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rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH 1/5] mm/compaction: allow blockpfn outside of pageblock for high order buddy page To: Kemeng Shi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org Cc: mgorman@techsingularity.net, willy@infradead.org, david@redhat.com References: <20230729174354.2239980-1-shikemeng@huaweicloud.com> <20230729174354.2239980-2-shikemeng@huaweicloud.com> From: Baolin Wang In-Reply-To: <20230729174354.2239980-2-shikemeng@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: EDF2EA000D X-Rspam-User: X-Stat-Signature: amejb867gitaqn6ttwwm88od35xb4814 X-Rspamd-Server: rspam01 X-HE-Tag: 1690941434-628843 X-HE-Meta: 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 aPxJMnhO MDVTa0fn4wigWxgG2JV/PoJx/ID4H32IAwY9Vdvcel4RHR0ibcZv0E2K9wxIYeyhRJckffCrkbB4pGoNiqtSwLU44estxrx9w9SQtte/dsmQTrSmmTlRdd9kAdNDRhaAS9Z76c6jat7Lop2w= 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 7/30/2023 1:43 AM, Kemeng Shi wrote: > Commit 9fcd6d2e052ee ("mm, compaction: skip compound pages by order in > free scanner") skiped compound pages to save iterations and limit blockpfn > to reach outside of page block in case of bogus compound_order. While this > also limit pfnblock outside page block in case a buddy page with order > higher than page block is found. After this, isolate_freepages_range will > fail unexpectedly as it will fail to isolate the page block which was > isolated successfully by high order buddy page in previous page block > and abort the free page isolation. Not sure I uderstand the problem, why the isolate_freepages_range() will fail? In isolate_freepages_range(), it did not use the 'blockpfn' cursor to try next candidate pfn, instead using the 'isolated' to calculate next cursor. Or I missed something else? > Fix this by allow blockpfn outside of pageblock in case of high order > buddy page. > > Fixes: 9fcd6d2e052ee ("mm, compaction: skip compound pages by order in free scanner") > Signed-off-by: Kemeng Shi > --- > mm/compaction.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 6841c0496223..d1d28d57e5bd 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -681,8 +681,10 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > /* > * There is a tiny chance that we have read bogus compound_order(), > * so be careful to not go outside of the pageblock. > + * Allow blockpfn outside pageblock in normal case that we isolate > + * buddy page with order more than pageblock order. > */ > - if (unlikely(blockpfn > end_pfn)) > + if (unlikely(blockpfn > end_pfn) && total_isolated <= pageblock_nr_pages) > blockpfn = end_pfn; > > trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn, > @@ -1418,7 +1420,7 @@ fast_isolate_around(struct compact_control *cc, unsigned long pfn) > isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false); > > /* Skip this pageblock in the future as it's full or nearly full */ > - if (start_pfn == end_pfn && !cc->no_set_skip_hint) > + if (start_pfn >= end_pfn && !cc->no_set_skip_hint) > set_pageblock_skip(page); > } > > @@ -1687,7 +1689,7 @@ static void isolate_freepages(struct compact_control *cc) > block_end_pfn, freelist, stride, false); > > /* Update the skip hint if the full pageblock was scanned */ > - if (isolate_start_pfn == block_end_pfn) > + if (isolate_start_pfn >= block_end_pfn) > update_pageblock_skip(cc, page, block_start_pfn); > > /* Are enough freepages isolated? */