Message-Id: <478B29BE.76E4.0078.0@novell.com>
Date: Mon, 14 Jan 2008 08:22:06 +0000
From: "Jan Beulich" <jbeulich@novell.com>
To: "Jeremy Fitzhardinge" <Jeremy.Fitzhardinge@citrix.com>
Cc: "Ingo Molnar" <mingo@elte.hu>, <linux-kernel@vger.kernel.org>,
       "Jeremy Fitzhardinge" <jeremy@xensource.com>
Subject: Re: [PATCH] adjust/fix LDT handling for Xen
References: <4787436E.76E4.0078.0@novell.com> <4787A72E.8060704@citrix.com>
In-Reply-To: <4787A72E.8060704@citrix.com>
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>>> Jeremy Fitzhardinge <Jeremy.Fitzhardinge@citrix.com> 11.01.08 18:28 >>>
>Jan Beulich wrote:
>> Don't rely on kmalloc(PAGE_SIZE) returning PAGE_SIZE aligned memory
>> (Xen requires GDT *and* LDT to be page-aligned).
>
>Can kmalloc return non-page-aligned PAGE_SIZE allocations?

Documentation says it's to return pointer-size aligned memory - any excess
alignment is therefore an implementation detail. (Nevertheless, afaics all
current allocators generate page-aligned chunks.)

>>  Using the page
>> allocator interface also removes the (albeit small) slab allocator
>> overhead.
>
>Runtime or space overhead?  Given that they're once-off allocations, the 
>time part isn't a big factor.  And apparently LDT is completely unused.

Both, but as I also said the saving is small.

Jan

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