| Message ID | 20230728171037.2219226-5-shikemeng@huaweicloud.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Fixes and cleanups to compaction | expand |
On 7/29/2023 1:10 AM, Kemeng Shi wrote: > In old code, we set skip to found page block in fast_find_migrateblock. So > we use fast_find_block to avoid skip found page block from > fast_find_migrateblock. > In 90ed667c03fe5 ("Revert "Revert "mm/compaction: fix set skip in > fast_find_migrateblock"""), we remove skip set in fast_find_migrateblock, > then fast_find_block is useless. > > Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com> > --- > mm/compaction.c | 12 +----------- > 1 file changed, 1 insertion(+), 11 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index ad535f880c70..09c36251c613 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1949,7 +1949,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) > const isolate_mode_t isolate_mode = > (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | > (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0); > - bool fast_find_block; > > /* > * Start at where we last stopped, or beginning of the zone as > @@ -1961,13 +1960,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) > if (block_start_pfn < cc->zone->zone_start_pfn) > 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 > - * search was successful. > - */ > - fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail; > - > /* Only scan within a pageblock boundary */ > block_end_pfn = pageblock_end_pfn(low_pfn); > > @@ -1976,7 +1968,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) > * Do not cross the free scanner. > */ > for (; block_end_pfn <= cc->free_pfn; > - fast_find_block = false, > cc->migrate_pfn = low_pfn = block_end_pfn, > block_start_pfn = block_end_pfn, > block_end_pfn += pageblock_nr_pages) { > @@ -2007,8 +1998,7 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) > * before making it "skip" so other compaction instances do > * not scan the same block. > */ > - if (pageblock_aligned(low_pfn) && > - !fast_find_block && !isolation_suitable(cc, page)) > + if (pageblock_aligned(low_pfn) && !isolation_suitable(cc, page)) I do not think so. If the pageblock is found by fast_find_migrateblock(), that means it definitely has not been set the skip flag, so there is not need to call isolation_suitable() if fast_find_block is true, right?
on 8/1/2023 10:42 AM, Baolin Wang wrote: > > > On 7/29/2023 1:10 AM, Kemeng Shi wrote: >> In old code, we set skip to found page block in fast_find_migrateblock. So >> we use fast_find_block to avoid skip found page block from >> fast_find_migrateblock. >> In 90ed667c03fe5 ("Revert "Revert "mm/compaction: fix set skip in >> fast_find_migrateblock"""), we remove skip set in fast_find_migrateblock, >> then fast_find_block is useless. >> >> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com> >> --- >> mm/compaction.c | 12 +----------- >> 1 file changed, 1 insertion(+), 11 deletions(-) >> >> diff --git a/mm/compaction.c b/mm/compaction.c >> index ad535f880c70..09c36251c613 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -1949,7 +1949,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >> const isolate_mode_t isolate_mode = >> (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | >> (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0); >> - bool fast_find_block; >> /* >> * Start at where we last stopped, or beginning of the zone as >> @@ -1961,13 +1960,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >> if (block_start_pfn < cc->zone->zone_start_pfn) >> 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 >> - * search was successful. >> - */ >> - fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail; >> - >> /* Only scan within a pageblock boundary */ >> block_end_pfn = pageblock_end_pfn(low_pfn); >> @@ -1976,7 +1968,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >> * Do not cross the free scanner. >> */ >> for (; block_end_pfn <= cc->free_pfn; >> - fast_find_block = false, >> cc->migrate_pfn = low_pfn = block_end_pfn, >> block_start_pfn = block_end_pfn, >> block_end_pfn += pageblock_nr_pages) { >> @@ -2007,8 +1998,7 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >> * before making it "skip" so other compaction instances do >> * not scan the same block. >> */ >> - if (pageblock_aligned(low_pfn) && >> - !fast_find_block && !isolation_suitable(cc, page)) >> + if (pageblock_aligned(low_pfn) && !isolation_suitable(cc, page)) > > I do not think so. If the pageblock is found by fast_find_migrateblock(), that means it definitely has not been set the skip flag, so there is not need to call isolation_suitable() if fast_find_block is true, right? > > Actually, found pageblock could be set skip as: 1. other compactor could mark this pageblock as skip after zone lock is realeased in fast_find_migrateblock. 2. fast_find_migrateblock may uses pfn from reinit_migrate_pfn which is previously found and sacnned. It could be fully sacnned and marked skip after it's first return from fast_find_migrateblock and it should be skipped. Thanks!
