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From: Jamie Lokier <jamie@shareable.org>
To: "Richard W.M. Jones" <rjones@redhat.com>
Cc: qemu-devel@nongnu.org, David Ahern <dsahern@gmail.com>
Subject: Re: [Qemu-devel] PATCH: enabling TCP keepalives - v3
Date: Fri, 1 May 2009 13:23:37 +0100	[thread overview]
Message-ID: <20090501122337.GC15311@shareable.org> (raw)
In-Reply-To: <20090501113204.GA10763@amd.home.annexia.org>

Richard W.M. Jones wrote:
> On Thu, Apr 30, 2009 at 01:40:42PM -0600, David Ahern wrote:
> > Did not see a response to the last version.
> > 
> > This patch enables TCP keepalives on VNC connections and TCP-based char
> > devices.
> > 
> > Default parameters have keep alive probes sent after 60-seconds of idle
> > time. Probes are sent every 12 seconds with the connection resetting
> > after 5 failed probes (ie., connection is closed if no response received
> > in 60-seconds).
> 
> IMHO this should be optional, and firmly default to _OFF_.  Brief
> network outages shouldn't result in connections failing all over the
> place.  In addition, does this negatively impact migration?

Note that if either side tries to send actual data, such as due to a
mouse movement or screen update, then connections will fail after a
TCP timeout anyway.  There's no getting away from a network outage
tripping it, unless the session is completely idle - static screen, no
input.

Keepalive just causes the connections to drop when there was no other
traffic to detect the connection being down.  It's being added because
without it, QEMU accumulates connections when the network is really is
gone - they never go away.

-- Jamie

  reply	other threads:[~2009-05-01 12:23 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-04-30 19:40 [Qemu-devel] PATCH: enabling TCP keepalives - v3 David Ahern
2009-05-01 11:32 ` Richard W.M. Jones
2009-05-01 12:23   ` Jamie Lokier [this message]
2009-05-01 12:49   ` David Ahern
2009-05-01 15:23     ` Daniel P. Berrange
2009-05-01 15:47       ` David Ahern
2009-05-01 17:21         ` Richard W.M. Jones
2009-05-05  1:31         ` Jamie Lokier
2009-05-05  2:59           ` David Ahern
2009-05-01 15:52       ` Avi Kivity
2009-05-01 16:11         ` John Haxby
2009-05-05  1:35           ` Jamie Lokier
2009-05-01 14:43 ` Anthony Liguori
2009-05-01 14:47   ` David Ahern
2009-05-01 14:51     ` Anthony Liguori
2009-05-01 15:16       ` Paul Brook
2009-05-01 15:57         ` Anthony Liguori
2009-05-01 16:04           ` Paul Brook
2009-05-01 16:11             ` David Ahern

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