Messages in this thread |  | | Date | Tue, 7 Jan 2020 18:28:24 +0100 | From | Jan Kara <> | Subject | Re: [ext4] b1b4705d54: filebench.sum_bytes_mb/s -20.2% regression |
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On Tue 07-01-20 11:57:08, Theodore Y. Ts'o wrote: > On Tue, Jan 07, 2020 at 02:41:06PM +0100, Jan Kara wrote: > > Hello, > > > > On Tue 24-12-19 08:59:15, kernel test robot wrote: > > > FYI, we noticed a -20.2% regression of filebench.sum_bytes_mb/s due to commit: > > > > > > > > > commit: b1b4705d54abedfd69dcdf42779c521aa1e0fbd3 ("ext4: introduce direct I/O read using iomap infrastructure") > > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master > > > > > > in testcase: filebench > > > on test machine: 8 threads Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz with 8G memory > > > with following parameters: > > > > > > disk: 1HDD > > > fs: ext4 > > > test: fivestreamreaddirect.f > > > cpufreq_governor: performance > > > ucode: 0x27 > > > > I was trying to reproduce this but I failed with my test VM. I had SATA SSD > > as a backing store though so maybe that's what makes a difference. Maybe > > the new code results in somewhat more seeks because the five threads which > > compete in submitting sequential IO end up being more interleaved? > > A "-20.2% regression" should be read as a "20.2% performance > improvement" is zero-day kernel speak.
Are you sure? I can see:
58.30 ± 2% -20.2% 46.53 filebench.sum_bytes_mb/s
which implies to me previously the throughput was 58 MB/s and after the commit it was 46 MB/s?
Anyway, in my testing that commit made no difference in that benchmark whasoever (getting around 97 MB/s for each thread before and after the commit).
Honza -- Jan Kara <jack@suse.com> SUSE Labs, CR
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