On Tue, Aug 16, 2016 at 07:22:40AM +1000, Dave Chinner wrote:
On Mon, Aug 15, 2016 at 10:14:55PM +0800, Fengguang Wu wrote:
Hi Christoph,
On Sun, Aug 14, 2016 at 06:17:24PM +0200, Christoph Hellwig wrote:
>Snipping the long contest:
>
>I think there are three observations here:
>
>(1) removing the mark_page_accessed (which is the only significant
> change in the parent commit) hurts the
> aim7/1BRD_48G-xfs-disk_rr-3000-performance/ivb44 test.
> I'd still rather stick to the filemap version and let the
> VM people sort it out. How do the numbers for this test
> look for XFS vs say ext4 and btrfs?
>(2) lots of additional spinlock contention in the new case. A quick
> check shows that I fat-fingered my rewrite so that we do
> the xfs_inode_set_eofblocks_tag call now for the pure lookup
> case, and pretty much all new cycles come from that.
>(3) Boy, are those xfs_inode_set_eofblocks_tag calls expensive, and
> we're already doing way to many even without my little bug above.
>
>So I've force pushed a new version of the iomap-fixes branch with
>(2) fixed, and also a little patch to xfs_inode_set_eofblocks_tag a
>lot less expensive slotted in before that. Would be good to see
>the numbers with that.
The aim7 1BRD tests finished and there are ups and downs, with overall
performance remain flat.
99091700659f4df9 74a242ad94d13436a1644c0b45 bf4dc6e4ecc2a3d042029319bc
testcase/testparams/testbox
---------------- -------------------------- --------------------------
---------------------------
What do these commits refer to, please? They mean nothing without
the commit names....
/me goes searching. Ok:
99091700659 is the top of Linus' tree
74a242ad94d is ????
That's the below one's parent commit, 74a242ad94d ("xfs: make
xfs_inode_set_eofblocks_tag cheaper for the common case").
Typically we'll compare a commit with its parent commit, and/or
the branch's base commit, which is normally on mainline kernel.
bf4dc6e4ecc is the latest in Christoph's tree (because it's
mentioned below)
%stddev %change %stddev %change %stddev
\ | \ |
\ 159926 157324 158574
GEO-MEAN aim7.jobs-per-min
70897 5% 74137 4% 73775
aim7/1BRD_48G-xfs-creat-clo-1500-performance/ivb44
485217 ± 3% 492431 477533
aim7/1BRD_48G-xfs-disk_rd-9000-performance/ivb44
360451 -19% 292980 -17% 299377
aim7/1BRD_48G-xfs-disk_rr-3000-performance/ivb44
So, why does random read go backwards by 20%? The iomap IO path
patches we are testing only affect the write path, so this
doesn't make a whole lot of sense.
338114 338410 5% 354078
aim7/1BRD_48G-xfs-disk_rw-3000-performance/ivb44
60130 ± 5% 4% 62438 5% 62923
aim7/1BRD_48G-xfs-disk_src-3000-performance/ivb44
403144 397790 410648
aim7/1BRD_48G-xfs-disk_wrt-3000-performance/ivb44
And this is the test the original regression was reported for:
gcc-6/performance/profile/1BRD_48G/xfs/x86_64-rhel/3000/debian-x86_64-2015-02-07.cgz/ivb44/disk_wrt/aim7
And that shows no improvement at all. The orginal regression was:
484435 ± 0% -13.3% 420004 ± 0% aim7.jobs-per-min
So it's still 15% down on the orginal performance which, again,
doesn't make a whole lot of sense given the improvement in so many
other tests I've run....
Yes, same performance with 4.8-rc1 means the regression is still not
back comparing to the original reported first-bad-commit's parent
f0c6bcba74ac51cb ("xfs: reorder zeroing and flushing sequence in
truncate") which is on 4.7-rc1.
26327 26534 26128
aim7/1BRD_48G-xfs-sync_disk_rw-600-performance/ivb44
The new commit bf4dc6e ("xfs: rewrite and optimize the delalloc write
path") improves the aim7/1BRD_48G-xfs-disk_rw-3000-performance/ivb44
case by 5%. Here are the detailed numbers:
aim7/1BRD_48G-xfs-disk_rw-3000-performance/ivb44
Not important at all. We need the results for the disk_wrt regression
we are chasing (disk_wrt-3000) so we can see how the code change
affected behaviour.