On 8/1/2023 11:24 AM, Kemeng Shi wrote: > > > on 8/1/2023 10:42 AM, Baolin Wang wrote: >> >> >> On 7/29/2023 1:10 AM, Kemeng Shi wrote: >>> In old code, we set skip to found page block in fast_find_migrateblock. So >>> we use fast_find_block to avoid skip found page block from >>> fast_find_migrateblock. >>> In 90ed667c03fe5 ("Revert "Revert "mm/compaction: fix set skip in >>> fast_find_migrateblock"""), we remove skip set in fast_find_migrateblock, >>> then fast_find_block is useless. >>> >>> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com> >>> --- >>> mm/compaction.c | 12 +----------- >>> 1 file changed, 1 insertion(+), 11 deletions(-) >>> >>> diff --git a/mm/compaction.c b/mm/compaction.c >>> index ad535f880c70..09c36251c613 100644 >>> --- a/mm/compaction.c >>> +++ b/mm/compaction.c >>> @@ -1949,7 +1949,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>> const isolate_mode_t isolate_mode = >>> (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | >>> (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0); >>> - bool fast_find_block; >>> /* >>> * Start at where we last stopped, or beginning of the zone as >>> @@ -1961,13 +1960,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>> if (block_start_pfn < cc->zone->zone_start_pfn) >>> 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 >>> - * search was successful. >>> - */ >>> - fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail; >>> - >>> /* Only scan within a pageblock boundary */ >>> block_end_pfn = pageblock_end_pfn(low_pfn); >>> @@ -1976,7 +1968,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>> * Do not cross the free scanner. >>> */ >>> for (; block_end_pfn <= cc->free_pfn; >>> - fast_find_block = false, >>> cc->migrate_pfn = low_pfn = block_end_pfn, >>> block_start_pfn = block_end_pfn, >>> block_end_pfn += pageblock_nr_pages) { >>> @@ -2007,8 +1998,7 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>> * before making it "skip" so other compaction instances do >>> * not scan the same block. >>> */ >>> - if (pageblock_aligned(low_pfn) && >>> - !fast_find_block && !isolation_suitable(cc, page)) >>> + if (pageblock_aligned(low_pfn) && !isolation_suitable(cc, page)) >> >> I do not think so. If the pageblock is found by fast_find_migrateblock(), that means it definitely has not been set the skip flag, so there is not need to call isolation_suitable() if fast_find_block is true, right? >> >> > Actually, found pageblock could be set skip as: > 1. other compactor could mark this pageblock as skip after zone lock is realeased > in fast_find_migrateblock. Yes, but your patch also can not close this race window, that means it can also be set skip flag after the isolation_suitable() validation by other compactors. > 2. fast_find_migrateblock may uses pfn from reinit_migrate_pfn which is previously found > and sacnned. It could be fully sacnned and marked skip after it's first return from Right, but now the 'fast_find_block' is false, and we will call isolation_suitable() to validate the skip flag. > fast_find_migrateblock and it should be skipped. > Thanks!
