From mboxrd@z Thu Jan 1 00:00:00 1970 From: Damien Wyart Subject: Re: [Bug #12650] Strange load average and ksoftirqd behavior with 2.6.29-rc2-git1 Date: Sun, 15 Feb 2009 11:34:45 +0100 Message-ID: <20090215103445.GA2335@localhost.localdomain> References: <20090215080941.GA2295@localhost.localdomain> <20090215090026.GA31147@elte.hu> <20090215095128.GA3234@localhost.localdomain> <20090215101351.GA23274@elte.hu> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20090215101351.GA23274-X9Un+BFzKDI@public.gmane.org> Sender: kernel-testers-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Ingo Molnar Cc: "Rafael J. Wysocki" , Linux Kernel Mailing List , Kernel Testers List * Ingo Molnar [2009-02-15 11:13]: > Note that if the box you test this on is multi-core or HT, then interpreting > traces is easier if there's just a single CPU to look at. In that case i'd > suggest to reproduce with just a single core, by turning the second one off: > echo 0 > /sys/devices/system/cpu/cpu1/online > Or, if the problem only occurs with two cpus, restrict tracing to CPU#1: > echo 2 > /debug/tracing/tracing_cpumask The box I test on is HT, so I tried the first suggestion and it made the problem much less visible (but not completely absent). So I used "echo 1 > /sys/devices/system/cpu/cpu1/online" to go back to HT mode and then it made the problem much more visible on CPU#1: ksoftirqd/1 is running a lot and ksoftirqd/0 is almost normal. The load average is about 0.80 and the total running time for ksoftirqd/1 is almost one minute (and I booted on rc5 ten minutes ago)! So I followed the tracing steps in the tutorial (with the 1 sec sleep), which gave me this: http://damien.wyart.free.fr/trace_2.6.29-rc5_ksoftirqd_prob.txt.gz As I will be away until tomorrow, I did this on vanilla rc5 to get something out today, and if tip is really needed, I will work on it tomorrow. But maybe this vanilla trace will be helpful to you... Do not hesitate to ask for further tests or info. -- Damien