From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [RFC PATCH] kick ksoftirqd more often to please soft lockup detector Date: Wed, 29 Feb 2012 10:17:03 +0100 Message-ID: <1330507023.11248.113.camel@twins> References: <20120227203847.22153.62468.stgit@dwillia2-linux.jf.intel.com> <1330422535.11248.78.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Dan Williams Cc: Thomas Gleixner , linux-kernel@vger.kernel.org, Jens Axboe , linux-scsi@vger.kernel.org, Lukasz Dorau , James Bottomley , Andrzej Jakowski List-Id: linux-scsi@vger.kernel.org On Tue, 2012-02-28 at 14:16 -0800, Dan Williams wrote: > Looks like everyone is guilty: > > [ 422.765336] softirq took longer than 1/4 tick: 3 NET_RX ffffffff813f0aa0 > ... > [ 423.971878] softirq took longer than 1/4 tick: 4 BLOCK ffffffff812519c8 > [ 423.985093] softirq took longer than 1/4 tick: 6 TASKLET ffffffff8103422e > [ 423.993157] softirq took longer than 1/4 tick: 7 SCHED ffffffff8105e2e1 > [ 424.001018] softirq took longer than 1/4 tick: 9 RCU ffffffff810a0fed > [ 424.008691] softirq loop took longer than 1/2 tick need_resched: /me kicks himself for not printing the actual duration.. :-) > As expected whenever that 1/2 tick message gets emitted the softirq > handler is almost running in a need_resched() context. Yeah.. that's quite expected. > So is it a good idea to get more aggressive about scheduling ksoftrrqd? Nah, moving away from softirq more like. I'll put moving the load-balancer into a kthread on the todo list. And it looks like everybody else should move to kthreads too.