From: Avi Kivity <avi@redhat.com>
To: Stefan Bader <stefan.bader@canonical.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@elte.hu>, Yinghai Lu <yinghai@kernel.org>,
Tejun Heo <tj@kernel.org>
Subject: Re: x86/mm: Limit 2/4M size calculation to x86_32
Date: Wed, 25 Jul 2012 16:40:55 +0300 [thread overview]
Message-ID: <500FF767.8020507@redhat.com> (raw)
In-Reply-To: <500FF3A1.6080809@canonical.com>
On 07/25/2012 04:24 PM, Stefan Bader wrote:
>>> ...
>>> ifdef CONFIG_X86_32
>>> /*
>>> * Don't use a large page for the first 2/4MB of memory
>>> * because there are often fixed size MTRRs in there
>>> * and overlapping MTRRs into large pages can cause
>>> * slowdowns.
>>> */
>>>
>>
>> That's equally true for X86_64.
>>
>> Best would be to merge the MTRRs into PAT, but that might not work for SMM.
>>
>>
> Ok, true. Not sure why this was restricted to 32bit when reconsidering. Except
> if in 64bit it was assumed (or asserted) that the regions are aligned to 2M...
> But maybe this can be answered by someone knowing the details. I would not mind
> either way (have the first range with 4K pages in all cases or fixing the
> additional PTE allocation). Just as it is now it is inconsistent.
Sometimes CONFIG_X86_32 is used as an alias for "machines so old they
don't support x86_64". As a 32-bit kernel can be run on a machine that
does support x86_64, it should be replaced by a runtime test for
X86_FEATURE_LM, until a more accurate test can be found.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2012-07-25 13:41 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-13 13:41 x86/mm: Limit 2/4M size calculation to x86_32 Stefan Bader
2012-07-13 18:12 ` Yinghai Lu
2012-07-15 19:09 ` Stefan Bader
2012-07-19 16:28 ` Stefan Bader
2012-07-24 15:52 ` Cong Wang
2012-07-25 10:44 ` Avi Kivity
2012-07-25 11:14 ` Stefan Bader
2012-07-25 12:32 ` Avi Kivity
2012-07-25 13:24 ` Stefan Bader
2012-07-25 13:40 ` Avi Kivity [this message]
2012-07-31 9:48 ` Stefan Bader
2012-07-31 10:07 ` Avi Kivity
2012-08-31 16:31 ` [PATCH] " Stefan Bader
2012-08-31 16:41 ` H. Peter Anvin
2012-08-31 16:56 ` Stefan Bader
2012-09-07 11:12 ` Stefan Bader
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