From: Andi Kleen <andi@firstfloor.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Friesen <cfriesen@nortel.com>, Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Steven Rostedt <rostedt@goodmis.org>,
David Miller <davem@davemloft.net>,
linuxppc-dev@ozlabs.org, paulus@samba.org,
netdev@vger.kernel.org
Subject: Re: question about softirqs
Date: Wed, 13 May 2009 16:24:23 +0200 [thread overview]
Message-ID: <87my9hkrmw.fsf@basil.nowhere.org> (raw)
In-Reply-To: <alpine.LFD.2.00.0905131612180.3561@localhost.localdomain> (Thomas Gleixner's message of "Wed, 13 May 2009 16:17:08 +0200 (CEST)")
Thomas Gleixner <tglx@linutronix.de> writes:
> Err, no. Chris is completely correct:
>
> if (!in_interrupt())
> wakeup_softirqd();
Yes you have to wake it up just in case, but it doesn't normally
process the data because a normal softirq comes in faster. It's
just a safety policy.
You can check this by checking the accumulated CPU time on your
ksoftirqs. Mine are all 0 even on long running systems.
The reason Andrea originally added the softirqds was just that
if you have very softirq intensive workloads they would tie
up too much CPU time or not make enough process with the default
"don't loop too often" heuristics.
> We can not rely on irqs coming in when the softirq is raised from
You can't rely on it, but it happens in near all cases.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2009-05-13 14:24 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <18948.63755.279732.294842@cargo.ozlabs.ibm.com>
[not found] ` <20090508.234815.127227651.davem@davemloft.net>
[not found] ` <4A086DB2.8040703@nortel.com>
[not found] ` <20090511.162436.193717082.davem@davemloft.net>
2009-05-12 0:43 ` question about softirqs Chris Friesen
2009-05-12 8:12 ` Ingo Molnar
2009-05-12 9:12 ` Peter Zijlstra
2009-05-12 9:23 ` Ingo Molnar
2009-05-12 9:32 ` Peter Zijlstra
2009-05-12 12:20 ` Steven Rostedt
2009-05-13 4:45 ` David Miller
2009-05-13 4:44 ` David Miller
2009-05-13 5:15 ` Paul Mackerras
2009-05-13 5:28 ` David Miller
2009-05-13 5:55 ` Evgeniy Polyakov
2009-05-12 15:18 ` Chris Friesen
2009-05-13 8:34 ` Andi Kleen
2009-05-13 13:23 ` Chris Friesen
2009-05-13 14:15 ` Andi Kleen
2009-05-13 14:17 ` Thomas Gleixner
2009-05-13 14:24 ` Andi Kleen [this message]
2009-05-13 14:54 ` Eric Dumazet
2009-05-13 15:02 ` Andi Kleen
2009-05-13 15:05 ` Chris Friesen
2009-05-13 15:54 ` Thomas Gleixner
2009-05-13 16:10 ` Chris Friesen
2009-05-13 17:01 ` Andi Kleen
2009-05-13 19:04 ` Chris Friesen
2009-05-13 19:13 ` Andi Kleen
2009-05-13 19:44 ` Chris Friesen
2009-05-13 19:53 ` Andi Kleen
2009-05-13 20:55 ` Thomas Gleixner
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