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Tue, 10 May 2022 14:44:40 -0700 (PDT) Date: Tue, 10 May 2022 14:44:38 -0700 From: Minchan Kim To: Johannes Weiner Cc: Andrew Morton , LKML , linux-mm , Suren Baghdasaryan , Michal Hocko , John Dias , Tim Murray , Matthew Wilcox , Vladimir Davydov , Martin Liu Subject: Re: [PATCH v3] mm: don't be stuck to rmap lock on reclaim path Message-ID: References: <20220510171100.48500-1-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: E26D11200B7 Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=gkquX5jr; spf=pass (imf29.hostedemail.com: domain of minchan.kim@gmail.com designates 209.85.210.173 as permitted sender) smtp.mailfrom=minchan.kim@gmail.com; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=kernel.org (policy=none) X-Rspam-User: X-Stat-Signature: fhodmit3yjuk1appegebk68wgbgsf8ro X-HE-Tag: 1652219074-429558 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, May 10, 2022 at 02:16:07PM -0400, Johannes Weiner wrote: > Hi Minchan, > > The patch looks reasonable to me, but one thing stands out: > > On Tue, May 10, 2022 at 10:11:00AM -0700, Minchan Kim wrote: > > @@ -1391,6 +1391,10 @@ static enum page_references folio_check_references(struct folio *folio, > > if (vm_flags & VM_LOCKED) > > return PAGEREF_ACTIVATE; > > > > + /* page_referenced didn't work due to lock contention */ > > + if (referenced_ptes == -1) > > + return PAGEREF_KEEP; > > + > > if (referenced_ptes) { > > /* > > * All mapped folios start out with page table > > This means contended inactive pages get rotated. > > > @@ -2492,7 +2496,7 @@ static void shrink_active_list(unsigned long nr_to_scan, > > } > > > > if (folio_referenced(folio, 0, sc->target_mem_cgroup, > > - &vm_flags)) { > > + &vm_flags) > 0) { > > /* > > * Identify referenced, file-backed active pages and > > * give them one more trip around the active list. So > > This means contended active pages do NOT get rotated. > > It's a bit of an arbitrary choice what to do with reclaim candidates > for which you can get no reference information, but staying consistent > is likely a good idea. My preference would be to just rotate contended > pages throughout rather than risk dropping the workingset on the floor. > > /* Referenced or rmap lock contention: rotate */ > if (folio_referenced() != 0) { > ... > > What do you think? Sure, it's good start before adding more heuristic later. Thanks for the review. I will post v4.