From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 22 Sep 2001 16:56:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 22 Sep 2001 16:56:02 -0400 Received: from maile.telia.com ([194.22.190.16]:202 "EHLO maile.telia.com") by vger.kernel.org with ESMTP id ; Sat, 22 Sep 2001 16:55:53 -0400 Message-Id: <200109222056.f8MKu8K24322@maile.telia.com> Content-Type: text/plain; charset="iso-8859-1" From: Roger Larsson To: Andrea Arcangeli Subject: Re: ksoftirqd? (Was: Re: [PATCH] Preemption Latency Measurement Tool) Date: Sat, 22 Sep 2001 22:51:16 +0200 X-Mailer: KMail [version 1.3.1] Cc: Robert Love , Andre Pang , linux-kernel@vger.kernel.org, safemode@speakeasy.net, Dieter.Nuetzel@hamburg.de, iafilius@xs4all.nl, ilsensine@inwind.it, george@mvista.com In-Reply-To: <1000939458.3853.17.camel@phantasy> <200109221301.f8MD1n129687@mailc.telia.com> <20010922151453.B976@athlon.random> In-Reply-To: <20010922151453.B976@athlon.random> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Saturday 22 September 2001 15.14, Andrea Arcangeli wrote: > On Sat, Sep 22, 2001 at 02:56:58PM +0200, Roger Larsson wrote: > > Hi, > > > > We have a new kid on the block since we started thinking of a preemptive > > kernel. > > > > ksoftirqd... > > > > Running with nice 19 (shouldn't it really be -19?) I repeat this question - should it be nice 19 and not nice -19 (not nice)? > > Or have a RT setting? (maybe not since one of the reasons for > > softirqd would be lost - would be scheduled in immediately) > > Can't a high prio or RT process be starved due to missing > > service (bh) after an interrupt? > > It cannot be starved, if ksoftirqd is never scheduled the do_softirq() > will be run by the next timer irq or apic_timer irq. > Then could you please explain the output after adding a printk in ksoftirqd like this. --- kernel/softirq.c~ Mon Sep 17 22:37:34 2001 +++ kernel/softirq.c Sat Sep 22 21:46:49 2001 @@ -387,6 +387,7 @@ __set_current_state(TASK_RUNNING); while (softirq_pending(cpu)) { + printk("ksoftirqd: do_softirq\n"); do_softirq(); if (current->need_resched) schedule(); Output like this: Sep 22 22:37:38 jeloin logger: *** ./stress_dbench begin *** Sep 22 22:37:42 jeloin kernel: ksoftirqd: do_softirq Sep 22 22:37:44 jeloin last message repeated 2 times Sep 22 22:37:48 jeloin kernel: Latency 8ms PID 7 %% kupdated Sep 22 22:37:49 jeloin kernel: ksoftirqd: do_softirq Sep 22 22:38:19 jeloin last message repeated 18 times Sep 22 22:38:20 jeloin su: (to root) roger on /dev/pts/2 Sep 22 22:38:20 jeloin PAM-unix2[988]: session started for user root, service su Sep 22 22:38:23 jeloin kernel: ksoftirqd: do_softirq Sep 22 22:38:24 jeloin modprobe: modprobe: Can't locate module net-pf-10 Sep 22 22:38:24 jeloin kernel: ksoftirqd: do_softirq Sep 22 22:38:58 jeloin last message repeated 20 times Sep 22 22:39:05 jeloin last message repeated 4 times Sep 22 22:42:03 jeloin kernel: ksoftirqd: do_softirq Sep 22 22:43:58 jeloin logger: *** ./stress_dbench end *** > > This will not show up in latency profiling patches since > > the kernel does what is requested... > > > > Previously it was run directly after interrupt, > > before returning to the interrupted process... > > It is still the case, that's also the common case actually. > Possibly but the other case is quite common too... /RogerL -- Roger Larsson Skellefteċ Sweden