Messages in this thread |  | | Subject | Re: [ext4] b1b4705d54: filebench.sum_bytes_mb/s -20.2% regression | From | Rong Chen <> | Date | Wed, 8 Jan 2020 10:31:35 +0800 |
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On 1/8/20 1:28 AM, Jan Kara wrote: > 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
We're sorry for the misunderstanding, "-20.2%" means the change of filebench.sum_bytes_mb/s, "regression" means the explanation of this change from LKP.
Best Regards, Rong Chen
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