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RE: single software TLB vs. multiple software TLBs (was RE: [Xen-ia64-devel] [PATCH] [Resend]Enable hash vtlb)


  • To: <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Dong, Eddie" <eddie.dong@xxxxxxxxx>
  • Date: Thu, 13 Apr 2006 20:20:14 +0800
  • Delivery-date: Thu, 13 Apr 2006 05:20:32 -0700
  • List-id: Discussion of the ia64 port of Xen <xen-ia64-devel.lists.xensource.com>
  • Thread-index: AcZeQwzGkG/7QGfmRJiAmulTDR9D4QAr6vLg
  • Thread-topic: single software TLB vs. multiple software TLBs (was RE: [Xen-ia64-devel] [PATCH] [Resend]Enable hash vtlb)

Alex:
     It becomes much clear now that multiple softsware TLB support is a must in 
functionality. For at least following reasons:
        1: We should merge VTI and para domain vMMU code together to reduce 
future maintaince effort. In this case multiple software TLB support for MMIOs 
is a must for VTI domain and thus a must for Xen/IA64.
        2: Para domain needs to capture guest MMIO access too in case a native 
driver in guest detect its existance. Definitely we should not crash system in 
that case, so multiple software TLB support is a must too.
        3: Multiple software TLBs provides flexibility for guest huge TLB 
translations.

        Anthony's patch is ready to support all of above as a functionality 
ready solution, and so far I didn't see anybody against multiple software TLB 
support. Can u check in now as a build option? The performance difference in 
1-2 percent should be a second level consideration for now.

Thanks very much!
Eddie


Tristan Gingold wrote:
> Le Mercredi 12 Avril 2006 16:51, Dong, Eddie a écrit :
>> Tristan Gingold wrote:
>> At every tlb miss time, you can get guest translation from software
>> TLB (not from VHPT). You actually don't need to care about VHPT
>> entries no matter it is all there or nothing there.
> Ok, it is clear now.
> 
> Tristan.

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