Messages in this thread |  | | Date | Tue, 7 Jan 2020 11:57:08 -0500 | From | "Theodore Y. Ts'o" <> | Subject | Re: [ext4] b1b4705d54: filebench.sum_bytes_mb/s -20.2% regression |
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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.
Yeah, it's confusing. I believe Dave Chinner has complianed about this previously.
- Ted
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