linux-kernel - Re: soft lockup - CPU#1 stuck for 15s! [swapper:0]

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Date:	Fri, 14 Dec 2007 19:51:28 -0500
From:	"Parag Warudkar" <parag.warudkar@...il.com>
To:	"Len Brown" <lenb@...nel.org>
Cc:	"Thomas Gleixner" <tglx@...utronix.de>,
	"Arjan van de Ven" <arjan@...radead.org>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>
Subject: Re: soft lockup - CPU#1 stuck for 15s! [swapper:0]

On Dec 14, 2007 6:17 PM, Len Brown <lenb@...nel.org> wrote:
> does processor.max_cstate=1 make the failing configuration work?
> If yes, how about processor.max_cstate=2?

Until now 2 things were necessary to reproduce the problem -
1) CPU_IDLE=y and
2) Wakeups from Idle = 5-7 Per second (== Longer/deeper C state residency)

If I left the wakeups to high number (50-60) - there were no lockups
but it was very jerky over ssh.
(Typing keys had no effect for seconds etc.)

CPU_IDLE=y

With max_cstate=1 and CPU_IDLE=y things are pretty smooth - no lockups
for the last hour. (Soft lockups used to appear in minutes
previously.)

With max_cstate=2 - old story repeats - it's very jerky and soft
lockups appear in under a minute after going to 3-5 wakeups from idle
per sec.

>
> what do you see in /proc/acpi/processor/*/power?
>

Normally (without any max_cstate= parameter) I see this -
(I admit I never thought there was a C8 - C3 was all I ever heard.)

[parag@...i router]$ cat /proc/acpi/processor/CPU0/power
active state:            C2
max_cstate:              C8
bus master activity:     00000000
maximum allowed latency: 8000 usec
states:
    C1:                  type[C1] promotion[C2] demotion[--]
latency[001] usage[00001010] duration[00000000000000000000]
   *C2:                  type[C2] promotion[--] demotion[C1]
latency[001] usage[07181700] duration[00000000379397304978]


Thanks
Parag
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