on 8/1/2023 11:34 AM, Baolin Wang wrote: > > > On 8/1/2023 11:24 AM, Kemeng Shi wrote: >> >> >> on 8/1/2023 10:42 AM, Baolin Wang wrote: >>> >>> >>> On 7/29/2023 1:10 AM, Kemeng Shi wrote: >>>> In old code, we set skip to found page block in fast_find_migrateblock. So >>>> we use fast_find_block to avoid skip found page block from >>>> fast_find_migrateblock. >>>> In 90ed667c03fe5 ("Revert "Revert "mm/compaction: fix set skip in >>>> fast_find_migrateblock"""), we remove skip set in fast_find_migrateblock, >>>> then fast_find_block is useless. >>>> >>>> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com> >>>> --- >>>> mm/compaction.c | 12 +----------- >>>> 1 file changed, 1 insertion(+), 11 deletions(-) >>>> >>>> diff --git a/mm/compaction.c b/mm/compaction.c >>>> index ad535f880c70..09c36251c613 100644 >>>> --- a/mm/compaction.c >>>> +++ b/mm/compaction.c >>>> @@ -1949,7 +1949,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>>> const isolate_mode_t isolate_mode = >>>> (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | >>>> (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0); >>>> - bool fast_find_block; >>>> /* >>>> * Start at where we last stopped, or beginning of the zone as >>>> @@ -1961,13 +1960,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>>> if (block_start_pfn < cc->zone->zone_start_pfn) >>>> 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 >>>> - * search was successful. >>>> - */ >>>> - fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail; >>>> - >>>> /* Only scan within a pageblock boundary */ >>>> block_end_pfn = pageblock_end_pfn(low_pfn); >>>> @@ -1976,7 +1968,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>>> * Do not cross the free scanner. >>>> */ >>>> for (; block_end_pfn <= cc->free_pfn; >>>> - fast_find_block = false, >>>> cc->migrate_pfn = low_pfn = block_end_pfn, >>>> block_start_pfn = block_end_pfn, >>>> block_end_pfn += pageblock_nr_pages) { >>>> @@ -2007,8 +1998,7 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>>> * before making it "skip" so other compaction instances do >>>> * not scan the same block. >>>> */ >>>> - if (pageblock_aligned(low_pfn) && >>>> - !fast_find_block && !isolation_suitable(cc, page)) >>>> + if (pageblock_aligned(low_pfn) && !isolation_suitable(cc, page)) >>> >>> I do not think so. If the pageblock is found by fast_find_migrateblock(), that means it definitely has not been set the skip flag, so there is not need to call isolation_suitable() if fast_find_block is true, right? >>> >>> >> Actually, found pageblock could be set skip as: >> 1. other compactor could mark this pageblock as skip after zone lock is realeased >> in fast_find_migrateblock. > > Yes, but your patch also can not close this race window, that means it can also be set skip flag after the isolation_suitable() validation by other compactors. > Yes, I think it's still worth to remove a lot of fast_find_block relevant check and reduce code complexity with one redundant isolation_suitable which may skip some block with luck. >> 2. fast_find_migrateblock may uses pfn from reinit_migrate_pfn which is previously found >> and sacnned. It could be fully sacnned and marked skip after it's first return from > > Right, but now the 'fast_find_block' is false, and we will call isolation_suitable() to validate the skip flag. > Right, sorry for missing that. But it's ok to keep the fast_find_block if you insist and I will just correct the stale comment that "fast_find_migrateblock marks a pageblock skipped ..." in next version. Thanks! >> fast_find_migrateblock and it should be skipped. >> Thanks! >
On 8/1/2023 11:48 AM, Kemeng Shi wrote: > > > on 8/1/2023 11:34 AM, Baolin Wang wrote: >> >> >> On 8/1/2023 11:24 AM, Kemeng Shi wrote: >>> >>> >>> on 8/1/2023 10:42 AM, Baolin Wang wrote: >>>> >>>> >>>> On 7/29/2023 1:10 AM, Kemeng Shi wrote: >>>>> In old code, we set skip to found page block in fast_find_migrateblock. So >>>>> we use fast_find_block to avoid skip found page block from >>>>> fast_find_migrateblock. >>>>> In 90ed667c03fe5 ("Revert "Revert "mm/compaction: fix set skip in >>>>> fast_find_migrateblock"""), we remove skip set in fast_find_migrateblock, >>>>> then fast_find_block is useless. >>>>> >>>>> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com> >>>>> --- >>>>> mm/compaction.c | 12 +----------- >>>>> 1 file changed, 1 insertion(+), 11 deletions(-) >>>>> >>>>> diff --git a/mm/compaction.c b/mm/compaction.c >>>>> index ad535f880c70..09c36251c613 100644 >>>>> --- a/mm/compaction.c >>>>> +++ b/mm/compaction.c >>>>> @@ -1949,7 +1949,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>>>> const