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b=RG8Yk8CoQJzkrKneL6NEZL3q0bJ6BABh1zXM4L85UnjG6Mhsmc9q5a332GcI/0/+c Sy0DFF2buPwibDz5RtUKRT4JKsz3vMOWhOc2AR7q/cWuoA/wq9tQkDZN1U0VcZi4md Oel3fPwbXDrTFifXG9MKy+iRagvUFjcS7jDwjSDk= Date: Sat, 12 Oct 2024 15:43:28 -0700 From: Andrew Morton To: alexjlzheng@gmail.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, alexjlzheng@tencent.com, MengEn Sun Subject: Re: [PATCH] mm: make pcp decay work with onhz Message-Id: <20241012154328.015f57635566485ad60712f3@linux-foundation.org> In-Reply-To: <20241011103609.1992042-1-mengensun@tencent.com> References: <20241011103609.1992042-1-mengensun@tencent.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 76AE74000B X-Stat-Signature: ieyk1jqn918o51sm1nikiqq9zmyoy3ho X-HE-Tag: 1728773006-356572 X-HE-Meta: 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 WwC+fnAL PxB1g7frUUD0ngqALGZ+1AVRxV4xxqJwfh9a713rKmmWsugCAnqBmhYAkqy4UM2xKU3wH0UUxKRxgFPMYhJ5/zgdyeV5aQwCf48OIzukxmzdOEMwziBcZjItskJBOf9YUBd9KeR/Xf/RjpkAwoLvKdNqEW59wqGZFgEH4jaNPhKWUYZoJYPPyIShiVK80hxck2h4aAFZ7SmWct7CEGLeThQik7nLCLHxE24eAqaKyVsgpBoU3ws/QtoZCviyghqCGjHfBJmuESI8waJd+FX00j2ptDwI70IPOouXg213esuG5/QA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000040, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 11 Oct 2024 18:36:10 +0800 alexjlzheng@gmail.com wrote: > Subject: [PATCH] mm: make pcp decay work with onhz "NOHZ". > Date: Fri, 11 Oct 2024 18:36:10 +0800 > X-Mailer: git-send-email 2.39.3 > > From: MengEn Sun > > when a cpu stops tick, quiet_vmstat may flush all the per cpu > statistics counter. > > while, the shepherd is needed those counters to kick the > vmstat_work. > > when a cpu in nohz with a lot of pcp pages, and do not do page > allocating and freeing. the pcp pages of the cpu may not be hold > for a long time > > we make shepherd keep a eye on the pcp high_min and high_max I can see what you're saying here, but it's hard to understand. Please spend a little time clarifying the text? And please start sentences with a capital letter! > --- a/mm/vmstat.c > +++ b/mm/vmstat.c > @@ -2024,8 +2024,13 @@ static bool need_update(int cpu) > > for_each_populated_zone(zone) { > struct per_cpu_zonestat *pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu); > + struct per_cpu_pages *pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu); > struct per_cpu_nodestat *n; > > + /* in onhz or nohz full make pcp decay work */ "NOHZ". > + if (pcp->high_max > pcp->high_min) > + return true; > + > /* > * The fast way of checking if there are any vmstat diffs. > */ > --