From: Peter Zijlstra <peterz@infradead.org>
To: Joel Schopp <jschopp@austin.ibm.com>
Cc: Michael Neuling <mikey@neuling.org>,
ego@in.ibm.com, linuxppc-dev@lists.ozlabs.org,
Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCHv4 2/2] powerpc: implement arch_scale_smt_power for Power7
Date: Thu, 18 Feb 2010 18:08:04 +0100 [thread overview]
Message-ID: <1266512884.26719.869.camel@laptop> (raw)
In-Reply-To: <4B7D6AAB.5080602@austin.ibm.com>
On Thu, 2010-02-18 at 10:28 -0600, Joel Schopp wrote:
> > There's one fundamental assumption, and one weakness in the
> > implementation.
> >
> I'm going to guess the weakness is that it doesn't adjust the cpu power
> so tasks running in SMT1 mode actually get more than they account for?
No, but you're right, if these SMTx modes are running at different
frequencies then yes that needs to happen as well.
The weakness is failing to do the right thing in the presence of a
'strategically' placed RT task.
Suppose:
Sibling0, Sibling1, Sibling2, Sibling3
idle OTHER OTHER FIFO
it might not manage to migrate a task to 0 because it ends up selecting
3 as busiest. It doesn't at all influence RT placement, but it does look
at nr_running (which does include RT tasks)
> What's the assumption?
That cpu_of(Sibling n) < cpu_of(Sibling n+1)
next prev parent reply other threads:[~2010-02-18 17:08 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-20 20:00 [PATCH 0/2] sched: arch_scale_smt_powers Joel Schopp
2010-01-20 20:02 ` [PATCH 1/2] sched: Fix the place where group powers are updated Joel Schopp
2010-01-26 23:28 ` [PATCHv2 1/2] sched: enable ARCH_POWER Joel Schopp
2010-01-28 23:20 ` [PATCHv3 " Joel Schopp
2010-02-05 20:57 ` [PATCHv4 " Joel Schopp
2010-01-20 20:04 ` [PATCH 2/2] powerpc: implement arch_scale_smt_power for Power7 Joel Schopp
2010-01-20 20:48 ` Peter Zijlstra
2010-01-20 21:58 ` Michael Neuling
2010-01-20 22:44 ` Joel Schopp
2010-01-21 8:27 ` Peter Zijlstra
2010-01-20 21:04 ` Michael Neuling
2010-01-20 22:09 ` Joel Schopp
2010-01-24 3:00 ` Benjamin Herrenschmidt
2010-01-25 17:50 ` Joel Schopp
2010-01-26 4:23 ` Benjamin Herrenschmidt
2010-01-20 21:33 ` Benjamin Herrenschmidt
2010-01-20 22:36 ` Joel Schopp
2010-01-26 23:28 ` [PATCHv2 " Joel Schopp
2010-01-27 0:52 ` Benjamin Herrenschmidt
2010-01-28 22:39 ` Joel Schopp
2010-01-29 1:23 ` Benjamin Herrenschmidt
2010-01-28 23:20 ` [PATCHv3 " Joel Schopp
2010-01-28 23:24 ` Joel Schopp
2010-01-29 1:23 ` Benjamin Herrenschmidt
2010-01-29 10:13 ` Peter Zijlstra
2010-01-29 18:34 ` Joel Schopp
2010-01-29 18:41 ` Joel Schopp
2010-02-05 20:57 ` [PATCHv4 " Joel Schopp
2010-02-14 10:12 ` Peter Zijlstra
2010-02-17 22:20 ` Michael Neuling
2010-02-18 13:17 ` Peter Zijlstra
2010-02-18 13:19 ` Peter Zijlstra
2010-02-18 16:28 ` Joel Schopp
2010-02-18 17:08 ` Peter Zijlstra [this message]
2010-02-19 6:05 ` Michael Neuling
2010-02-19 10:01 ` Peter Zijlstra
2010-02-19 11:01 ` Michael Neuling
2010-02-23 6:08 ` Michael Neuling
2010-02-23 16:24 ` Peter Zijlstra
2010-02-23 16:30 ` Peter Zijlstra
2010-02-24 6:07 ` Michael Neuling
2010-02-24 11:13 ` Michael Neuling
2010-02-24 11:58 ` Michael Neuling
2010-02-27 10:21 ` Michael Neuling
2010-03-02 14:44 ` Peter Zijlstra
2010-03-04 22:28 ` Michael Neuling
2010-01-29 12:25 ` [PATCHv3 " Gabriel Paubert
2010-01-29 16:26 ` Joel Schopp
2010-01-26 23:27 ` [PATCHv2 0/2] sched: arch_scale_smt_powers v2 Joel Schopp
2010-01-28 23:20 ` [PATCHv3 0/2] sched: arch_scale_smt_powers Joel Schopp
2010-02-05 20:57 ` [PATCHv4 " Joel Schopp
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=1266512884.26719.869.camel@laptop \
--to=peterz@infradead.org \
--cc=ego@in.ibm.com \
--cc=jschopp@austin.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mikey@neuling.org \
--cc=mingo@elte.hu \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).