kernel.git/fs/gfs2/aops.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

GFS2: No need to invalidate pages for a dio read

2014-01-14T19:20:49Z

We recently fixed the writeback of pages prior to performing direct i/o, however the initial fix was perhaps a bit heavy handed. There is no need to invalidate pages if the direct i/o is only a read, since they will be identical to what has been flushed to disk anyway. Signed-off-by: Steven Whitehouse

GFS2: Clean up releasepage

2014-01-03T09:58:41Z

For historical reasons, we drop and retake the log lock in ->releasepage() however, since there is no reason why we cannot hold the log lock over the whole function, this allows some simplification. In particular, pinning a buffer is only ever done under the log lock, so it is possible here to remove the test for pinned buffers in the second loop, since it is impossible for that to happen (it is also tested in the first loop). As a result, two tests made later in the second loop become constants and can also be reduced to the only possible branch. So the net result is to remove various bits of unreachable code and make this more readable. Signed-off-by: Steven Whitehouse

GFS2: Fix incorrect invalidation for DIO/buffered I/O

2013-12-20T10:41:21Z

In patch 209806aba9d540dde3db0a5ce72307f85f33468f we allowed local deferred locks to be granted against a cached exclusive lock. That opened up a corner case which this patch now fixes. The solution to the problem is to check whether we have cached pages each time we do direct I/O and if so to unmap, flush and invalidate those pages. Since the glock state machine normally does that for us, mostly the code will be a no-op. Signed-off-by: Steven Whitehouse

GFS2: Add allocation parameters structure

2013-10-02T10:13:25Z

This patch adds a structure to contain allocation parameters with the intention of future expansion of this structure. The idea is that we should be able to add more information about the allocation in the future in order to allow the allocator to make a better job of placing the requests on-disk. There is no functional difference from applying this patch. Signed-off-by: Steven Whitehouse

GFS2: dirty inode correctly in gfs2_write_end

2013-09-05T08:04:24Z

GFS2 was only setting I_DIRTY_DATASYNC on files that it wrote to, when it actually increased the file size. If gfs2_fsync was called without I_DIRTY_DATASYNC set, it didn't flush the incore data to the log before returning, so any metadata or journaled data changes were not getting fsynced. This meant that writes to the middle of files were not always getting fsynced properly. This patch makes gfs2 set I_DIRTY_DATASYNC whenever metadata has been updated during a write. It also make gfs2_sync flush the incore log if I_DIRTY_PAGES is set, and the file is using data journalling. This will make sure that all incore logged data gets written to disk before returning from a fsync. Signed-off-by: Benjamin Marzinski Signed-off-by: Steven Whitehouse

GFS2: Merge ordered and writeback writepage

2013-08-27T20:22:07Z

The writepages function was recently merged between writeback and ordered mode. This completes the change by doing the same with writepage. The remaining differences in writepage were left over from some earlier time and not actually doing anything useful. Signed-off-by: Steven Whitehouse

gfs2: use ->invalidatepage() length argument

2013-05-22T03:58:49Z

->invalidatepage() aop now accepts range to invalidate so we can make use of it in gfs2_invalidatepage(). Signed-off-by: Lukas Czerner Acked-by: Steven Whitehouse Cc: cluster-devel@redhat.com

mm: change invalidatepage prototype to accept length

2013-05-22T03:17:23Z

Currently there is no way to truncate partial page where the end truncate point is not at the end of the page. This is because it was not needed and the functionality was enough for file system truncate operation to work properly. However more file systems now support punch hole feature and it can benefit from mm supporting truncating page just up to the certain point. Specifically, with this functionality truncate_inode_pages_range() can be changed so it supports truncating partial page at the end of the range (currently it will BUG_ON() if 'end' is not at the end of the page). This commit changes the invalidatepage() address space operation prototype to accept range to be invalidated and update all the instances for it. We also change the block_invalidatepage() in the same way and actually make a use of the new length argument implementing range invalidation. Actual file system implementations will follow except the file systems where the changes are really simple and should not change the behaviour in any way .Implementation for truncate_page_range() which will be able to accept page unaligned ranges will follow as well. Signed-off-by: Lukas Czerner Cc: Andrew Morton Cc: Hugh Dickins

aio: don't include aio.h in sched.h

2013-05-08T03:16:25Z

Faster kernel compiles by way of fewer unnecessary includes. [akpm@linux-foundation.org: fix fallout] [akpm@linux-foundation.org: fix build] Signed-off-by: Kent Overstreet Cc: Zach Brown Cc: Felipe Balbi Cc: Greg Kroah-Hartman Cc: Mark Fasheh Cc: Joel Becker Cc: Rusty Russell Cc: Jens Axboe Cc: Asai Thambi S P Cc: Selvan Mani Cc: Sam Bradshaw Cc: Jeff Moyer Cc: Al Viro Cc: Benjamin LaHaise Reviewed-by: "Theodore Ts'o" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds