linux-kernel - Re: [00/14] Virtual Compound Page Support V3

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Date:	Mon, 24 Mar 2008 11:31:05 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Arjan van de Ven <arjan@...radead.org>
cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [00/14] Virtual Compound Page Support V3

On Sat, 22 Mar 2008, Arjan van de Ven wrote:

> can you document the drawback of large, frequent vmalloc() allocations at least?

Ok. Lets add some documentation about this issue and some other 
things. A similar suggestion was made by Kosaki-san.

> On 32 bit x86, the effective vmalloc space is 64Mb or so (after various PCI bars are ioremaped),
> so if this type of allocation is used for a "scales with nr of ABC" where "ABC" is workload dependent,
> there's a rather abrupt upper limit to this.
> Not saying that that is a flaw of your patch, just pointing out that we should discourage usage of 
> the "scales with nr of ABC" (for example "one for each thread") kind of things.

I better take out any patches that do large scale allocs then.
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