On 08/23/2011 11:09 AM, Tian, Kevin wrote:
Hi, Avi,
Both Eddie and Marcello once suggested vEOI optimization by skipping
heavy-weight instruction decode, which reduces vEOI overhead greatly:
http://www.mail-archive.com/[email protected]/msg18619.html
http://www.spinics.net/lists/kvm/msg36691.html
Though virtual x2apic serves similar purpose, it depends on guest OS
to support x2apic. Many Windows versions don't support x2apic though,
including Win7, Windows server before 2008 R2, etc. Given that virtualization
need support various OS versions, any chance to incorporate above vEOI
optimization in KVM as an alternative to boost performance when guest
doesn't support x2apic?
Yes. There was a problem with the guest using MOVSD or STOSD to write
the EOI; if we don't emulate, then registers don't get updated. I guess
we can ignore it since no sane guest will use those instructions for EOI.
Another option is the hyper-V EOI support, which can also eliminate the
EOI exit when no additional interrupt is pending. This can improve EOI
performance even more.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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