From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id AC3CE6B02F4 for ; Tue, 25 Jul 2017 11:07:26 -0400 (EDT) Received: by mail-pg0-f70.google.com with SMTP id q15so13774947pgc.3 for ; Tue, 25 Jul 2017 08:07:26 -0700 (PDT) Received: from mail-pg0-x244.google.com (mail-pg0-x244.google.com. [2607:f8b0:400e:c05::244]) by mx.google.com with ESMTPS id r19si8330267pgj.246.2017.07.25.08.07.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 25 Jul 2017 08:07:25 -0700 (PDT) Received: by mail-pg0-x244.google.com with SMTP id g14so10076819pgu.4 for ; Tue, 25 Jul 2017 08:07:25 -0700 (PDT) Date: Tue, 25 Jul 2017 18:07:19 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Message-ID: <20170725150719.74j7fbfzagrn7olb@node.shutemov.name> References: <20170724072332.31903-1-mhocko@kernel.org> <20170724140008.sd2n6af6izjyjtda@node.shutemov.name> <20170724141526.GM25221@dhcp22.suse.cz> <20170724145142.i5xqpie3joyxbnck@node.shutemov.name> <20170724161146.GQ25221@dhcp22.suse.cz> <20170725141723.ivukwhddk2voyhuc@node.shutemov.name> <20170725142617.GI26723@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170725142617.GI26723@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , David Rientjes , Tetsuo Handa , Oleg Nesterov , Hugh Dickins , Andrea Arcangeli , linux-mm@kvack.org, LKML On Tue, Jul 25, 2017 at 04:26:17PM +0200, Michal Hocko wrote: > On Tue 25-07-17 17:17:23, Kirill A. Shutemov wrote: > [...] > > Below are numbers for the same test case, but from bigger machine (48 > > threads, 64GiB of RAM). > > > > v4.13-rc2: > > > > Performance counter stats for './a.sh 100000' (5 runs): > > > > 159857.233790 task-clock:u (msec) # 1.000 CPUs utilized ( +- 3.21% ) > > 0 context-switches:u # 0.000 K/sec > > 0 cpu-migrations:u # 0.000 K/sec > > 8,761,843 page-faults:u # 0.055 M/sec ( +- 0.64% ) > > 38,725,763,026 cycles:u # 0.242 GHz ( +- 0.18% ) > > 272,691,643,016 stalled-cycles-frontend:u # 704.16% frontend cycles idle ( +- 3.16% ) > > 22,221,416,575 instructions:u # 0.57 insn per cycle > > # 12.27 stalled cycles per insn ( +- 0.00% ) > > 5,306,829,649 branches:u # 33.197 M/sec ( +- 0.00% ) > > 240,783,599 branch-misses:u # 4.54% of all branches ( +- 0.15% ) > > > > 159.808721098 seconds time elapsed ( +- 3.15% ) > > > > v4.13-rc2 + the patch: > > > > Performance counter stats for './a.sh 100000' (5 runs): > > > > 167628.094556 task-clock:u (msec) # 1.007 CPUs utilized ( +- 1.63% ) > > 0 context-switches:u # 0.000 K/sec > > 0 cpu-migrations:u # 0.000 K/sec > > 8,838,314 page-faults:u # 0.053 M/sec ( +- 0.26% ) > > 38,862,240,137 cycles:u # 0.232 GHz ( +- 0.10% ) > > 282,105,057,553 stalled-cycles-frontend:u # 725.91% frontend cycles idle ( +- 1.64% ) > > 22,219,273,623 instructions:u # 0.57 insn per cycle > > # 12.70 stalled cycles per insn ( +- 0.00% ) > > 5,306,165,194 branches:u # 31.654 M/sec ( +- 0.00% ) > > 240,473,075 branch-misses:u # 4.53% of all branches ( +- 0.07% ) > > > > 166.497005412 seconds time elapsed ( +- 1.61% ) > > > > IMO, there is something to think about. ~4% slowdown is not insignificant. > > I expect effect to be bigger for larger machines. > > Thanks for retesting Kirill. Are those numbers stable over runs? E.g. > the run without the patch has ~3% variance while the one with the patch > has it smaller. This sounds suspicious to me. There shouldn't be any > lock contention (except for the oom killer) so the lock shouldn't make > any difference wrt. variability. There's run-to-tun variability. I'll post new numbers for your new test. -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org