isolate_mode_t isolate_mode = >>>>> (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | >>>>> (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0); >>>>> - bool fast_find_block; >>>>> /* >>>>> * Start at where we last stopped, or beginning of the zone as >>>>> @@ -1961,13 +1960,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>>>> if (block_start_pfn < cc->zone->zone_start_pfn) >>>>> 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 >>>>> - * search was successful. >>>>> - */ >>>>> - fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail; >>>>> - >>>>> /* Only scan within a pageblock boundary */ >>>>> block_end_pfn = pageblock_end_pfn(low_pfn); >>>>> @@ -1976,7 +1968,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>>>> * Do not cross the free scanner. >>>>> */ >>>>> for (; block_end_pfn <= cc->free_pfn; >>>>> - fast_find_block = false, >>>>> cc->migrate_pfn = low_pfn = block_end_pfn, >>>>> block_start_pfn = block_end_pfn, >>>>> block_end_pfn += pageblock_nr_pages) { >>>>> @@ -2007,8 +1998,7 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>>>> * before making it "skip" so other compaction instances do >>>>> * not scan the same block. >>>>> */ >>>>> - if (pageblock_aligned(low_pfn) && >>>>> - !fast_find_block && !isolation_suitable(cc, page)) >>>>> + if (pageblock_aligned(low_pfn) && !isolation_suitable(cc, page)) >>>> >>>> I do not think so. If the pageblock is found by fast_find_migrateblock(), that means it definitely has not been set the skip flag, so there is not need to call isolation_suitable() if fast_find_block is true, right? >>>> >>>> >>> Actually, found pageblock could be set skip as: >>> 1. other compactor could mark this pageblock as skip after zone lock is realeased >>> in fast_find_migrateblock. >> >> Yes, but your patch also can not close this race window, that means it can also be set skip flag after the isolation_suitable() validation by other compactors. >> > Yes, I think it's still worth to remove a lot of fast_find_block relevant check and reduce > code complexity with one redundant isolation_suitable which may skip some block with luck. >>> 2. fast_find_migrateblock may uses pfn from reinit_migrate_pfn which is previously found >>> and sacnned. It could be fully sacnned and marked skip after it's first return from >> >> Right, but now the 'fast_find_block' is false, and we will call isolation_suitable() to validate the skip flag. >> > Right, sorry for missing that. > > But it's ok to keep the fast_find_block if you insist and I will just correct the stale Yes, I still prefer to keep the fast_find_block, since I did not see this patch can fix any real issue and might have a side effect for fast-find-pageblock(?). > comment that "fast_find_migrateblock marks a pageblock skipped ..." in next version. Sure, please do it.
diff --git a/mm/compaction.c b/mm/compaction.c index ad535f880c70..09c36251c613 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1949,7 +1949,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) const isolate_mode_t isolate_mode = (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0); - bool fast_find_block; /* * Start at where we last stopped, or beginning of the zone as @@ -1961,13 +1960,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) if (block_start_pfn < cc->zone->zone_start_pfn) 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 - * search was successful. - */ - fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail; - /* Only scan within a pageblock boundary */ block_end_pfn = pageblock_end_pfn(low_pfn); @@ -1976,7 +1968,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) * Do not cross the free scanner. */ for (; block_end_pfn <= cc->free_pfn; - fast_find_block = false, cc->migrate_pfn = low_pfn = block_end_pfn, block_start_pfn = block_end_pfn, block_end_pfn += pageblock_nr_pages) { @@ -2007,8 +1998,7 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) * before making it "skip" so other compaction instances do * not scan the same block. */ - if (pageblock_aligned(low_pfn) && - !fast_find_block && !isolation_suitable(cc, page)) + if (pageblock_aligned(low_pfn) && !isolation_suitable(cc, page)) continue; /*
In old code, we set skip to found page block in fast_find_migrateblock. So we use fast_find_block to avoid skip found page block from fast_find_migrateblock. In 90ed667c03fe5 ("Revert "Revert "mm/compaction: fix set skip in fast_find_migrateblock"""), we remove skip set in fast_find_migrateblock, then fast_find_block is useless. Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com> --- mm/compaction.c | 12 +----------- 1 file changed, 1 insertion(+), 11 deletions(-)