Messages in this thread | | | Date | Mon, 18 Aug 2008 22:09:46 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [patch]pageattr: cache flush before tlb flush |
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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.
-hpa
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