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[Xen-devel] RE: [Xen-ia64-devel] flush_tlb_mask and grant_table on ia64

To: "Tristan Gingold" <Tristan.Gingold@xxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>, <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] RE: [Xen-ia64-devel] flush_tlb_mask and grant_table on ia64
From: "Xu, Anthony" <anthony.xu@xxxxxxxxx>
Date: Fri, 21 Apr 2006 15:27:12 +0800
Delivery-date: Fri, 21 Apr 2006 00:27:47 -0700
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Thread-index: AcZlFB+F73j1a2cKSKWn1Q0iuykglQAAEFkg
Thread-topic: [Xen-ia64-devel] flush_tlb_mask and grant_table on ia64
>From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx
>[mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Tristan
>Sent: 2006?4?21? 15:24
>To: xen-devel@xxxxxxxxxxxxxxxxxxx; xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
>Subject: [Xen-ia64-devel] flush_tlb_mask and grant_table on ia64
>on IA64 flushing the whole TLB is very expensive: this is a cpu tlb flush and
>clearing 16MB of memory (virtual tlb).
>However, flushing an address range is rather cheap.  Flushing an address range
>on every processors is also cheap (no IPI).
>Unfortunatly Xen common code flushes the whole TLB after unmapping grant

>Currently, this is not done on IA64 because domain_dirty_cpumask is never set
>We can flush TLB by range within destroy_grant_host_mapping.  But then we need
>to disable the flush_tlb_mask call.
>What is the best solution?
It depends on the coverage of VHPT and coverage of purged page.
Linux kernel also use this,
If coverage of purged page is less than a fixed value, 
flush TLB by range.
If coverage of purged page is larger than a fixed value,
Flush the whole TLB.

>Thank you for comments,
>Xen-ia64-devel mailing list

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