linux-kernel - Re: [PATCH 1/2] vmscan: fix initial shrinker size handling

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Message-ID: <4E534D13.5020102@openvz.org>
Date:	Tue, 23 Aug 2011 10:47:47 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Dave Chinner <david@...morbit.com>
Subject: Re: [PATCH 1/2] vmscan: fix initial shrinker size handling

Andrew Morton wrote:
<snip>
>>   		long new_nr;
>>   		long batch_size = shrinker->batch ? shrinker->batch
>>   						  : SHRINK_BATCH;
>>
>> +		max_pass = do_shrinker_shrink(shrinker, shrink, 0);
>> +		if (max_pass<= 0)
>> +			continue;
>> +
>>   		/*
>>   		 * copy the current shrinker scan count into a local variable
>>   		 * and zero it so that other concurrent shrinker invocations
>> @@ -266,7 +270,6 @@ unsigned long shrink_slab(struct shrink_control *shrink,
>>   		} while (cmpxchg(&shrinker->nr, nr, 0) != nr);
>>
>>   		total_scan = nr;
>> -		max_pass = do_shrinker_shrink(shrinker, shrink, 0);
>>   		delta = (4 * nr_pages_scanned) / shrinker->seeks;
>>   		delta *= max_pass;
>>   		do_div(delta, lru_pages + 1);
>
> Why was the shrinker call moved to before the alteration of shrinker->nr?

I think, if we skip shrinker we shouldn't reset accumulated pressure,
because next reclaimer (for example with less strict gfp) can use it.
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