linux-kernel - Re: [ckrm-tech] [RFC][PATCH 5/7] UBC: kernel memory accounting (core)

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Message-ID: <44E98069.3030908@sw.ru>
Date:	Mon, 21 Aug 2006 13:44:09 +0400
From:	Kirill Korotaev <dev@...ru>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Dave Hansen <haveblue@...ibm.com>, rohitseth@...gle.com,
	Rik van Riel <riel@...hat.com>,
	ckrm-tech@...ts.sourceforge.net,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrey Savochkin <saw@...ru>, devel@...nvz.org,
	hugh@...itas.com, Ingo Molnar <mingo@...e.hu>,
	Pavel Emelianov <xemul@...nvz.org>, Andi Kleen <ak@...e.de>,
	Andy Whitcroft <apw@...dowen.org>
Subject: Re: [ckrm-tech] [RFC][PATCH 5/7] UBC: kernel memory accounting	(core)

Alan Cox wrote:
> Ar Gwe, 2006-08-18 am 12:32 -0700, ysgrifennodd Dave Hansen:
> 
>>>It ought to be cheap. Given each set of page structs is an array its a
>>>simple subtract and divide (or with care and people try to pack them
>>>nicely for cache lines - shift) to get to the parallel accounting array.
>>
>>I wish page structs were just a simple array. ;)
> 
> 
> Note I very carefully said "each set of"
> 
> 
>>It will just be a bit more code, but we'll need this for the two other
>>memory models: sparsemem and discontigmem.  For discontig, we'll just
>>need pointers in the pg_data_ts and, for sparsemem, we'll likely need
>>another pointer in the 'struct mem_section'.
> 
> 
> Actually I don't believe this is true in either case. Change the code
> which allocates the page arrays to allocate (+ sizeof(void *) *
> pages_in_array on the end of each array when using UBC. The rest then
> seems to come out naturally.
I only doubt what gain we will have in this situation.
boot-time selectable vs. CONFIG-selectable?

Kirill

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