linux-kernel - Re: [PATCH] mm, compaction: properly signal and act upon lock and need

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Message-ID: <5371DCD2.8030602@suse.cz>
Date:	Tue, 13 May 2014 10:50:26 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	David Rientjes <rientjes@...gle.com>
CC:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Greg Thelen <gthelen@...gle.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Minchan Kim <minchan@...nel.org>,
	Mel Gorman <mgorman@...e.de>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Christoph Lameter <cl@...ux.com>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH] mm, compaction: properly signal and act upon lock and
 need_sched() contention

On 05/12/2014 10:28 PM, David Rientjes wrote:
> On Mon, 12 May 2014, Vlastimil Babka wrote:
>
>> diff --git a/mm/compaction.c b/mm/compaction.c
>> index 83ca6f9..b34ab7c 100644
>> --- a/mm/compaction.c
>> +++ b/mm/compaction.c
>> @@ -222,6 +222,27 @@ static bool compact_checklock_irqsave(spinlock_t *lock, unsigned long *flags,
>>   	return true;
>>   }
>>
>> +/*
>> + * Similar to compact_checklock_irqsave() (see its comment) for places where
>> + * a zone lock is not concerned.
>> + *
>> + * Returns false when compaction should abort.
>> + */
>
> I think we should have some sufficient commentary in the code that
> describes why we do this.

Well I can of course mostly duplicate the comment of 
compact_checklock_irqsave() instead of referring to it, if you think 
that's better.

>> +static inline bool compact_check_resched(struct compact_control *cc)
>> +{
>
> I'm not sure that compact_check_resched() is the appropriate name.  Sure,
> it specifies what the current implementation is, but what it's really
> actually doing is determining when compaction should abort prematurely.
>
> Something like compact_should_abort()?

I tried to be somewhat analogous to the name of 
compact_checklock_irqsave(). compact_should_abort() doesn't indicate 
that there might be a resched().
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