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From: Feng Tang <feng.tang@intel.com>
To: Andi Kleen <ak@linux.intel.com>
Cc: Michal Koutn?? <mkoutny@suse.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	andi.kleen@intel.com, kernel test robot <oliver.sang@intel.com>,
	Roman Gushchin <guro@fb.com>, Michal Hocko <mhocko@suse.com>,
	Shakeel Butt <shakeelb@google.com>,
	Balbir Singh <bsingharora@gmail.com>, Tejun Heo <tj@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	lkp@lists.01.org, kernel test robot <lkp@intel.com>,
	"Huang, Ying" <ying.huang@intel.com>,
	Zhengjun Xing <zhengjun.xing@linux.intel.com>
Subject: Re: [mm] 2d146aa3aa: vm-scalability.throughput -36.4% regression
Date: Thu, 2 Sep 2021 11:46:28 +0800	[thread overview]
Message-ID: <20210902034628.GA76472@shbuild999.sh.intel.com> (raw)
In-Reply-To: <e8d087a4-a286-3561-66ef-1e9cfb38605f@linux.intel.com>

On Wed, Sep 01, 2021 at 07:23:24PM -0700, Andi Kleen wrote:
> 
> On 9/1/2021 6:35 PM, Feng Tang wrote:
> >On Wed, Sep 01, 2021 at 08:12:24AM -0700, Andi Kleen wrote:
> >>Feng Tang <feng.tang@intel.com> writes:
> >>>Yes, the tests I did is no matter where the 128B padding is added, the
> >>>performance can be restored and even improved.
> >>I wonder if we can find some cold, rarely accessed, data to put into the
> >>padding to not waste it. Perhaps some name strings? Or the destroy
> >>support, which doesn't sound like its commonly used.
> >Yes, I tried to move 'destroy_work', 'destroy_rwork' and 'parent' over
> >before the 'refcnt' together with some padding, it restored the performance
> >to about 10~15% regression. (debug patch pasted below)
> >
> >But I'm not sure if we should use it, before we can fully explain the
> >regression.
> 
> Narrowing it down to a single prefetcher seems good enough to me. The
> behavior of the prefetchers is fairly complicated and hard to predict, so I
> doubt you'll ever get a 100% step by step explanation.

Yes, I'm afriad so, given that the policy/algorithm used by perfetcher
keeps changing from generation to generation.

I will test the patch more with other benchmarks.

Thanks,
Feng

> 
> -Andi
> 

  reply	other threads:[~2021-09-02  3:46 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-11  3:17 [mm] 2d146aa3aa: vm-scalability.throughput -36.4% regression kernel test robot
2021-08-11  5:59 ` Linus Torvalds
2021-08-11 20:12   ` Johannes Weiner
2021-08-12  3:19   ` Feng Tang
2021-08-16  3:28     ` Feng Tang
2021-08-16 21:41       ` Johannes Weiner
2021-08-17  2:45         ` Feng Tang
2021-08-17 16:47           ` Michal Koutný
2021-08-17 17:10             ` Shakeel Butt
2021-08-18  2:30             ` Feng Tang
2021-08-30 14:51               ` Michal Koutný
2021-08-31  6:30                 ` Feng Tang
2021-08-31  9:23                   ` Michal Koutný
2021-09-01  4:50                     ` Feng Tang
2021-09-01 15:12                       ` Andi Kleen
2021-09-02  1:35                         ` Feng Tang
2021-09-02  2:23                           ` Andi Kleen
2021-09-02  3:46                             ` Feng Tang [this message]
2021-09-02 10:53                               ` Michal Koutný
2021-09-02 13:39                                 ` Feng Tang

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