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Re: [Qemu-devel] [PATCH] Tap: fix vcpu long time io blocking on tap
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH] Tap: fix vcpu long time io blocking on tap |
Date: |
Fri, 11 Jul 2014 15:04:13 +0200 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Fri, Jul 11, 2014 at 01:05:30AM +0000, Wangkai (Kevin,C) wrote:
> When used a tap as net driver for vm, if too many packets was delivered to
> the
> guest os via tap interface, the guest os will be blocked on io events for a
> long
> time, while tap driver was busying process packets.
>
> kvm vcpu thread block on io lock call trace:
> __lll_lock_wait
> _L_lock_1004
> __pthread_mutex_lock
> qemu_mutex_lock
> kvm_cpu_exec
> qemu_kvm_cpu_thread_fn
> start_thread
>
> qemu io thread call trace:
> ...
> qemu_net_queue_send
> tap_send
> qemu_iohandler_poll
> main_loop_wait
> main_loop
>
>
> I think the qemu io lock time should be as small as possible, and the io work
> slice should be limited at a particular ration or time.
>
> ---
> Signed-off-by: Wangkai <address@hidden>
How many packets are you seeing in a single tap_send() call?
Have you profiled the tap_send() code path? Maybe it is performing some
operation that is very slow.
By the way, if you want good performance you should use vhost_net
instead of userspace vhost_net. Userspace virtio-net is not very
optimized.
Stefan
pgpxa_moEUv5y.pgp
Description: PGP signature
- [Qemu-devel] [PATCH] Tap: fix vcpu long time io blocking on tap, Wangkai (Kevin,C), 2014/07/10
- Re: [Qemu-devel] [PATCH] Tap: fix vcpu long time io blocking on tap,
Stefan Hajnoczi <=
- Re: [Qemu-devel] [PATCH] Tap: fix vcpu long time io blocking on tap, Wangkai (Kevin,C), 2014/07/13
- Re: [Qemu-devel] [PATCH] Tap: fix vcpu long time io blocking on tap, Stefan Hajnoczi, 2014/07/14
- Re: [Qemu-devel] [PATCH] Tap: fix vcpu long time io blocking on tap, Wangkai (Kevin,C), 2014/07/14
- Re: [Qemu-devel] [PATCH] Tap: fix vcpu long time io blocking on tap, Stefan Hajnoczi, 2014/07/15
- Re: [Qemu-devel] [PATCH] Tap: fix vcpu long time io blocking on tap, Wangkai (Kevin,C), 2014/07/16
- Re: [Qemu-devel] [PATCH] Tap: fix vcpu long time io blocking on tap, Wangkai (Kevin,C), 2014/07/16
- Re: [Qemu-devel] [PATCH] Tap: fix vcpu long time io blocking on tap, Jason Wang, 2014/07/17
- Re: [Qemu-devel] [PATCH] Tap: fix vcpu long time io blocking on tap, Wangkai (Kevin,C), 2014/07/17
Re: [Qemu-devel] [PATCH] Tap: fix vcpu long time io blocking on tap, Stefan Hajnoczi, 2014/07/17