegeuk Kim

f2fs: move alloc new orphan node out of lock protection region

2014-01-14T09:12:04Z

Move alloc new orphan node out of lock protection region. Signed-off-by: Gu Zheng Signed-off-by: Jaegeuk Kim

f2fs: move grabing orphan pages out of protection region

2014-01-14T09:11:20Z

Move grabing orphan block page out of protection region, and grab all the orphan block pages ahead. Signed-off-by: Gu Zheng Reviewed-by: Chao Yu [Jaegeuk Kim: remove unnecessary code pointed by Chao Yu] Signed-off-by: Jaegeuk Kim

f2fs: convert max_orphans to a field of f2fs_sb_info

2013-12-26T11:37:52Z

Previously, we need to calculate the max orphan num when we try to acquire an orphan inode, but it's a stable value since the super block was inited. So converting it to a field of f2fs_sb_info and use it directly when needed seems a better choose. Signed-off-by: Gu Zheng Signed-off-by: Jaegeuk Kim

f2fs: write dirty meta pages collectively

2013-12-23T01:18:07Z

This patch enhances writing dirty meta pages collectively in background. During the file data writes, it'd better avoid to write small dirty meta pages frequently. So let's give a chance to collect a number of dirty meta pages for a while. Signed-off-by: Jaegeuk Kim

f2fs: refactor bio->rw handling

2013-12-23T01:18:06Z

This patch introduces f2fs_io_info to mitigate the complex parameter list. struct f2fs_io_info { enum page_type type; /* contains DATA/NODE/META/META_FLUSH */ int rw; /* contains R/RS/W/WS */ int rw_flag; /* contains REQ_META/REQ_PRIO */ } 1. f2fs_write_data_pages - DATA - WRITE_SYNC is set when wbc->WB_SYNC_ALL. 2. sync_node_pages - NODE - WRITE_SYNC all the time 3. sync_meta_pages - META - WRITE_SYNC all the time - REQ_META | REQ_PRIO all the time ** f2fs_submit_merged_bio() handles META_FLUSH. 4. ra_nat_pages, ra_sit_pages, ra_sum_pages - META - READ_SYNC Cc: Fan Li Cc: Changman Lee Signed-off-by: Jaegeuk Kim