On Tue, Jun 05, 2018 at 03:16:57PM +0800, kernel test robot wrote:
>
> Greeting,
>
> FYI, we noticed a +7.1%% regression of fio.latency_2ms% due to commit:
>
>
> commit: b027d4c97b9675c2ad75dec94be4e46dceb3ec74 ("xfs: don't retry xfs_buf_find on XBF_TRYLOCK failure")
> https://git.kernel.org/cgit/fs/xfs/xfs-linux.git xfs-4.18-merge
....
> 8925a3dc4771004b b027d4c97b9675c2ad75dec94b
> ---------------- --------------------------
> %stddev %change %stddev
> \ | \
> 46.56 ± 3% +7.1 53.61 fio.latency_2ms%
> 8.19 +0.2 8.40 fio.latency_100ms%
> 0.74 ± 3% -0.1 0.68 ± 6% fio.latency_250ms%
> 25.20 ± 6% -7.3 17.86 ± 6% fio.latency_4ms%
> 0.46 ± 9% +0.2 0.69 ± 13% fio.latency_750us%
This is not a regression. The number of IOs in the 4ms IO latency
bin has reduced by 7%, and inumber in the 2ms IO latency bin has
increased by 7%. IOWs, there's a measurable improvement in IO
latency as a result of those patches, not a regression.
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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