This reverts commit 95e7a450b8190673675836bfef236262ceff084a.
When I tested thpscale with v6.3 kernel, I found the compaction efficiency
had a great regression compared to v6.2-rc1 kernel. See below numbers:
v6.2-rc v6.3
Percentage huge-3 81.35 ( 0.00%) 32.97 ( -59.47%)
Percentage huge-5 89.92 ( 0.00%) 41.70 ( -53.63%)
Percentage huge-7 92.41 ( 0.00%) 34.08 ( -63.12%)
Percentage huge-12 90.29 ( 0.00%) 41.10 ( -54.49%)
Percentage huge-18 82.38 ( 0.00%) 41.24 ( -49.95%)
Percentage huge-24 80.34 ( 0.00%) 35.99 ( -55.20%)
Percentage huge-30 88.90 ( 0.00%) 44.20 ( -50.28%)
Percentage huge-32 90.69 ( 0.00%) 79.57 ( -12.25%)
Ops Compaction stalls 113790.00 207099.00
Ops Compaction success 33983.00 19488.00
Ops Compaction failures 79807.00 187611.00
Ops Compaction efficiency 29.86 9.41
After some investigation, I found the commit 95e7a450b819
("Revert mm/compaction: fix set skip in fast_find_migrateblock") caused
the regression. This commit revert the commit 7efc3b726103 ("mm/compaction:
fix set skip in fast_find_migrateblock") to fix a CPU stalling issue, which
is caused by compaction stucked in repeating fast_find_migrateblock().
And now the compaction stalling issue is addressed by commit cfccd2e63e7e
("mm, compaction: finish pageblocks on complete migration failure"). So
we should revert the temporary fix by commit 95e7a450b819, since the
fast pfn found by fast_find_migrateblock() really can help to isolate
some migratable pages.
After reverting the commit, the regression has gone.
v6.2-rc1 v6.3 v6.3_patched
Percentage huge-3 81.35 ( 0.00%) 32.97 ( -59.47%) 87.78 ( 7.90%)
Percentage huge-5 89.92 ( 0.00%) 41.70 ( -53.63%) 89.68 ( -0.27%)
Percentage huge-7 92.41 ( 0.00%) 34.08 ( -63.12%) 85.89 ( -7.05%)
Percentage huge-12 90.29 ( 0.00%) 41.10 ( -54.49%) 94.10 ( 4.22%)
Percentage huge-18 82.38 ( 0.00%) 41.24 ( -49.95%) 85.06 ( 3.25%)
Percentage huge-24 80.34 ( 0.00%) 35.99 ( -55.20%) 84.38 ( 5.02%)
Percentage huge-30 88.90 ( 0.00%) 44.20 ( -50.28%) 95.54 ( 7.48%)
Percentage huge-32 90.69 ( 0.00%) 79.57 ( -12.25%) 92.30 ( 1.78%)
Signed-off-by: Baolin Wang <[email protected]>
---
mm/compaction.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 33650541bebc..567c8d41d01e 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1860,7 +1860,6 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc)
pfn = cc->zone->zone_start_pfn;
cc->fast_search_fail = 0;
found_block = true;
- set_pageblock_skip(freepage);
break;
}
}
--
2.27.0
On 4/26/23 17:03, Baolin Wang wrote:
> This reverts commit 95e7a450b8190673675836bfef236262ceff084a.
