linux-kernel - Re: [PATCH 7/8] Scanner changes needed to implement per-container scanner

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Date:	Fri, 01 Jun 2007 11:40:09 +0400
From:	Pavel Emelianov <xemul@...nvz.org>
To:	balbir@...ux.vnet.ibm.com
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Emelianov <xemul@...nvz.org>,
	Paul Menage <menage@...gle.com>,
	Balbir Singh <balbir@...ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	devel@...nvz.org, Kirill Korotaev <dev@...nvz.org>
Subject: Re: [PATCH 7/8] Scanner changes needed to implement per-container
 scanner

Balbir Singh wrote:
> Andrew Morton wrote:
>>> +		nr_reclaimed += shrink_zones(priority, zones, sc);
>>> +		if (sc->cnt == NULL)
>>> +			shrink_slab(sc->nr_scanned, gfp_mask, lru_pages);
>> We don't we shrink slab if called to shrink a container.
>>
>> This is a fundamental design decision, and a design shortcoming.  A full
>> discussion of this is absolutely appropriate to the patch changelog. 
>> Please don't just hide stuff like this in the patch and leave people
>> wondering, or ignorant.
> 
> Yes, we don't because we do not account for slab usage right now. We account
> only for memory allocated to user space. A good fat comment will help here.
> 
> 

I have already added the comment. But the problem is not in that we
do not account for kernel memory. Shrinking slabs won't unmap any
pages from user-space and thus won't help user to charge more. This
will only make kernel suffer from re-creation of objects.

Thanks,
Pavel.
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