linux-kernel - Re: [PATCH] xen: core dom0 support

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Date:	Mon, 2 Mar 2009 13:08:59 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Xen-devel <xen-devel@...ts.xensource.com>
Subject: Re: [PATCH] xen: core dom0 support


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Ingo Molnar wrote:
>> Personally i'd like to see a sufficient reply to the 
>> mmap-perf paravirt regressions pointed out by Nick and 
>> reproduced by myself as well. (They were in the 4-5% 
>> macro-performance range iirc, which is huge.)
>>
>> So i havent seen any real progress on reducing native kernel 
>> overhead with paravirt. Patches were sent but no measurements 
>> were done and it seemed to have all fizzled out while the 
>> dom0 patches are being pursued.
>>   
>
> Hm, I'm not sure what you want me to do here.  I sent out 
> patches, they got merged, I posted the results of my 
> measurements showing that the patches made a substantial 
> improvement.  I'd love to see confirmation from others that 
> the patches help them, but I don't think you can say I've been 
> unresponsive about this.

Have i missed a mail of yours perhaps? I dont have any track of 
you having posted mmap-perf perfcounters results. I grepped my 
mbox and the last mail i saw from you containing the string 
"mmap-perf" is from January 20, and it only includes my numbers.

What i'd expect you to do is to proactively measure the overhead 
of CONFIG_PARAVIRT overhead of the native kernel, and analyze 
and address the results. Not just minimalistically reply to my 
performance measurements - as that does not really scale in the 
long run.

	Ingo
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