>
> When I tested thpscale with v6.3 kernel, I found the compaction efficiency
> had a great regression compared to v6.2-rc1 kernel. See below numbers:
> v6.2-rc v6.3
> Percentage huge-3 81.35 ( 0.00%) 32.97 ( -59.47%)
> Percentage huge-5 89.92 ( 0.00%) 41.70 ( -53.63%)
> Percentage huge-7 92.41 ( 0.00%) 34.08 ( -63.12%)
> Percentage huge-12 90.29 ( 0.00%) 41.10 ( -54.49%)
> Percentage huge-18 82.38 ( 0.00%) 41.24 ( -49.95%)
> Percentage huge-24 80.34 ( 0.00%) 35.99 ( -55.20%)
> Percentage huge-30 88.90 ( 0.00%) 44.20 ( -50.28%)
> Percentage huge-32 90.69 ( 0.00%) 79.57 ( -12.25%)
>
> Ops Compaction stalls 113790.00 207099.00
> Ops Compaction success 33983.00 19488.00
> Ops Compaction failures 79807.00 187611.00
> Ops Compaction efficiency 29.86 9.41
>
> After some investigation, I found the commit 95e7a450b819
> ("Revert mm/compaction: fix set skip in fast_find_migrateblock") caused
> the regression. This commit revert the commit 7efc3b726103 ("mm/compaction:
> fix set skip in fast_find_migrateblock") to fix a CPU stalling issue, which
> is caused by compaction stucked in repeating fast_find_migrateblock().
>
> And now the compaction stalling issue is addressed by commit cfccd2e63e7e
> ("mm, compaction: finish pageblocks on complete migration failure"). So
IIRC at that time I was pointing out some scenarios that could make the
problem appear even after that commit, and we wanted to revisit that
when Mel is back.
> we should revert the temporary fix by commit 95e7a450b819, since the
> fast pfn found by fast_find_migrateblock() really can help to isolate
> some migratable pages.
So thanks for the reminder, yet we should make sure the fix is complete
before removing the workaround.
> After reverting the commit, the regression has gone.
> v6.2-rc1 v6.3 v6.3_patched
> Percentage huge-3 81.35 ( 0.00%) 32.97 ( -59.47%) 87.78 ( 7.90%)
> Percentage huge-5 89.92 ( 0.00%) 41.70 ( -53.63%) 89.68 ( -0.27%)
> Percentage huge-7 92.41 ( 0.00%) 34.08 ( -63.12%) 85.89 ( -7.05%)
> Percentage huge-12 90.29 ( 0.00%) 41.10 ( -54.49%) 94.10 ( 4.22%)
> Percentage huge-18 82.38 ( 0.00%) 41.24 ( -49.95%) 85.06 ( 3.25%)
> Percentage huge-24 80.34 ( 0.00%) 35.99 ( -55.20%) 84.38 ( 5.02%)
> Percentage huge-30 88.90 ( 0.00%) 44.20 ( -50.28%) 95.54 ( 7.48%)
> Percentage huge-32 90.69 ( 0.00%) 79.57 ( -12.25%) 92.30 ( 1.78%)
>
> Signed-off-by: Baolin Wang <[email protected]>
> ---
> mm/compaction.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 33650541bebc..567c8d41d01e 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1860,7 +1860,6 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc)
> pfn = cc->zone->zone_start_pfn;
> cc->fast_search_fail = 0;
> found_block = true;
> - set_pageblock_skip(freepage);
> break;
> }
> }
On Wed, Apr 26, 2023 at 05:10:14PM +0200, Vlastimil Babka wrote:
> On 4/26/23 17:03, Baolin Wang wrote:
> > This reverts commit 95e7a450b8190673675836bfef236262ceff084a.
> >
> > When I tested thpscale with v6.3 kernel, I found the compaction efficiency
> > had a great regression compared to v6.2-rc1 kernel. See below numbers:
> > v6.2-rc v6.3
> > Percentage huge-3 81.35 ( 0.00%) 32.97 ( -59.47%)
> > Percentage huge-5 89.92 ( 0.00%) 41.70 ( -53.63%)
> > Percentage huge-7 92.41 ( 0.00%) 34.08 ( -63.12%)
> > Percentage huge-12 90.29 ( 0.00%) 41.10 ( -54.49%)
> > Percentage huge-18 82.38 ( 0.00%) 41.24 ( -49.95%)
> > Percentage huge-24 80.34 ( 0.00%) 35.99 ( -55.20%)
> > Percentage huge-30 88.90 ( 0.00%) 44.20 ( -50.28%)
> > Percentage huge-32 90.69 ( 0.00%) 79.57 ( -12.25%)
> >
> > Ops Compaction stalls 113790.00 207099.00
> > Ops Compaction success 33983.00 19488.00
> > Ops Compaction failures 79807.00 187611.00
> > Ops Compaction efficiency 29.86 9.41
> >
> > After some investigation, I found the commit 95e7a450b819
> > ("Revert mm/compaction: fix set skip in fast_find_migrateblock") caused
> > the regression. This commit revert the commit 7efc3b726103 ("mm/compaction:
> > fix set skip in fast_find_migrateblock") to fix a CPU stalling issue, which
> > is caused by compaction stucked in repeating fast_find_migrateblock().
