Re: [percpu_ref] 2b0d3d3e4f: reaim.jobs_per_min -18.4% regression

[Xing, Zhengjun <zhengjun.xing@intel.com>]

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On 1/11/2021 5:58 PM, Ming Lei wrote:
> On Sun, Jan 10, 2021 at 10:32:47PM +0800, kernel test robot wrote:
>> Greeting,
>>
>> FYI, we noticed a -18.4% regression of reaim.jobs_per_min due to commit:
>>
>>
>> commit: 2b0d3d3e4fcfb19d10f9a82910b8f0f05c56ee3e ("percpu_ref: reduce memory footprint of percpu_ref in fast path")
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
>>
>>
>> in testcase: reaim
>> on test machine: 192 threads Intel(R) Xeon(R) Platinum 9242 CPU @ 2.30GHz with 192G memory
>> with following parameters:
>>
>> 	runtime: 300s
>> 	nr_task: 100%
>> 	test: short
>> 	cpufreq_governor: performance
>> 	ucode: 0x5002f01
>>
>> test-description: REAIM is an updated and improved version of AIM 7 benchmark.
>> test-url: https://sourceforge.net/projects/re-aim-7/
>>
>> In addition to that, the commit also has significant impact on the following tests:
>>
>> +------------------+---------------------------------------------------------------------------+
>> | testcase: change | vm-scalability: vm-scalability.throughput -2.8% regression                |
>> | test machine     | 192 threads Intel(R) Xeon(R) Platinum 9242 CPU @ 2.30GHz with 192G memory |
>> | test parameters  | cpufreq_governor=performance                                              |
>> |                  | runtime=300s                                                              |
>> |                  | test=lru-file-mmap-read-rand                                              |
>> |                  | ucode=0x5003003                                                           |
>> +------------------+---------------------------------------------------------------------------+
>> | testcase: change | will-it-scale: will-it-scale.per_process_ops 14.5% improvement            |
>> | test machine     | 144 threads Intel(R) Xeon(R) CPU E7-8890 v3 @ 2.50GHz with 512G memory    |
>> | test parameters  | cpufreq_governor=performance                                              |
>> |                  | mode=process                                                              |
>> |                  | nr_task=50%                                                               |
>> |                  | test=page_fault2                                                          |
>> |                  | ucode=0x16                                                                |
>> +------------------+---------------------------------------------------------------------------+
>> | testcase: change | will-it-scale: will-it-scale.per_process_ops -13.0% regression            |
>> | test machine     | 104 threads Skylake with 192G memory                                      |
>> | test parameters  | cpufreq_governor=performance                                              |
>> |                  | mode=process                                                              |
>> |                  | nr_task=50%                                                               |
>> |                  | test=malloc1                                                              |
>> |                  | ucode=0x2006906                                                           |
>> +------------------+---------------------------------------------------------------------------+
>> | testcase: change | vm-scalability: vm-scalability.throughput -2.3% regression                |
>> | test machine     | 96 threads Intel(R) Xeon(R) CPU @ 2.30GHz with 128G memory                |
>> | test parameters  | cpufreq_governor=performance                                              |
>> |                  | runtime=300s                                                              |
>> |                  | test=lru-file-mmap-read-rand                                              |
>> |                  | ucode=0x5002f01                                                           |
>> +------------------+---------------------------------------------------------------------------+
>> | testcase: change | fio-basic: fio.read_iops -4.8% regression                                 |
>> | test machine     | 192 threads Intel(R) Xeon(R) Platinum 9242 CPU @ 2.30GHz with 192G memory |
>> | test parameters  | bs=4k                                                                     |
>> |                  | cpufreq_governor=performance                                              |
>> |                  | disk=2pmem                                                                |
>> |                  | fs=xfs                                                                    |
>> |                  | ioengine=libaio                                                           |
>> |                  | nr_task=50%                                                               |
>> |                  | runtime=200s                                                              |
>> |                  | rw=randread                                                               |
>> |                  | test_size=200G                                                            |
>> |                  | time_based=tb                                                             |
>> |                  | ucode=0x5002f01                                                           |
>> +------------------+---------------------------------------------------------------------------+
>> | testcase: change | stress-ng: stress-ng.stackmmap.ops_per_sec -45.4% regression              |
>> | test machine     | 96 threads Intel(R) Xeon(R) Gold 6252 CPU @ 2.10GHz with 256G memory      |
>> | test parameters  | class=memory                                                              |
>> |                  | cpufreq_governor=performance                                              |
>> |                  | disk=1HDD                                                                 |
>> |                  | nr_threads=100%                                                           |
>> |                  | testtime=10s                                                              |
>> |                  | ucode=0x5002f01                                                           |
>> +------------------+---------------------------------------------------------------------------+
> Just run a quick test of the last two on 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of
> percpu_ref in fast path) and cf785af19319 ("block: warn if !__GFP_DIRECT_RECLAIM in bio_crypt_set_ctx()").
>
> Not see difference in the two kernel(fio on null_blk with 224 hw queues,
> and 'stress-ng --stackmmap-ops') on one 224 cores, dual sockets system.
>
> BTW this patch itself doesn't touch fast path code, so it is supposed to
> not affect performance.
>
> Can you double check if the test itself is good?
I re-test the "fio-basic: fio.read_iops -4.8% regression"  for more than 
5 times, the average regression is -2.3%.
For "stress_ng", normally, it tests a lot of cases one by one. Command  
'stress-ng --stackmmap-ops' only test  "stackmmap" case.
I also tried only test "stackmmap" case, the regression is -7.8%.

But for here, it mainly reports "reaim.jobs_per_min -18.4% regression", 
I re-test  "reaim" case, the result is almost the same.
>
> Note: cf785af19319 is 2b0d3d3e4fcf^
>
>
>
> Thanks,
> Ming
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-- 
Zhengjun Xing