linux-kernel - Re: [PATCH v2] kernel: release ptraced tasks before zap_pid_ns

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Date:   Wed, 27 Feb 2019 09:03:35 +0100
From:   Jiri Slaby <jslaby@...e.cz>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Andrei Vagin <avagin@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH v2] kernel: release ptraced tasks before
 zap_pid_ns_processes

On 26. 02. 19, 16:30, Oleg Nesterov wrote:
>> from our (SUSE) QA we received a report that this patch causes a
>> performance decline in libmicro pthread_* benchmark as reported in:
>> https://bugzilla.suse.com/show_bug.cgi?id=1126762
> 
> Access Denied
> 
>> I tried myself from the repo:
>> https://github.com/redhat-performance/libMicro
>>
>> I ran
>> pthread_create -B 8 -C 200 -S
>>
>> and with the patch applied:
>> # STATISTICS       usecs/call (raw)          usecs/call (outliers removed)
>> #                   mean     23.38611                17.29311
>>
>> Without:
>> #                   mean     41.36539                39.21347
> 
> can't reproduce, I see the same numbers with or without this patch.
> However, I did "./bin/pthread_create -B 8 -C 200 -S" under KVM.

Correct. I did the tests also under KVM. The above difference happens
when you compare (by stupid mistake) a LOCKDEP and non-LOCKDEP kernel --
sorry. So the proper results are comparably the same -- the difference
is on the noise level. So it must be their setup broken too.

Thanks for the input anyway.

-- 
js
suse labs