BMC/Intel-BMC/linux.git/fs/gfs2/meta_io.c, branch dev

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

2014-06-04T23:54:10+00:00

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

GFS2: Fix address space from page function

2014-03-31T16:48:27+00:00

Now that rgrps use the address space which is part of the super block, we need to update gfs2_mapping2sbd() to take account of that. The only way to do that easily is to use a different set of address_space_operations for rgrps. Reported-by: Abhi Das Tested-by: Abhi Das Signed-off-by: Steven Whitehouse

GFS2: Move log buffer accounting to transaction

2014-02-24T19:49:12+00:00

Now we have a master transaction into which other transactions are merged, the accounting can be done using this master transaction. We no longer require the superblock fields which were being used for this function. In addition, this allows for a clean up in calc_reserved() making it rather easier understand. Also, by reducing the number of variables used to track the buffers being added and removed from the journal, a number of error checks are now no longer required. Signed-off-by: Steven Whitehouse

GFS2: Use only a single address space for rgrps

2014-01-03T10:01:50+00:00

Prior to this patch, GFS2 had one address space for each rgrp, stored in the glock. This patch changes them to use a single address space in the super block. This therefore saves (sizeof(struct address_space) * nr_of_rgrps) bytes of memory and for large filesystems, that can be significant. It would be nice to be able to do something similar and merge the inode metadata address space into the same global address space. However, that is rather more complicated as the on-disk location doesn't have a 1:1 mapping with the inodes in general. So while it could be done, it will be a more complicated operation as it requires changing a lot more code paths. Signed-off-by: Steven Whitehouse

GFS2: Fix slab memory leak in gfs2_bufdata

2013-12-13T21:42:40+00:00

This patch fixes a slab memory leak that sometimes can occur for files with a very short lifespan. The problem occurs when a dinode is deleted before it has gotten to the journal properly. In the leak scenario, the bd object is pinned for journal committment (queued to the metadata buffers queue: sd_log_le_buf) but is subsequently unpinned and dequeued before it finds its way to the ail or the revoke queue. In this rare circumstance, the bd object needs to be freed from slab memory, or it is forgotten. We have to be very careful how we do it, though, because multiple processes can call gfs2_remove_from_journal. In order to avoid double-frees, only the process that does the unpinning is allowed to free the bd. Signed-off-by: Bob Peterson Signed-off-by: Steven Whitehouse

GFS2: Move gfs2_sync_meta to lops.c

2013-08-19T16:26:32+00:00

Since gfs2_sync_meta() is only called from a single file, lets move it to lops.c where it is used, and mark it static. At the same time, we can clean up the meta_io.h header too. Signed-off-by: Steven Whitehouse

GFS2: aggressively issue revokes in gfs2_log_flush

2013-06-19T08:41:59+00:00

This patch looks at all the outstanding blocks in all the transactions on the log, and moves the completed ones to the ail2 list. Then it issues revokes for these blocks. This will hopefully speed things up in situations where there is a lot of contention for glocks, especially if they are acquired serially. revoke_lo_before_commit will issue at most one log block's full of these preemptive revokes. The amount of reserved log space that gfs2_log_reserve() ignores has been incremented to allow for this extra block. This patch also consolidates the common revoke instructions into one function, gfs2_add_revoke(). Signed-off-by: Benjamin Marzinski Signed-off-by: Steven Whitehouse

GFS2: replace gfs2_ail structure with gfs2_trans

2013-04-08T07:46:22+00:00

In order to allow transactions and log flushes to happen at the same time, gfs2 needs to move the transaction accounting and active items list code into the gfs2_trans structure. As a first step toward this, this patch removes the gfs2_ail structure, and handles the active items list in the gfs_trans structure. This keeps gfs2 from allocating an ail structure on log flushes, and gives us a struture that can later be used to store the transaction accounting outside of the gfs2 superblock structure. With this patch, at the end of a transaction, gfs2 will add the gfs2_trans structure to the superblock if there is not one already. This structure now has the active items fields that were previously in gfs2_ail. This is not necessary in the case where the transaction was simply used to add revokes, since these are never written outside of the journal, and thus, don't need an active items list. Also, in order to make sure that the transaction structure is not removed while it's still in use by gfs2_trans_end, unlocking the sd_log_flush_lock has to happen slightly later in ending the transaction. Signed-off-by: Benjamin Marzinski Signed-off-by: Steven Whitehouse

GFS2: Merge gfs2_attach_bufdata() into trans.c

2013-01-29T10:28:44+00:00

The locking in gfs2_attach_bufdata() was type specific (data/meta) which made the function rather confusing. This patch moves the core of gfs2_attach_bufdata() into trans.c renaming it gfs2_alloc_bufdata() and moving the locking into gfs2_trans_add_data()/gfs2_trans_add_meta() As a result all of the locking related to adding data and metadata to the journal is now in these two functions. This should help to clarify what is going on, and give us some opportunities to simplify in some cases. Signed-off-by: Steven Whitehouse

gfs2: nuke pdflush from comments

2012-08-04T08:15:40+00:00

The pdflush thread is long gone, so this patch removes references to pdflush from gfs comments. Cc: Steven Whitehouse Signed-off-by: Artem Bityutskiy Signed-off-by: Al Viro