linux-kernel - Re: [patch] SLQB slab allocator

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Date:	Tue, 3 Feb 2009 20:42:04 +0200
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	Nick Piggin <npiggin@...e.de>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Lin Ming <ming.m.lin@...el.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [patch] SLQB slab allocator

Hi Christoph,

On Tue, Feb 3, 2009 at 7:33 PM, Christoph Lameter
<cl@...ux-foundation.org> wrote:
>> > Trimming through water marks and allocating memory from the page allocator
>> > is going to be very frequent if you continually allocate on one processor
>> > and free on another.
>>
>> Um yes, that's the point. But you previously claimed that it would just
>> grow unconstrained. Which is obviously wrong. So I don't understand what
>> your point is.
>
> It will grow unconstrained if you elect to defer queue processing. That
> was what we discussed.

Well, the slab_hiwater() check in __slab_free() of mm/slqb.c will cap
the size of the queue. But we do the same thing in SLAB with
alien->limit in cache_free_alien() and ac->limit in __cache_free(). So
I'm not sure what you mean when you say that the queues will "grow
unconstrained" (in either of the allocators). Hmm?

                               Pekka
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