From: Asias He <asias.hejun@gmail.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
Rusty Russell <rusty@rustcorp.com.au>,
Mark McLoughlin <markmc@redhat.com>,
Anthony Liguori <aliguori@us.ibm.com>,
Pekka Enberg <penberg@kernel.org>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Sasha Levin <levinsasha928@gmail.com>,
Prasad Joshi <prasadjoshi124@gmail.com>,
kvm@vger.kernel.org
Subject: Re: [PATCH 1/2] kvm tools: Respect ISR status in virtio header
Date: Sat, 07 May 2011 22:24:16 +0800 [thread overview]
Message-ID: <4DC55610.8070804@gmail.com> (raw)
In-Reply-To: <20110507140030.GA2859@elte.hu>
On 05/07/2011 10:00 PM, Ingo Molnar wrote:
>
> * Asias He <asias.hejun@gmail.com> wrote:
>
>> BTW. The ping latency was caused by the movement of irq injection outside the
>> loop. Suppose we have 5 available buffers and only 1 buffer from tap device.
>> We will sleep on read without giving the buffer from tap to guest. The
>> latency will be huge in this case.
>>
>> while(virt_queue__available(vq)) {
>> ...
>> read(tap_fd)
>> ...
>> }
>> trigger_irq()
>
> But ... in one of the mails one of you claimed that even when moving the irq
> notification inside the loop (which we all agreed was necessary to avoid
> latencies!) the latencies would still occur during stress-tests.
What I got in stress-tests(ping -f) with irq notification inside the
loop is only network hangs.
>
> So something is still not understood here and could hit us anytime with any of
> the virtio drivers in the future and such bugs are not always so nice to debug
> like the latency problem here ...
Yes, Especially when they are under tremendous stress.
>
> Thanks,
>
> Ingo
>
--
Best Regards,
Asias He
next prev parent reply other threads:[~2011-05-07 14:25 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-07 2:34 [PATCH 1/2] kvm tools: Respect ISR status in virtio header Asias He
2011-05-07 2:34 ` [PATCH 2/2] kvm tools: Respect VRING_AVAIL_F_NO_INTERRUPT Asias He
2011-05-07 7:55 ` Ingo Molnar
2011-05-07 9:03 ` Pekka Enberg
2011-05-07 11:25 ` Asias He
2011-05-07 9:30 ` [PATCH 1/2] kvm tools: Respect ISR status in virtio header Ingo Molnar
2011-05-07 10:34 ` Sasha Levin
2011-05-07 10:39 ` Pekka Enberg
2011-05-07 10:39 ` Asias He
2011-05-07 11:15 ` Asias He
2011-05-07 14:00 ` Ingo Molnar
2011-05-07 14:24 ` Asias He [this message]
2011-05-07 13:14 ` Anthony Liguori
2011-05-07 14:02 ` Ingo Molnar
2011-05-07 14:21 ` Anthony Liguori
2011-05-07 14:47 ` Ingo Molnar
2011-05-07 14:52 ` Pekka Enberg
2011-05-07 14:55 ` Ingo Molnar
2011-05-07 14:50 ` Pekka Enberg
2011-05-07 15:01 ` Anthony Liguori
2011-05-07 15:02 ` Pekka Enberg
2011-05-07 15:06 ` Ingo Molnar
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