linux-kernel - Re: [mm/page_alloc] f26b3fa046: netperf.Throughput

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Message-ID: <41c08a5371957acac5310a2e608b2e42bd231558.camel@intel.com>
Date:   Wed, 11 May 2022 09:58:23 +0800
From:   "ying.huang@...el.com" <ying.huang@...el.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Waiman Long <longman@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>
Cc:     Aaron Lu <aaron.lu@...el.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        kernel test robot <oliver.sang@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        kernel test robot <lkp@...el.com>,
        Feng Tang <feng.tang@...el.com>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        fengwei.yin@...el.com
Subject: Re: [mm/page_alloc] f26b3fa046: netperf.Throughput_Mbps -18.0%
 regression

On Tue, 2022-05-10 at 11:05 -0700, Linus Torvalds wrote:
> [ Adding locking people in case they have any input ]
> 
> On Mon, May 9, 2022 at 11:23 PM ying.huang@...el.com
> <ying.huang@...el.com> wrote:
> > 
> > > 
> > > Can you point me to the regression report? I would like to take a look,
> > > thanks.
> > 
> > https://lore.kernel.org/all/1425108604.10337.84.camel@linux.intel.com/
> 
> Hmm.
> 
> That explanation looks believable, except that our qspinlocks
> shouldn't be spinning on the lock itself, but spinning on the mcs node
> it inserts into the lock.

The referenced regression report is very old (in Feb 2015 for 3.16-
3.17).  The ticket spinlock was still used at that time.  I believe that
things become much better after we used qspinlock.  We can test that.

Best Regards,
Huang, Ying