Yeah it may not relevant to this case study, however should help
evaluate the patch in a more complete way.
Here are the detailed numbers for the slowed down case:
aim7/1BRD_48G-xfs-disk_rr-3000-performance/ivb44
99091700659f4df9 bf4dc6e4ecc2a3d042029319bc
---------------- --------------------------
%stddev change %stddev
\ | \
360451 -17% 299377 aim7.jobs-per-min
12806 481% 74447
aim7.time.involuntary_context_switches
.....
19377 459% 108364 vmstat.system.cs
.....
487 ± 89% 3e+04 26448 ± 57%
latency_stats.max.down.xfs_buf_lock._xfs_buf_find.xfs_buf_get_map.xfs_buf_read_map.xfs_trans_read_buf_map.xfs_read_agf.xfs_alloc_read_agf.xfs_alloc_fix_freelist.xfs_free_extent_fix_freelist.xfs_free_extent.xfs_trans_free_extent
1823 ± 82% 2e+06 1913796 ± 38%
latency_stats.sum.down.xfs_buf_lock._xfs_buf_find.xfs_buf_get_map.xfs_buf_read_map.xfs_trans_read_buf_map.xfs_read_agf.xfs_alloc_read_agf.xfs_alloc_fix_freelist.xfs_free_extent_fix_freelist.xfs_free_extent.xfs_trans_free_extent
208475 ± 43% 1e+06 1409494 ± 5%
latency_stats.sum.wait_on_page_bit.truncate_inode_pages_range.truncate_inode_pages_final.evict.iput.dentry_unlink_inode.__dentry_kill.dput.__fput.____fput.task_work_run.exit_to_usermode_loop
6884 ± 73% 8e+04 90790 ± 9%
latency_stats.sum.call_rwsem_down_read_failed.xfs_log_commit_cil.__xfs_trans_commit.xfs_trans_commit.xfs_vn_update_time.file_update_time.xfs_file_aio_write_checks.xfs_file_buffered_aio_write.xfs_file_write_iter.__vfs_write.vfs_write.SyS_write
1598 ± 20% 3e+04 35015 ± 27%
latency_stats.sum.call_rwsem_down_read_failed.xfs_log_commit_cil.__xfs_trans_commit.__xfs_trans_roll.xfs_trans_roll.xfs_itruncate_extents.xfs_free_eofblocks.xfs_release.xfs_file_release.__fput.____fput.task_work_run
2006 ± 25% 3e+04 31143 ± 35%
latency_stats.sum.call_rwsem_down_read_failed.xfs_log_commit_cil.__xfs_trans_commit.__xfs_trans_roll.xfs_trans_roll.xfs_itruncate_extents.xfs_inactive_truncate.xfs_inactive.xfs_fs_destroy_inode.destroy_inode.evict.iput
29 ±101% 1e+04 10214 ± 29%
latency_stats.sum.call_rwsem_down_read_failed.xfs_log_commit_cil.__xfs_trans_commit.__xfs_trans_roll.xfs_trans_roll.xfs_defer_trans_roll.xfs_defer_finish.xfs_itruncate_extents.xfs_inactive_truncate.xfs_inactive.xfs_fs_destroy_inode.destroy_inode
1206 ± 51% 9e+03 9919 ± 25%
latency_stats.sum.call_rwsem_down_read_failed.xfs_log_commit_cil.__xfs_trans_commit.xfs_trans_commit.xfs_vn_update_time.touch_atime.generic_file_read_iter.xfs_file_buffered_aio_read.xfs_file_read_iter.__vfs_read.vfs_read.SyS_read
Significant increase in blocking delays in the journal during atime
updates. There's nothing in Christoph's tree that would affect that
behaviour. This smells like either a mount option change or
individual tests not being 100% isolated and the previous test run
is affecting this one?
We kexec reboot machines between tests to make sure zero influence
from previous test. The test jobs are queued in a batch and not
likely to change mount option etc. in between (just confirmed).
The kernels are build by a random build server and some builds will
reuse previous .o files (no distclean). To make sure I rebuilt the
kernels in the same build server with distclean. However new tests
still show the same numbers.
Thanks,
Fengguang