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From: Feng Tang <feng.tang@intel.com>
To: lkp@lists.01.org
Subject: Re: [perf/x86] 81ec3f3c4c: will-it-scale.per_process_ops -5.5% regression
Date: Mon, 24 Feb 2020 21:20:14 +0800	[thread overview]
Message-ID: <20200224132014.GA63607@shbuild999.sh.intel.com> (raw)
In-Reply-To: <20200224021915.GC5061@shbuild999.sh.intel.com>

[-- Attachment #1: Type: text/plain, Size: 867 bytes --]

On Mon, Feb 24, 2020 at 10:19:15AM +0800, Feng Tang wrote:
> > 
> > > No, it's not the biggest, I tried another machine 'Xeon Phi(TM) CPU 7295',
> > > which has 72C/288T, and the regression is not seen. This is the part
> > > confusing me :)
> > 
> > Hmm.
> > 
> > Humor me - what  happens if you turn off SMT on that Cascade Lake
> > system?  Maybe it's about the thread ID bit in the L1? Although again,
> > I'd have expected things to get _worse_ if it's the two fields that
> > are now in the same cachline thanks to alignment.
> 
> I'll try it and report back.

I added "nosmt=force" on the 2S 4 nodes 96C/192T machine, and tested
both 96 and 192 processes, and the regression still exists.

Also for Ying's suggestion about separate 'sigpending' to another cache
line than '__refcount', it can not heal the regression either.

Thanks,
Feng

WARNING: multiple messages have this Message-ID (diff)
From: Feng Tang <feng.tang@intel.com>
To: Linus Torvalds <torvalds@linux-foundation.org>, ying.huang@intel.com
Cc: Jiri Olsa <jolsa@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	kernel test robot <rong.a.chen@intel.com>,
	Ingo Molnar <mingo@kernel.org>,
	Vince Weaver <vincent.weaver@maine.edu>,
	Jiri Olsa <jolsa@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Arnaldo Carvalho de Melo <acme@redhat.com>,
	"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
	Ravi Bangoria <ravi.bangoria@linux.ibm.com>,
	Stephane Eranian <eranian@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>,
	lkp@lists.01.org, andi.kleen@intel.com, "Huang,
	Ying" <ying.huang@intel.com>
Subject: Re: [LKP] Re: [perf/x86] 81ec3f3c4c: will-it-scale.per_process_ops -5.5% regression
Date: Mon, 24 Feb 2020 21:20:14 +0800	[thread overview]
Message-ID: <20200224132014.GA63607@shbuild999.sh.intel.com> (raw)
In-Reply-To: <20200224021915.GC5061@shbuild999.sh.intel.com>

On Mon, Feb 24, 2020 at 10:19:15AM +0800, Feng Tang wrote:
> > 
> > > No, it's not the biggest, I tried another machine 'Xeon Phi(TM) CPU 7295',
> > > which has 72C/288T, and the regression is not seen. This is the part
> > > confusing me :)
> > 
> > Hmm.
> > 
> > Humor me - what  happens if you turn off SMT on that Cascade Lake
> > system?  Maybe it's about the thread ID bit in the L1? Although again,
> > I'd have expected things to get _worse_ if it's the two fields that
> > are now in the same cachline thanks to alignment.
> 
> I'll try it and report back.

I added "nosmt=force" on the 2S 4 nodes 96C/192T machine, and tested
both 96 and 192 processes, and the regression still exists.

Also for Ying's suggestion about separate 'sigpending' to another cache
line than '__refcount', it can not heal the regression either.

Thanks,
Feng

  reply	other threads:[~2020-02-24 13:20 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-05 12:32 [perf/x86] 81ec3f3c4c: will-it-scale.per_process_ops -5.5% regression kernel test robot
2020-02-05 12:32 ` kernel test robot
2020-02-05 12:58 ` Peter Zijlstra
2020-02-05 12:58   ` Peter Zijlstra
2020-02-06  3:04   ` Li, Philip
2020-02-06  3:04     ` [LKP] " Li, Philip
2020-02-21  8:03   ` Feng Tang
2020-02-21  8:03     ` [LKP] " Feng Tang
2020-02-21 10:58     ` Peter Zijlstra
2020-02-21 10:58       ` [LKP] " Peter Zijlstra
2020-02-21 13:20     ` Jiri Olsa
2020-02-21 13:20       ` [LKP] " Jiri Olsa
2020-02-23 14:11       ` Feng Tang
2020-02-23 14:11         ` [LKP] " Feng Tang
2020-02-23 17:37         ` Linus Torvalds
2020-02-23 17:37           ` [LKP] " Linus Torvalds
2020-02-24  0:33           ` Feng Tang
2020-02-24  0:33             ` [LKP] " Feng Tang
2020-02-24  1:06             ` Linus Torvalds
2020-02-24  1:06               ` [LKP] " Linus Torvalds
2020-02-24  1:58               ` Huang, Ying
2020-02-24  1:58                 ` [LKP] " Huang, Ying
2020-02-24  2:19               ` Feng Tang
2020-02-24  2:19                 ` [LKP] " Feng Tang
2020-02-24 13:20                 ` Feng Tang [this message]
2020-02-24 13:20                   ` Feng Tang
2020-02-24 19:24                 ` Linus Torvalds
2020-02-24 19:24                   ` [LKP] " Linus Torvalds
2020-02-24 19:42                   ` Kleen, Andi
2020-02-24 19:42                     ` [LKP] " Kleen, Andi
2020-02-24 20:09                   ` Linus Torvalds
2020-02-24 20:09                     ` [LKP] " Linus Torvalds
2020-02-24 20:47                     ` Linus Torvalds
2020-02-24 20:47                       ` [LKP] " Linus Torvalds
2020-02-24 21:20                       ` Eric W. Biederman
2020-02-24 21:20                         ` [LKP] " Eric W. Biederman
2020-02-24 21:43                         ` Linus Torvalds
2020-02-24 21:43                           ` [LKP] " Linus Torvalds
2020-02-24 21:59                           ` Eric W. Biederman
2020-02-24 21:59                             ` [LKP] " Eric W. Biederman
2020-02-24 22:12                             ` Linus Torvalds
2020-02-24 22:12                               ` [LKP] " Linus Torvalds
2020-02-25  2:57                       ` Feng Tang
2020-02-25  2:57                         ` [LKP] " Feng Tang
2020-02-25  3:15                         ` Linus Torvalds
2020-02-25  3:15                           ` [LKP] " Linus Torvalds
2020-02-25  4:53                           ` Feng Tang
2020-02-25  4:53                             ` [LKP] " Feng Tang
2020-02-23 19:36         ` Jiri Olsa
2020-02-23 19:36           ` [LKP] " Jiri Olsa
2020-02-24  1:14           ` Feng Tang
2020-02-21 18:05     ` Kleen, Andi
2020-02-21 18:05       ` [LKP] " Kleen, Andi
2020-02-22 12:43       ` Feng Tang
2020-02-22 12:43         ` [LKP] " Feng Tang
2020-02-22 17:08         ` Kleen, Andi
2020-02-22 17:08           ` [LKP] " Kleen, Andi

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