lkml.org 
[lkml]   [2008]   [Aug]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRE: [patch]pageattr: cache flush before tlb flush


>-----Original Message-----
>From: H. Peter Anvin [mailto:hpa@zytor.com]
>Sent: Tuesday, August 19, 2008 1:10 PM
>To: Li, Shaohua
>Cc: lkml; Andrew Morton; Ingo Molnar; Pallipadi, Venkatesh
>Subject: Re: [patch]pageattr: cache flush before tlb flush
>
>Shaohua Li wrote:
>> clflush uses a virtual address but cache line is physical indexed in
>> x86. In my understanding, clflush will do some pagetable walk, so doing
>> cache flush first should reduce some pagetable walk.
>>
>> Signed-off-by: Shaohua Li <shaohua.li@intel.com>
>
>I would say NAK on this.
>
>Doing the CLFLUSH first does cut down on page table walking, but opens a
>hole in the sequencing: first set PAT to an uncachable mode, then flush.
>
>If an unlucky prefetch comes in during this window, then you will have a
>dirty cache again.
>
>So no, this is not a good idea.
Ok, looks possible in theory.

Thanks,
Shaohua


\
 
 \ /
  Last update: 2008-08-19 07:27    [W:0.045 / U:0.132 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site