RE: [Xen-ia64-devel] [PATCH] per vcpu vhpt

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

Hi Yamahata,

Sorry for late response.
This is a great patch, 
1. This patch should alleviate pain from migration.
2. VTI-domain and domU now use the same TR number for VHPT mapping, there is 
one more TC available to use, and that's good.

A very small comment,
I noticed DomU still use VHPT_ADDR to map VHPT. While in function, for 
instance, __vhpt_flush, it uses __va(vhpt_maddr) to access VHPT,  because vhpt 
is allocated from dom heap, this may cause unnecessary tlb miss.
There are two natural options here.
1. If DomU use __va(vhpt_maddr) to map VHPT, the unnecessary tlb miss can be 
eliminated.
2. in function like __vhpt_flush, use VHPT_ADDR to access VHPT.

One more thinking is, seems we plan to expose p2m table to domU, in this case, 
if we use VHPT_ADDR to map VHPT, itc can be "emulated" inside domU, when domU 
want to insert a mapping, it can look up p2m for machine physical address, then 
insert the transferred mapping into VHPT directly.

BTW, this issue is not introduced by this patch; it has been there for long 
time.


Thanks,
Anthony


>-----Original Message-----
>From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx
>[mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Isaku Yamahata
>Sent: 2006年10月6日 17:14
>To: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
>Subject: [Xen-ia64-devel] [PATCH] per vcpu vhpt
>
>
>per vcpu vhpt
>implement per vcpu vhpt option. allocate VHPT per vcpu.
>added compile time option, xen_ia64_pervcpu_vhpt=y, to enable it.
>Its default is on.
>added xen boot time option, pervcpu_vhpt=0, to disable it.
>
>This patch focuses on vcpu migration between physical cpus
>becaseu vcpu is heavily migrated with credit scheduler.
>This patch tries to reduce vTLB flush when vcpu is migrated
>
>--
>yamahata

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