[Xen-devel] RE: [Xen-changelog] [xen-unstable] [PV-ON-HVM] Don't generate lots ofspurious interrupts when using event

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

>From: Steven Smith
>Sent: 2006年11月2日 19:38
>
>>      This does solve the problem, however it adds unnecessary
>overhead
>> (one more trap into xen at the end of each event handler). IMO, the
>real
>> cause should be in pic_intack, where pending irr is converted into isr.
>I'm inclined to agree here.  The patch I checked in certainly wasn't
>very pretty, and this is the best alternative I've heard so far.
>However, it looks like it's actually slower than what we've got at the
>moment: NPtcp between dom0 and domU on my test box reports a
>latency
>and maximum bandwidth of 36.42us and 1961.58Mbps without this
>patch, or
>45.94us and 1874.69Mbps with.  All measurements are best-of-three.
>
>Looking at the patch, it ought to have been slightly faster, so these
>results rather surprised me.  Did you do any benchmarks yourself?
>
>Steven.

No, I didn't because when I reading your patch it simply indicated a 
spurious interrupt issue to be fixed there. Based on the description, 
I came up above as an alternative. It's quite interesting to see such fix 
with so obvious performance degradation. BTW, is it a typo? This logic 
should only matter for hvm guest, and why throughout between dom0 
and domU is affected which is more odd if true?

Thanks,
Kevin

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