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.
WARNING: multiple messages have this Message-ID (diff)
From: Andi Kleen <andi@firstfloor.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
netdev@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>,
linuxppc-dev@ozlabs.org, paulus@samba.org,
Ingo Molnar <mingo@elte.hu>, David Miller <davem@davemloft.net>
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: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-08 22:51 question about softirqs Chris Friesen
2009-05-08 23:05 ` David Miller
2009-05-08 23:34 ` Paul Mackerras
2009-05-08 23:53 ` David Miller
2009-05-09 2:52 ` Benjamin Herrenschmidt
2009-05-09 3:31 ` Paul Mackerras
2009-05-09 6:48 ` David Miller
2009-05-11 18:25 ` Chris Friesen
2009-05-11 23:24 ` David Miller
2009-05-12 0:43 ` Chris Friesen
2009-05-12 8:12 ` Ingo Molnar
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
2009-05-12 12:20 ` Steven Rostedt
2009-05-13 4:45 ` David Miller
2009-05-13 4:44 ` David Miller
2009-05-13 4:44 ` David Miller
2009-05-13 5:15 ` Paul Mackerras
2009-05-13 5:15 ` Paul Mackerras
2009-05-13 5:28 ` David Miller
2009-05-13 5:28 ` David Miller
2009-05-13 5:55 ` Evgeniy Polyakov
2009-05-13 5:55 ` Evgeniy Polyakov
2009-05-12 15:18 ` Chris Friesen
2009-05-12 15:18 ` Chris Friesen
2009-05-13 8:34 ` Andi Kleen
2009-05-13 8:34 ` Andi Kleen
2009-05-13 13:23 ` Chris Friesen
2009-05-13 14:15 ` Andi Kleen
2009-05-13 14:15 ` Andi Kleen
2009-05-13 14:17 ` Thomas Gleixner
2009-05-13 14:17 ` Thomas Gleixner
2009-05-13 14:24 ` Andi Kleen [this message]
2009-05-13 14:24 ` Andi Kleen
2009-05-13 14:54 ` Eric Dumazet
2009-05-13 14:54 ` Eric Dumazet
2009-05-13 15:02 ` Andi Kleen
2009-05-13 15:02 ` Andi Kleen
2009-05-13 15:05 ` Chris Friesen
2009-05-13 15:54 ` Thomas Gleixner
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 19:04 ` Chris Friesen
2009-05-13 19:13 ` Andi Kleen
2009-05-13 19:13 ` Andi Kleen
2009-05-13 19:44 ` Chris Friesen
2009-05-13 19:53 ` Andi Kleen
2009-05-13 19:53 ` Andi Kleen
2009-05-13 20:55 ` Thomas Gleixner
2009-05-13 20:55 ` Thomas Gleixner
2009-05-11 23:34 ` Paul Mackerras
2009-05-09 0:28 ` Chris Friesen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87my9hkrmw.fsf@basil.nowhere.org \
--to=andi@firstfloor.org \
--cc=a.p.zijlstra@chello.nl \
--cc=cfriesen@nortel.com \
--cc=davem@davemloft.net \
--cc=linuxppc-dev@ozlabs.org \
--cc=mingo@elte.hu \
--cc=netdev@vger.kernel.org \
--cc=paulus@samba.org \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.