diff options
| author | Dave Chinner <[email protected]> | 2010-08-24 11:44:34 +1000 |
|---|---|---|
| committer | Dave Chinner <[email protected]> | 2010-08-24 11:44:34 +1000 |
| commit | 546a1924224078c6f582e68f890b05b387b42653 (patch) | |
| tree | f863df4fd74f85c8177d9eb1467a351cd6d0acfc /net/unix/sysctl_net_unix.c | |
| parent | 4536f2ad8b330453d7ebec0746c4374eadd649b1 (diff) | |
writeback: write_cache_pages doesn't terminate at nr_to_write <= 0
I noticed XFS writeback in 2.6.36-rc1 was much slower than it should have
been. Enabling writeback tracing showed:
flush-253:16-8516 [007] 1342952.351608: wbc_writepage: bdi 253:16: towrt=1024 skip=0 mode=0 kupd=0 bgrd=1 reclm=0 cyclic=1 more=0 older=0x0 start=0x0 end=0x0
flush-253:16-8516 [007] 1342952.351654: wbc_writepage: bdi 253:16: towrt=1023 skip=0 mode=0 kupd=0 bgrd=1 reclm=0 cyclic=1 more=0 older=0x0 start=0x0 end=0x0
flush-253:16-8516 [000] 1342952.369520: wbc_writepage: bdi 253:16: towrt=0 skip=0 mode=0 kupd=0 bgrd=1 reclm=0 cyclic=1 more=0 older=0x0 start=0x0 end=0x0
flush-253:16-8516 [000] 1342952.369542: wbc_writepage: bdi 253:16: towrt=-1 skip=0 mode=0 kupd=0 bgrd=1 reclm=0 cyclic=1 more=0 older=0x0 start=0x0 end=0x0
flush-253:16-8516 [000] 1342952.369549: wbc_writepage: bdi 253:16: towrt=-2 skip=0 mode=0 kupd=0 bgrd=1 reclm=0 cyclic=1 more=0 older=0x0 start=0x0 end=0x0
Writeback is not terminating in background writeback if ->writepage is
returning with wbc->nr_to_write == 0, resulting in sub-optimal single page
writeback on XFS.
Fix the write_cache_pages loop to terminate correctly when this situation
occurs and so prevent this sub-optimal background writeback pattern. This
improves sustained sequential buffered write performance from around
250MB/s to 750MB/s for a 100GB file on an XFS filesystem on my 8p test VM.
Cc:<[email protected]>
Signed-off-by: Dave Chinner <[email protected]>
Reviewed-by: Wu Fengguang <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Diffstat (limited to 'net/unix/sysctl_net_unix.c')
0 files changed, 0 insertions, 0 deletions