linux-kernel - Re: [PATCH 06/10] x86: reduce memory and stack usage in intel

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Message-ID: <47EA87D8.8030305@zytor.com>
Date:	Wed, 26 Mar 2008 10:28:56 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Mike Travis <travis@....com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Andi Kleen <ak@...e.de>
Subject: Re: [PATCH 06/10] x86: reduce memory and stack usage in	intel_cacheinfo

Ingo Molnar wrote:
>> The main goal was to avoid allocating 4096 bytes when only 32 would do 
>> (characters needed to represent nr_cpu_ids cpus instead of NR_CPUS 
>> cpus.) But I'll look at cleaning it up a bit more.  It wouldn't have 
>> to be a function if CHUNKSZ in cpumask_scnprintf() were visible (or a 
>> non-changeable constant.)
> 
> well, do we care about allocating 4096 bytes, as long as we also free 
> it? It's not like we need to clear all the bytes or something. Am i 
> missing something here?

Well, 32 bytes fits on the stack, whereas 4096 bytes requires allocating 
a page -- which means either taking the risk of failing or blocking.  Of 
course, we're doing this for output, which has the same issue.

	-hpa
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