On 03/02/2016 02:57 PM, Joonsoo Kim wrote:
2016-03-02 19:04 GMT+09:00 Vlastimil Babka <vbabka@xxxxxxx>:
On 03/02/2016 07:33 AM, Joonsoo Kim wrote:
Why you did the test with THP? THP interferes result of main test so
it would be better not to enable it.
Hmm I've always left it enabled. It makes for a more realistic interference
and would also show unintended regressions in that closely related area.
But, it makes review hard because complex analysis is needed to
understand the result.
Following is the example.
"The compaction stalls
(direct compaction) in the interfering kernel builds (probably THP's) also
decreased somewhat to kcompactd activity, yet THP alloc successes improved a
bit."
So, why do we need this comment to understand effect of this patch? If you did
a test without THP, it would not be necessary.
I see. Next time I'll do a run with THP disabled.
And, this patch increased compaction activity (10 times for migrate
scanned)
may be due to resetting skip block information.
Note that kswapd compaction activity was completely non-existent for reasons
outlined in the changelog.
Isn't is better to disable it
for this patch to work as similar as possible that kswapd does and
re-enable it
on next patch? If something goes bad, it can simply be reverted.
Look like it is even not mentioned in the description.
Yeah skip block information is discussed in the next patch, which mentions
that it's being reset and why. I think it makes more sense, as when kswapd
Yes, I know.
What I'd like to say here is that you need to care current_is_kswapd() in
this patch. This patch unintentionally change the back ground compaction thread
behaviour to restart compaction by every 64 trials because calling
curret_is_kswapd()
> by kcompactd would return false and is treated as direct reclaim.
Oh, you mean this path to reset the skip bits. I see. But if skip bits
are already reset by kswapd when waking kcompactd, then effect of
another (rare) reset in kcompactd itself will be minimal?
Result of patch 4
and patch 5 would be same.
It's certainly possible to fold patch 5 into 4. I posted them separately
mainly to make review more feasible. But the differences in results are
already quite small.
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