> >
> > And now the compaction stalling issue is addressed by commit cfccd2e63e7e
> > ("mm, compaction: finish pageblocks on complete migration failure"). So
>
> IIRC at that time I was pointing out some scenarios that could make the
> problem appear even after that commit, and we wanted to revisit that
> when Mel is back.
>
Yes, I've prototyped the fix against 6.3-rc7 and the revert is at the
end but the revert on its own has the potential for causing problems. The
series needs to be rebased, retested and posted. What I last tested
should show up shortly at
https://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git/ mm-follupfastmigrate-v1r1
--
Mel Gorman
SUSE Labs
On 4/26/2023 11:33 PM, Mel Gorman wrote:
> On Wed, Apr 26, 2023 at 05:10:14PM +0200, Vlastimil Babka wrote:
>> On 4/26/23 17:03, Baolin Wang wrote:
>>> This reverts commit 95e7a450b8190673675836bfef236262ceff084a.
>>>
>>> When I tested thpscale with v6.3 kernel, I found the compaction efficiency
>>> had a great regression compared to v6.2-rc1 kernel. See below numbers:
>>> v6.2-rc v6.3
>>> Percentage huge-3 81.35 ( 0.00%) 32.97 ( -59.47%)
>>> Percentage huge-5 89.92 ( 0.00%) 41.70 ( -53.63%)
>>> Percentage huge-7 92.41 ( 0.00%) 34.08 ( -63.12%)
>>> Percentage huge-12 90.29 ( 0.00%) 41.10 ( -54.49%)
>>> Percentage huge-18 82.38 ( 0.00%) 41.24 ( -49.95%)
>>> Percentage huge-24 80.34 ( 0.00%) 35.99 ( -55.20%)
>>> Percentage huge-30 88.90 ( 0.00%) 44.20 ( -50.28%)
>>> Percentage huge-32 90.69 ( 0.00%) 79.57 ( -12.25%)
>>>
>>> Ops Compaction stalls 113790.00 207099.00
>>> Ops Compaction success 33983.00 19488.00
>>> Ops Compaction failures 79807.00 187611.00
>>> Ops Compaction efficiency 29.86 9.41
>>>
>>> After some investigation, I found the commit 95e7a450b819
>>> ("Revert mm/compaction: fix set skip in fast_find_migrateblock") caused
>>> the regression. This commit revert the commit 7efc3b726103 ("mm/compaction:
>>> fix set skip in fast_find_migrateblock") to fix a CPU stalling issue, which
>>> is caused by compaction stucked in repeating fast_find_migrateblock().
>>>
>>> And now the compaction stalling issue is addressed by commit cfccd2e63e7e
>>> ("mm, compaction: finish pageblocks on complete migration failure"). So
>>
>> IIRC at that time I was pointing out some scenarios that could make the
>> problem appear even after that commit, and we wanted to revisit that
>> when Mel is back.
Ah, I missed that, and will check previous discussion.
> Yes, I've prototyped the fix against 6.3-rc7 and the revert is at the
> end but the revert on its own has the potential for causing problems. The
> series needs to be rebased, retested and posted. What I last tested
> should show up shortly at
>
> https://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git/ mm-follupfastmigrate-v1r1
Thanks.