Re: [Qemu-devel] [PATCH v3 04/13] netmap: Drop netmap_can_send

From: Stefan Hajnoczi <stefanha@gmail.com>
To: Fam Zheng <famz@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
	qemu-block@nongnu.org, Juan Quintela <quintela@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	qemu-devel@nongnu.org, Vincenzo Maffione <v.maffione@gmail.com>,
	"Vassili Karpov (malc)" <av1474@comtv.ru>,
	Gerd Hoffmann <kraxel@redhat.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Amit Shah <amit.shah@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Giuseppe Lettieri <g.lettieri@iet.unipi.it>,
	Luigi Rizzo <rizzo@iet.unipi.it>
Subject: Re: [Qemu-devel] [PATCH v3 04/13] netmap: Drop netmap_can_send
Date: Tue, 19 May 2015 15:54:33 +0100	[thread overview]
Message-ID: <20150519145433.GJ9338@stefanha-thinkpad.redhat.com> (raw)
In-Reply-To: <1432032670-15124-5-git-send-email-famz@redhat.com>

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On Tue, May 19, 2015 at 10:51:01AM +0000, Fam Zheng wrote:
> This callback is called by main loop before polling s->fd, if it returns
> false, the fd will not be polled in this iteration.
> 
> This is redundant with checks inside read callback. After this patch,
> the data will be copied from s->fd to s->iov when it arrives. If the
> device can't receive, it will be queued to incoming_queue, and when the
> device status changes, this queue will be flushed.
> 
> Also remove the qemu_can_send_packet() check in netmap_send. If it's
> true, we are good; if it's false, the qemu_sendv_packet_async would
> return 0 and read poll will be disabled until netmap_send_completed is
> called.

This causes unbounded memory usage in QEMU because
qemu_net_queue_append_iov() does not drop packets when sent_cb != NULL.

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