Re: [LKP] [lkp-robot] [mm] 9092c71bb7: blogbench.write_score -12.3% regression

["Huang\, Ying" <ying.huang@intel.com>]

Chris Mason <clm@fb.com> writes:

> On 19 Jun 2018, at 23:51, Huang, Ying wrote:
>>>> "Huang, Ying" <ying.huang@intel.com> writes:
>>>>
>>>>> Hi, Josef,
>>>>>
>>>>> Do you have time to take a look at the regression?
>>>>>
>>>>> kernel test robot <xiaolong.ye@intel.com> writes:
>>>>>
>>>>>> Greeting,
>>>>>>
>>>>>> FYI, we noticed a -12.3% regression of blogbench.write_score and
>>>>>> a +9.6% improvement
>>>>>> of blogbench.read_score due to commit:
>>>>>>
>>>>>>
>>>>>> commit: 9092c71bb724dba2ecba849eae69e5c9d39bd3d2 ("mm: use
>>>>>> sc->priority for slab shrink targets")
>>>>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git
>>>>>> master
>>>>>>
>>>>>> in testcase: blogbench
>>>>>> on test machine: 16 threads Intel(R) Xeon(R) CPU D-1541 @
>>>>>> 2.10GHz with 8G memory
>>>>>> with following parameters:
>>>>>>
>>>>>> 	disk: 1SSD
>>>>>> 	fs: btrfs
>>>>>> 	cpufreq_governor: performance
>>>>>>
>>>>>> test-description: Blogbench is a portable filesystem benchmark
>>>>>> that tries to reproduce the load of a real-world busy file
>>>>>> server.
>>>>>> test-url:
>
> I'm surprised, this patch is a big win in production here at FB.  I'll
> have to reproduce these results to better understand what is going on.
> My first guess is that since we have fewer inodes in slab, we're
> reading more inodes from disk in order to do the writes.
>
> But that should also make our read scores lower.

Thanks for looking at this.  If you need more information, please let me
know.

Best Regards,
Huang, Ying