From: Joonsoo Kim <js1304@gmail.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Linux Memory Management List <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Andrea Arcangeli <aarcange@redhat.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Rik van Riel <riel@redhat.com>,
Mel Gorman <mgorman@techsingularity.net>,
David Rientjes <rientjes@google.com>,
Michal Hocko <mhocko@suse.com>,
Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH v2 4/5] mm, kswapd: replace kswapd compaction with waking up kcompactd
Date: Wed, 2 Mar 2016 23:22:11 +0900 [thread overview]
Message-ID: <CAAmzW4PGgYkL9xnCXgSQ=8kW0sJkaYyrxenb_XKHcW1wDGMEyw@mail.gmail.com> (raw)
In-Reply-To: <56D6F41D.9080107@suse.cz>
2016-03-02 23:09 GMT+09:00 Vlastimil Babka <vbabka@suse.cz>:
> On 03/02/2016 02:57 PM, Joonsoo Kim wrote:
>>
>> 2016-03-02 19:04 GMT+09:00 Vlastimil Babka <vbabka@suse.cz>:
>>>
>>> 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?
If you care current_is_kswapd() in this patch properly (properly means change
like "current_is_kcompactd()), reset in kswapd would not
happen because, compact_blockskip_flush would not be set by kcompactd.
In this case, patch 5 would have it's own meaning so cannot be folded.
Thanks.
>> 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.
>
next prev parent reply other threads:[~2016-03-02 14:22 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-08 13:38 [PATCH v2 0/5] introduce kcompactd and stop compacting in kswapd Vlastimil Babka
2016-02-08 13:38 ` [PATCH v2 1/5] mm, kswapd: remove bogus check of balance_classzone_idx Vlastimil Babka
2016-02-08 13:38 ` [PATCH v2 2/5] mm, compaction: introduce kcompactd Vlastimil Babka
2016-03-02 6:09 ` Joonsoo Kim
2016-03-02 12:25 ` Vlastimil Babka
2016-02-08 13:38 ` [PATCH v2 3/5] mm, memory hotplug: small cleanup in online_pages() Vlastimil Babka
2016-02-08 13:38 ` [PATCH v2 4/5] mm, kswapd: replace kswapd compaction with waking up kcompactd Vlastimil Babka
2016-02-08 22:58 ` Andrew Morton
2016-02-09 10:53 ` Vlastimil Babka
2016-02-09 10:21 ` Vlastimil Babka
2016-03-01 14:14 ` Vlastimil Babka
2016-03-02 6:33 ` Joonsoo Kim
2016-03-02 10:04 ` Vlastimil Babka
2016-03-02 13:57 ` Joonsoo Kim
2016-03-02 14:09 ` Vlastimil Babka
2016-03-02 14:22 ` Joonsoo Kim [this message]
2016-03-02 14:40 ` Vlastimil Babka
2016-03-02 14:59 ` Joonsoo Kim
2016-03-02 15:22 ` Vlastimil Babka
2016-03-04 23:25 ` Andrew Morton
2016-03-07 9:45 ` Vlastimil Babka
2016-03-09 13:47 ` Vlastimil Babka
2016-03-09 13:50 ` Vlastimil Babka
2016-03-02 12:27 ` Vlastimil Babka
2016-02-08 13:38 ` [PATCH v2 5/5] mm, compaction: adapt isolation_suitable flushing to kcompactd Vlastimil Babka
2016-03-01 14:44 ` Vlastimil Babka
2016-03-09 15:52 ` [PATCH v2 0/5] introduce kcompactd and stop compacting in kswapd Michal Hocko
2016-03-10 8:38 ` Vlastimil Babka
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAAmzW4PGgYkL9xnCXgSQ=8kW0sJkaYyrxenb_XKHcW1wDGMEyw@mail.gmail.com' \
--to=js1304@gmail.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=hannes@cmpxchg.org \
--cc=iamjoonsoo.kim@lge.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@techsingularity.net \
--cc=mhocko@suse.com \
--cc=riel@redhat.com \
--cc=rientjes@google.com \
--cc=vbabka@suse.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).