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rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH 2/8] mm/compaction: correct last_migrated_pfn update in compact_zone To: Kemeng Shi , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mgorman@techsingularity.net, willy@infradead.org, david@redhat.com References: <20230728171037.2219226-1-shikemeng@huaweicloud.com> <20230728171037.2219226-3-shikemeng@huaweicloud.com> From: Baolin Wang In-Reply-To: <20230728171037.2219226-3-shikemeng@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: E962440012 X-Rspam-User: X-Stat-Signature: wsoisbm99gucxq89tsxp7q8ccn6rz3e4 X-Rspamd-Server: rspam01 X-HE-Tag: 1690855734-882545 X-HE-Meta: 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 tCL1xbcD mpZA4zNsfLZYCGS3CuiZTg3u4vqlQ0mbVd8Fvz5RhgLzb7u7yLZlL2fvV+KQXJ7qXRYGQc9QuOEs4AJkdG/E1p8PN65C6Mbl+5VKbuBu2r8EFvkbw89dkdUhz2crZ4s2BY8/TQNI2yM1UgsiY61ira2N78nQDsCEjN89xnZ3nQFGbrqAG/cOVTJMW8W15v3eUaLeg 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 7/29/2023 1:10 AM, Kemeng Shi wrote: > We record start pfn of last isolated page block with last_migrated_pfn. And > then: > 1. We check if we mark the page block skip for exclusive access in > isolate_migratepages_block by test if next migrate pfn is still in last > isolated page block. If so, we will set finish_pageblock to do the rescan. > 2. We check if a full cc->order block is scanned by test if last scan range > passes the cc->order block boundary. If so, we flush the pages were freed. > > We treat cc->migrate_pfn before isolate_migratepages as the start pfn of > last isolated page range. However, we always align migrate_pfn to page block > or move to another page block in fast_find_migrateblock or in linearly scan > forward in isolate_migratepages before do page isolation in > isolate_migratepages_block. Right. But can you describe the impact in detail if the last_migrated_pfn is not set correctly? For example, this will result in rescan not being set correctly to miss a pageblock's rescanning. Otherwise looks good to me. > Update last_migrated_pfn with pageblock_start_pfn(cc->migrate_pfn - 1) > after scan to correctly set start pfn of last isolated page range. > Signed-off-by: Kemeng Shi > --- > mm/compaction.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index ce7841363b12..fb250c6b2b6e 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -2482,7 +2482,8 @@ compact_zone(struct compact_control *cc, struct capture_control *capc) > goto check_drain; > case ISOLATE_SUCCESS: > update_cached = false; > - last_migrated_pfn = iteration_start_pfn; > + last_migrated_pfn = max(cc->zone->zone_start_pfn, > + pageblock_start_pfn(cc->migrate_pfn - 1)); > } > > err = migrate_pages(&cc->migratepages, compaction_alloc,