From: Andrew Morton <akpm@osdl.org>
To: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: suresh.b.siddha@intel.com, mingo@elte.hu,
nickpiggin@yahoo.com.au, ak@suse.de,
linux-kernel@vger.kernel.org, rohit.seth@intel.com,
asit.k.mallick@intel.com
Subject: Re: [Patch] sched: new sched domain for representing multi-core
Date: Tue, 31 Jan 2006 18:21:36 -0800 [thread overview]
Message-ID: <20060131182136.665c8fe3.akpm@osdl.org> (raw)
In-Reply-To: <20060131174820.A32626@unix-os.sc.intel.com>
"Siddha, Suresh B" <suresh.b.siddha@intel.com> wrote:
>
> On Tue, Jan 31, 2006 at 05:12:16PM -0800, Andrew Morton wrote:
> > It's still not clear what's supposed to be happening here.
> >
> > In build_sched_domains() we still have code which does:
> >
> >
> > for_each_cpu_mask(...) {
> > ...
> > #ifdef CONFIG_SCHED_MC
> > ...
> > #endif
> > #ifdef CONFIG_SCHED_SMT
> > ...
> > #endif
> > ...
> > }
> > ...
> > #ifdef CONFIG_SCHED_SMT
> > ...
> > #endif
> > ...
> > #ifdef CONFIG_SCHED_MC
> > ...
> > #endif
> >
> > So in the first case the SCHED_SMT code will win and in the second case the
> > SCHED_MC code will win. I think.
>
> I am not sure what you mean here. At all the above pointed places, both
> MC and SMT will win if both are configured.
I was assuming that the code really does something like:
#ifdef CONFIG_SCHED_MC
some_global_thing = <expr>
#endif
#ifdef CONFIG_SCHED_SMT
some_global_thing = <expr>
#endif
}
...
#ifdef CONFIG_SCHED_SMT
some_other_global_thing = <expr>
#endif
#ifdef CONFIG_SCHED_MC
some_other_global_thing = <expr>
#endif
Which, looking a bit closer, was wrong (yes?)
It is a bit irregular that in one place we do the SMT processing first and
in another we do the MC processing first, but I guess it'll work OK.
We do need to be super-careful in the reviewing and testing here. If we
slip up we won't have a nice crash to tell us. Instead we'll find that
some machines with some configs will, under some workloads, take a few
percent longer than they should. We could waste people's time for years
until some developer stumbles across something.
next prev parent reply other threads:[~2006-02-01 2:22 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-26 9:51 [Patch] sched: new sched domain for representing multi-core Siddha, Suresh B
2006-01-27 0:08 ` Ingo Molnar
2006-01-27 3:51 ` Siddha, Suresh B
2006-01-28 0:00 ` Andrew Morton
2006-01-31 1:28 ` Siddha, Suresh B
2006-02-01 1:12 ` Andrew Morton
2006-02-01 1:48 ` Siddha, Suresh B
2006-02-01 2:21 ` Andrew Morton [this message]
2006-02-01 2:52 ` Siddha, Suresh B
2006-01-27 4:42 ` Andi Kleen
2006-01-28 1:45 ` Siddha, Suresh B
2006-01-29 16:56 ` Pavel Machek
2006-01-31 1:31 ` Siddha, Suresh B
2006-02-09 9:59 Samuel Thibault
2006-02-11 0:51 ` Siddha, Suresh B
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