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Mon, 24 Apr 2023 19:11:20 -0700 (PDT) Received: from localhost ([2620:10d:c091:400::5:9fc5]) by smtp.gmail.com with ESMTPSA id y6-20020ae9f406000000b0074d60b697a6sm3997382qkl.12.2023.04.24.19.11.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Apr 2023 19:11:20 -0700 (PDT) Date: Mon, 24 Apr 2023 22:11:19 -0400 From: Johannes Weiner To: "Huang, Ying" Cc: linux-mm@kvack.org, Kaiyang Zhao , Mel Gorman , Vlastimil Babka , David Rientjes , linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [RFC PATCH 14/26] mm: compaction: simplify should_compact_retry() Message-ID: <20230425021119.GA5666@cmpxchg.org> References: <20230418191313.268131-1-hannes@cmpxchg.org> <20230418191313.268131-15-hannes@cmpxchg.org> <87v8hkkcds.fsf@yhuang6-desk2.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87v8hkkcds.fsf@yhuang6-desk2.ccr.corp.intel.com> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: EDCF7A0017 X-Rspam-User: X-Stat-Signature: 1menw5hs3t64xprob1ojwqcr3tz98wnf X-HE-Tag: 1682388681-1368 X-HE-Meta: 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 Anb0XwsY 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 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, Apr 25, 2023 at 08:56:47AM +0800, Huang, Ying wrote: > Johannes Weiner writes: > > > The different branches for retry are unnecessarily complicated. There > > is really only three outcomes: progress, skipped, failed. Also, the > > retry counter only applies to loops that made progress, move it there. > > > > Signed-off-by: Johannes Weiner > > --- > > mm/page_alloc.c | 60 +++++++++++++++++-------------------------------- > > 1 file changed, 20 insertions(+), 40 deletions(-) > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index c3b7dc479936..18fa2bbba44b 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -4608,7 +4608,6 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, > > enum compact_priority *compact_priority, > > int *compaction_retries) > > { > > - int max_retries = MAX_COMPACT_RETRIES; > > int min_priority; > > bool ret = false; > > int retries = *compaction_retries; > > @@ -4621,19 +4620,27 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, > > return false; > > > > /* > > - * Compaction managed to coalesce some page blocks, but the > > - * allocation failed presumably due to a race. Retry some. > > + * Compaction coalesced some page blocks, but the allocation > > + * failed, presumably due to a race. Retry a few times. > > */ > > - if (compact_result == COMPACT_SUCCESS) > > - (*compaction_retries)++; > > + if (compact_result == COMPACT_SUCCESS) { > > + int max_retries = MAX_COMPACT_RETRIES; > > > > - /* > > - * All zones were scanned completely and still no result. It > > - * doesn't really make much sense to retry except when the > > - * failure could be caused by insufficient priority > > - */ > > - if (compact_result == COMPACT_COMPLETE) > > - goto check_priority; > > + /* > > + * !costly requests are much more important than > > + * __GFP_RETRY_MAYFAIL costly ones because they are de > > + * facto nofail and invoke OOM killer to move on while > > + * costly can fail and users are ready to cope with > > + * that. 1/4 retries is rather arbitrary but we would > > + * need much more detailed feedback from compaction to > > + * make a better decision. > > + */ > > + if (order > PAGE_ALLOC_COSTLY_ORDER) > > + max_retries /= 4; > > + > > + ret = ++(*compaction_retries) <= MAX_COMPACT_RETRIES; > ~~~~~~~~~~~~~~~~~~~ > > Should be max_retries? Good catch. max_retries is deleted in a later patch, but this one should be fixed regardless. Thanks, I will correct it.