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From: ebiederm@xmission.com (Eric W. Biederman)
To: Alexey Gladkov <gladkov.alexey@gmail.com>
Cc: kernel test robot <oliver.sang@intel.com>,
	 0day robot <lkp@intel.com>,  LKML <linux-kernel@vger.kernel.org>,
	 lkp@lists.01.org,  ying.huang@intel.com,  feng.tang@intel.com,
	 zhengjun.xing@intel.com,  io-uring@vger.kernel.org,
	 Kernel Hardening <kernel-hardening@lists.openwall.com>,
	 Linux Containers <containers@lists.linux-foundation.org>,
	 linux-mm@kvack.org,  Andrew Morton <akpm@linux-foundation.org>,
	 Christian Brauner <christian.brauner@ubuntu.com>,
	 Jann Horn <jannh@google.com>,  Jens Axboe <axboe@kernel.dk>,
	 Kees Cook <keescook@chromium.org>,
	 Linus Torvalds <torvalds@linux-foundation.org>,
	 Oleg Nesterov <oleg@redhat.com>
Subject: Re: d28296d248:  stress-ng.sigsegv.ops_per_sec -82.7% regression
Date: Wed, 24 Feb 2021 12:50:21 -0600	[thread overview]
Message-ID: <m17dmxl2qa.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <20210224183828.j6uut6sholeo2fzh@example.org> (Alexey Gladkov's message of "Wed, 24 Feb 2021 19:38:28 +0100")

Alexey Gladkov <gladkov.alexey@gmail.com> writes:

> On Wed, Feb 24, 2021 at 10:54:17AM -0600, Eric W. Biederman wrote:
>> kernel test robot <oliver.sang@intel.com> writes:
>> 
>> > Greeting,
>> >
>> > FYI, we noticed a -82.7% regression of stress-ng.sigsegv.ops_per_sec due to commit:
>> >
>> >
>> > commit: d28296d2484fa11e94dff65e93eb25802a443d47 ("[PATCH v7 5/7] Reimplement RLIMIT_SIGPENDING on top of ucounts")
>> > url: https://github.com/0day-ci/linux/commits/Alexey-Gladkov/Count-rlimits-in-each-user-namespace/20210222-175836
>> > base: https://git.kernel.org/cgit/linux/kernel/git/shuah/linux-kselftest.git next
>> >
>> > in testcase: stress-ng
>> > on test machine: 48 threads Intel(R) Xeon(R) CPU E5-2697 v2 @ 2.70GHz with 112G memory
>> > with following parameters:
>> >
>> > 	nr_threads: 100%
>> > 	disk: 1HDD
>> > 	testtime: 60s
>> > 	class: interrupt
>> > 	test: sigsegv
>> > 	cpufreq_governor: performance
>> > 	ucode: 0x42e
>> >
>> >
>> > In addition to that, the commit also has significant impact on the
>> > following tests:
>> 
>> Thank you.  Now we have a sense of where we need to test the performance
>> of these changes carefully.
>
> One of the reasons for this is that I rolled back the patch that changed
> the ucounts.count type to atomic_t. Now get_ucounts() is forced to use a
> spin_lock to increase the reference count.

Which given the hickups with getting a working version seems justified.

Now we can add incremental patches on top to improve the performance.


Eric



  reply	other threads:[~2021-02-24 18:50 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-22  9:56 [PATCH v7 0/7] Count rlimits in each user namespace Alexey Gladkov
2021-02-22  9:56 ` [PATCH v7 1/7] Increase size of ucounts to atomic_long_t Alexey Gladkov
2021-02-22  9:56 ` [PATCH v7 2/7] Add a reference to ucounts for each cred Alexey Gladkov
2021-03-01  7:32   ` e1e57d56fe: stress-ng.access.ops_per_sec -41.6% regression kernel test robot
2021-02-22  9:56 ` [PATCH v7 3/7] Reimplement RLIMIT_NPROC on top of ucounts Alexey Gladkov
2021-02-22  9:56 ` [PATCH v7 4/7] Reimplement RLIMIT_MSGQUEUE " Alexey Gladkov
2021-02-22  9:56 ` [PATCH v7 5/7] Reimplement RLIMIT_SIGPENDING " Alexey Gladkov
2021-02-24  5:18   ` d28296d248: stress-ng.sigsegv.ops_per_sec -82.7% regression kernel test robot
2021-02-24 16:54     ` Eric W. Biederman
2021-02-24 18:38       ` Alexey Gladkov
2021-02-24 18:50         ` Eric W. Biederman [this message]
2021-02-25 20:36           ` Alexey Gladkov
2021-03-05 17:56             ` Eric W. Biederman
2021-02-24 19:10         ` Linus Torvalds
2021-02-22  9:56 ` [PATCH v7 6/7] Reimplement RLIMIT_MEMLOCK on top of ucounts Alexey Gladkov
2021-03-01  6:51   ` 5b5c35b757: BUG:KASAN:use-after-free_in_dec_rlimit_ucounts kernel test robot
2021-02-22  9:56 ` [PATCH v7 7/7] kselftests: Add test to check for rlimit changes in different user namespaces Alexey Gladkov

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