From: Andi Kleen <andi@firstfloor.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Marcio Saito <marcio@cyclades.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Jiri Slaby <jirislaby@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
John Stultz <johnstul@us.ibm.com>,
x86@kernel.org, LKML <linux-kernel@vger.kernel.org>,
Tim Pepper <lnxninja@linux.vnet.ibm.com>,
jblunck@infradead.org, Ingo Molnar <mingo@redhat.com>,
Paul Mackerras <paulus@samba.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Avantika Mathur <mathur@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [RFC] [PATCH] allow low HZ values?
Date: Tue, 12 Oct 2010 16:31:20 +0200 [thread overview]
Message-ID: <871v7v32kn.fsf@basil.nowhere.org> (raw)
In-Reply-To: <alpine.LFD.2.00.1010112227190.2909@localhost6.localdomain6> (Thomas Gleixner's message of "Mon, 11 Oct 2010 22:32:06 +0200 (CEST)")
Thomas Gleixner <tglx@linutronix.de> writes:
> On Mon, 11 Oct 2010, Tim Pepper wrote:
>
>> I'm not necessarily wanting to open up the age old question of "what is
>> a good HZ", but we were doing some testing on timer tick overheads for
>> HPC applications and this came up...
>
> Yeah. This comes always up when the timer tick overhead on HPC is
> tested. And this patch is again the fundamentally wrong answer.
That's a unfair description of the proposal.
> We have told HPC folks for years that we need a kind of "NOHZ" mode
> for HPC where we can transparently switch off the tick when only one
> user space bound thread is active and switch back to normal once this
> thing terminates or goes into the kernel via a syscall. Sigh, nothing
> happened ever except for repeating the same crap patches over and
> over.
Jan Blunck posted a patch for this exactly few months ago.
Unfortunately it didn't get the accounting right, but other than
that it seemed like a reasonable starting point.
-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: Tim Pepper <lnxninja@linux.vnet.ibm.com>,
Marcio Saito <marcio@cyclades.com>,
John Stultz <johnstul@us.ibm.com>,
Jiri Slaby <jirislaby@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
x86@kernel.org, LKML <linux-kernel@vger.kernel.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@redhat.com>, Paul Mackerras <paulus@samba.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Avantika Mathur <mathur@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org, jblunck@infradead.org
Subject: Re: [RFC] [PATCH] allow low HZ values?
Date: Tue, 12 Oct 2010 16:31:20 +0200 [thread overview]
Message-ID: <871v7v32kn.fsf@basil.nowhere.org> (raw)
In-Reply-To: <alpine.LFD.2.00.1010112227190.2909@localhost6.localdomain6> (Thomas Gleixner's message of "Mon, 11 Oct 2010 22:32:06 +0200 (CEST)")
Thomas Gleixner <tglx@linutronix.de> writes:
> On Mon, 11 Oct 2010, Tim Pepper wrote:
>
>> I'm not necessarily wanting to open up the age old question of "what is
>> a good HZ", but we were doing some testing on timer tick overheads for
>> HPC applications and this came up...
>
> Yeah. This comes always up when the timer tick overhead on HPC is
> tested. And this patch is again the fundamentally wrong answer.
That's a unfair description of the proposal.
> We have told HPC folks for years that we need a kind of "NOHZ" mode
> for HPC where we can transparently switch off the tick when only one
> user space bound thread is active and switch back to normal once this
> thing terminates or goes into the kernel via a syscall. Sigh, nothing
> happened ever except for repeating the same crap patches over and
> over.
Jan Blunck posted a patch for this exactly few months ago.
Unfortunately it didn't get the accounting right, but other than
that it seemed like a reasonable starting point.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2010-10-12 15:03 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-11 20:11 [RFC] [PATCH] allow low HZ values? Tim Pepper
2010-10-11 20:11 ` Tim Pepper
2010-10-11 20:32 ` Thomas Gleixner
2010-10-11 20:32 ` Thomas Gleixner
2010-10-11 21:11 ` Tim Pepper
2010-10-11 21:11 ` Tim Pepper
2010-10-12 14:31 ` Andi Kleen [this message]
2010-10-12 14:31 ` Andi Kleen
2010-10-12 16:56 ` Thomas Gleixner
2010-10-12 16:56 ` Thomas Gleixner
2010-10-11 22:30 ` Benjamin Herrenschmidt
2010-10-11 22:30 ` Benjamin Herrenschmidt
2010-10-11 22:33 ` Thomas Gleixner
2010-10-11 22:33 ` Thomas Gleixner
2010-10-11 22:47 ` H. Peter Anvin
2010-10-11 22:47 ` H. Peter Anvin
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