Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <41c08a5371957acac5310a2e608b2e42bd231558.camel@intel.com>
Subject: Re: [mm/page_alloc] f26b3fa046: netperf.Throughput_Mbps -18.0%
 regression
From:   "ying.huang@intel.com" <ying.huang@intel.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>,
        Waiman Long <longman@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Will Deacon <will@kernel.org>
Cc:     Aaron Lu <aaron.lu@intel.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        kernel test robot <oliver.sang@intel.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
        Michal Hocko <mhocko@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>, lkp@lists.01.org,
        kernel test robot <lkp@intel.com>,
        Feng Tang <feng.tang@intel.com>,
        Zhengjun Xing <zhengjun.xing@linux.intel.com>,
        fengwei.yin@intel.com
Date:   Wed, 11 May 2022 09:58:23 +0800
In-Reply-To: <CAHk-=wjguW5nxjagV99GHvc_-E_7mSg+LMvGtFjJ9LUSx4Skig@mail.gmail.com>
References: <20220420013526.GB14333@xsang-OptiPlex-9020>
         <YmvMDyx05UoPFtQy@ziqianlu-desk1>
         <bd3db4de223a010d1e06013e93b09879fc9b36a8.camel@intel.com>
         <YnURx04+hE0sQ3v3@ziqianlu-desk1>
         <7d20a9543f69523cfda280e3f5ab17d68db037ab.camel@intel.com>
         <YnXnLuYjmEWdVyBP@ziqianlu-desk1>
         <ae763d63e50d14650c5762103d113934412bef57.camel@intel.com>
         <ba83270a-4f37-7d5a-b37a-0b7a6df5f5b4@intel.com>
         <d13688d1483e9d87ec477292893f2916832b3bdc.camel@intel.com>
         <c11ae803-cea7-8b7f-9992-2f640c90f104@intel.com>
         <37dac785a08e3a341bf05d9ee35f19718ce83d26.camel@intel.com>
         <CAHk-=wjguW5nxjagV99GHvc_-E_7mSg+LMvGtFjJ9LUSx4Skig@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
User-Agent: Evolution 3.38.3-1 
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Precedence: bulk

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@intel.com
> <ying.huang@intel.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