From: "Michael S. Tsirkin" <mst@redhat.com>
To: Kevin Wolf <kwolf@redhat.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>,
qemu-devel <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH] do not send packet to nic if the packet will be dropped by nic
Date: Mon, 20 Jun 2011 14:13:32 +0300 [thread overview]
Message-ID: <20110620111332.GA24344@redhat.com> (raw)
In-Reply-To: <4DFF1854.3070003@redhat.com>
On Mon, Jun 20, 2011 at 11:52:20AM +0200, Kevin Wolf wrote:
> Am 20.06.2011 11:40, schrieb Wen Congyang:
> > At 06/20/2011 05:10 PM, Kevin Wolf Write:
> >> Am 17.06.2011 03:33, schrieb Wen Congyang:
> >>> If !s->clock_enabled or !rtl8139_receiver_enabled(s), it means that
> >>> the nic will drop all packets from host. So qemu will keep getting
> >>> packets from host and wasting CPU on dropping packets. This seems
> >>> worse than packets that should be dropped but aren't.
> >>>
> >>> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
> >>
> >> Which bug does this change fix? I'm still not convinced that we should
> >> do it.
> >
> > Maybe not a bug fix now. As Michael S. Tsirkin said, if rtl8139_can_receive()
> > returns 1, qemu will keep getting packets from host and wasting CPU on
> > dropping packets. We can save CPU by return 0.
>
> Don't we waste memory instead then because we leave the packets queued
> indefinitely?
>
> Kevin
Yes but the amount of wasted memory is bound from above
so this doesn't seem too bad to me ...
--
MST
next prev parent reply other threads:[~2011-06-20 11:13 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-16 8:23 [Qemu-devel] [PATCH] fix the return value of rtl8139_can_receive() Wen Congyang
2011-06-16 10:39 ` Kevin Wolf
2011-06-16 12:46 ` Michael S. Tsirkin
2011-06-17 1:33 ` [Qemu-devel] [PATCH] do not send packet to nic if the packet will be dropped by nic Wen Congyang
2011-06-20 9:10 ` Kevin Wolf
2011-06-20 9:40 ` Wen Congyang
2011-06-20 9:52 ` Kevin Wolf
2011-06-20 11:13 ` Michael S. Tsirkin [this message]
2011-06-17 1:49 ` [Qemu-devel] [PATCH] fix the return value of rtl8139_can_receive() Wen Congyang
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