From patchwork Sat Oct 24 04:35:53 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Eric Dumazet X-Patchwork-Id: 36828 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.176.167]) by ozlabs.org (Postfix) with ESMTP id D1F81B7BC2 for ; Sat, 24 Oct 2009 15:37:14 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751541AbZJXEf5 (ORCPT ); Sat, 24 Oct 2009 00:35:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751376AbZJXEf5 (ORCPT ); Sat, 24 Oct 2009 00:35:57 -0400 Received: from gw1.cosmosbay.com ([212.99.114.194]:57774 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751082AbZJXEf5 (ORCPT ); Sat, 24 Oct 2009 00:35:57 -0400 Received: from [127.0.0.1] (localhost [127.0.0.1]) by gw1.cosmosbay.com (8.13.7/8.13.7) with ESMTP id n9O4Zs9r001092; Sat, 24 Oct 2009 06:35:55 +0200 Message-ID: <4AE28429.6040608@gmail.com> Date: Sat, 24 Oct 2009 06:35:53 +0200 From: Eric Dumazet User-Agent: Thunderbird 2.0.0.23 (Windows/20090812) MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: Octavian Purdila , Benjamin LaHaise , netdev@vger.kernel.org, Cosmin Ratiu Subject: Re: [PATCH] net: allow netdev_wait_allrefs() to run faster References: <20091017221857.GG1925@kvack.org> <4ADB55BC.5020107@gmail.com> <20091018182144.GC23395@kvack.org> <200910211539.01824.opurdila@ixiacom.com> <4ADF2B57.4030708@gmail.com> <20091023211338.GA6145@linux.vnet.ibm.com> In-Reply-To: <20091023211338.GA6145@linux.vnet.ibm.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-1.6 (gw1.cosmosbay.com [0.0.0.0]); Sat, 24 Oct 2009 06:35:56 +0200 (CEST) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Paul E. McKenney a écrit : > On Wed, Oct 21, 2009 at 05:40:07PM +0200, Eric Dumazet wrote: >> [PATCH] net: allow netdev_wait_allrefs() to run faster >> >> netdev_wait_allrefs() waits that all references to a device vanishes. >> >> It currently uses a _very_ pessimistic 250 ms delay between each probe. >> Some users report that no more than 4 devices can be dismantled per second, >> this is a pretty serious problem for extreme setups. >> >> Most likely, references only wait for a rcu grace period that should come >> fast, so use a schedule_timeout_uninterruptible(1) to allow faster recovery. > > Is this a place where synchronize_rcu_expedited() is appropriate? > (It went in to 2.6.32-rc1.) > Thanks for the tip Paul I believe netdev_wait_allrefs() is not a perfect candidate, because synchronize_sched_expedited() seems really expensive. Maybe we could call it once only, if we had to call 1 times the jiffie delay ? --- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/net/core/dev.c b/net/core/dev.c index fa88dcd..9b04b9a 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4970,6 +4970,7 @@ EXPORT_SYMBOL(register_netdev); static void netdev_wait_allrefs(struct net_device *dev) { unsigned long rebroadcast_time, warning_time; + unsigned int count = 0; rebroadcast_time = warning_time = jiffies; while (atomic_read(&dev->refcnt) != 0) { @@ -4995,7 +4996,10 @@ static void netdev_wait_allrefs(struct net_device *dev) rebroadcast_time = jiffies; } - msleep(250); + if (count++ == 1) + synchronize_rcu_expedited(); + else + schedule_timeout_uninterruptible(1); if (time_after(jiffies, warning_time + 10 * HZ)) { printk(KERN_EMERG "unregister_netdevice: "