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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
Date: Mon, 14 Jan 2008 08:22:06 +0000	[thread overview]
Message-ID: <478B29BE.76E4.0078.0@novell.com> (raw)
In-Reply-To: <4787A72E.8060704@citrix.com>

>>> 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


  reply	other threads:[~2008-01-14  8:21 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-11  9:22 [PATCH] adjust/fix LDT handling for Xen Jan Beulich
2008-01-11  9:39 ` Jiri Slaby
2008-01-11 10:08   ` Jan Beulich
2008-01-11 17:28 ` Jeremy Fitzhardinge
2008-01-14  8:22   ` Jan Beulich [this message]
2008-01-14 15:48 ` Ingo Molnar
2008-01-14 16:06   ` Jan Beulich
2008-01-14 17:04     ` Jeremy Fitzhardinge
2008-01-15 13:24       ` Ingo Molnar
2008-01-15 21:47         ` Jeremy Fitzhardinge

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