From mboxrd@z Thu Jan  1 00:00:00 1970
From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Subject: Re: [PATCH] vhost: try to shrink pfdset when fdset_add
	fails
Date: Wed, 22 Feb 2017 09:59:31 +0800
Message-ID: <20170222015931.GK18844@yliu-dev.sh.intel.com>
References: <20170221142530.31472-1-matthias.gatto@outscale.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: dev@dpdk.org
To: Matthias Gatto <matthias.gatto@outscale.com>
Return-path: <dev-bounces@dpdk.org>
Received: from mga01.intel.com (mga01.intel.com [192.55.52.88])
 by dpdk.org (Postfix) with ESMTP id E0B322A5E
 for <dev@dpdk.org>; Wed, 22 Feb 2017 02:57:10 +0100 (CET)
Content-Disposition: inline
In-Reply-To: <20170221142530.31472-1-matthias.gatto@outscale.com>
List-Id: DPDK patches and discussions <dev.dpdk.org>
List-Unsubscribe: <http://dpdk.org/ml/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://dpdk.org/ml/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <http://dpdk.org/ml/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org
Sender: "dev" <dev-bounces@dpdk.org>

On Tue, Feb 21, 2017 at 03:25:30PM +0100, Matthias Gatto wrote:
> fdset_add increment pfdset->num, but fdset_del doesn't decrement pfdset->num,
> so if we call fdset_add then fdset_del in a loop witout calling
> fdset_shrink, we can easily exceed MAX_FDS with only a few number of fds
> used.

I'm assuming you were doing some tests like following?

	while true; do
		ovs-vsctl add-port br vhost_n -- ...
		ovs-vsctl del-port vhost_n
	done

> So my solution is simply to call fdset_shrink in fdset_add
> when it exceed MAX_FDS.
> 
> Because fdset_shrink and fdset_add locks pfdset->fd_mutex we can't call
> fdset_shrink inside fdset_add because that would cause a dead lock,
> so this patch split fdset_shrink in two, fdset_shrink amd fdset_shrink_nolock.

Looks good to me.

	--yliu