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Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v2 4/8] mm/compaction: correct comment of fast_find_migrateblock in isolate_migratepages To: Kemeng Shi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mgorman@techsingularity.net, david@redhat.com References: <20230802093741.2333325-1-shikemeng@huaweicloud.com> <20230802093741.2333325-5-shikemeng@huaweicloud.com> From: Baolin Wang In-Reply-To: <20230802093741.2333325-5-shikemeng@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: D8190C001C X-Stat-Signature: yxcbo9fzoy87xtyd58irmtbu5hrqyia9 X-HE-Tag: 1690975871-55039 X-HE-Meta: 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 7npwbb1P tDXfqZMQU9tr3rn41rVBMMiYzi6rBPvEJt0sXV9DsO1m9V3x8zaB+QspZNr0Q0/w+pw0JZuX2Ke1W88yqOdVpzC134dgIbpYXqwtnbnjRN37quEC8uWgInqTYQti+8ySHTV0uCvtfHfMIkpjalzhSflFNrJH19MLLR6b98LNQwl7Lqp4A7+Li3xSgAw== 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 8/2/2023 5:37 PM, Kemeng Shi wrote: > After 90ed667c03fe5 ("Revert "Revert "mm/compaction: fix set skip in > fast_find_migrateblock"""), we remove skip set in fast_find_migrateblock. > Correct comment that fast_find_block is used to avoid isolation_suitable > check for pageblock returned from fast_find_migrateblock because > fast_find_migrateblock will mark found pageblock skipped. > Instead, comment that fast_find_block is used to avoid a redundant check > of fast found pageblock which is already checked skip flag inside > fast_find_migrateblock. > > Signed-off-by: Kemeng Shi > --- > mm/compaction.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 984c17a5c8fd..5c9dc4049e8e 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1966,8 +1966,8 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) > block_start_pfn = cc->zone->zone_start_pfn; > > /* > - * fast_find_migrateblock marks a pageblock skipped so to avoid > - * the isolation_suitable check below, check whether the fast > + * fast_find_migrateblock will ignore pageblock skipped, so to avoid These seem confusing to me, since the fast_find_migrateblock() did not ignore the skip flag checking. So how about below words? "fast_find_migrateblock() has already ensured the pageblock is not set with a skipped flag, so to avoid the isolation_suitable check below again ..." > + * the isolation_suitable check below again, check whether the fast > * search was successful. > */ > fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail;