From: catalin.marinas@arm•com (Catalin Marinas)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC PATCH v3 3/6] sched: pack small tasks
Date: Wed, 27 Mar 2013 18:01:52 +0000 [thread overview]
Message-ID: <20130327180152.GB17642@arm.com> (raw)
In-Reply-To: <CAKfTPtAKTh76-4tVe=ZcEc_hh0J1CaKeU_n3KD3D3Po4T2FMbQ@mail.gmail.com>
On Wed, Mar 27, 2013 at 05:20:28PM +0000, Vincent Guittot wrote:
> On 27 March 2013 17:36, Catalin Marinas <catalin.marinas@arm•com> wrote:
> > On Wed, Mar 27, 2013 at 02:13:54PM +0000, Peter Zijlstra wrote:
> >> On Wed, 2013-03-27 at 11:18 +0000, Catalin Marinas wrote:
> >> > On Wed, Mar 27, 2013 at 09:00:20AM +0000, Peter Zijlstra wrote:
> >> > > On Wed, 2013-03-27 at 09:54 +0100, Vincent Guittot wrote:
> >> > > > It's not mandatory to have little cores on low numbers even if it's
> >> > > > advised
> >> > >
> >> > > ARGH!
> >> >
> >> > I haven't followed this thread closely, so just a random comment from
> >> > me. An argument from some is that they want to boot Linux on the big CPU
> >> > to be quicker. The most convenient is to have the big CPU at 0.
> >>
> >> I suppose that's almost sensible ;-) I just despair at the amount of
> >> variation that's allowed.
> >>
> >> I'm guessing that swapping cpus in the bootloader or someplace really
> >> early is equally hard in that we (Linux) assume we boot on cpu 0 or
> >> something like that?
> >
> > I think it's worth trying (by changing the CPU topology in the DT). At a
> > quick look, I don't see anything hard-coded in the kernel boot sequence.
> > It uses smp_processor_id() which translates to
> > current_thread_info()->cpu on ARM. I'm not sure how early we need this
> > but it's probably after DT parsing, so we could set 'cpu' to a non-zero
> > value for the booting processor. There are a few tweaks in the arch/arm
> > code code with cpu_logical_map setup (which maps between
> > smp_processor_id and the actual hardware CPU id and assumes 0 is the
> > booting CPU).
>
> The are few other places in the code that makes the assumption that
> the 1st online CPU is the booting CPU like the disable_nonboot_cpus
Another thing - boot_cpu_init() is using smp_processor_id() before we
get the setup_arch() call where we parse the DT.
--
Catalin
next prev parent reply other threads:[~2013-03-27 18:01 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-22 12:25 [RFC PATCH v3 0/6] sched: packing small tasks Vincent Guittot
2013-03-22 12:25 ` [RFC PATCH v3 1/6] Revert "sched: Introduce temporary FAIR_GROUP_SCHED dependency for load-tracking" Vincent Guittot
2013-03-22 12:25 ` [RFC PATCH v3 2/6] sched: add a new SD_SHARE_POWERDOMAIN flag for sched_domain Vincent Guittot
2013-03-22 12:25 ` [RFC PATCH v3 3/6] sched: pack small tasks Vincent Guittot
2013-03-26 12:26 ` Peter Zijlstra
2013-03-27 10:21 ` Preeti U Murthy
2013-03-27 11:00 ` Vincent Guittot
2013-04-26 10:30 ` Peter Zijlstra
2013-04-26 11:34 ` Vincent Guittot
2013-04-26 10:18 ` Peter Zijlstra
2013-04-26 10:32 ` Preeti U Murthy
2013-03-26 12:37 ` Peter Zijlstra
2013-03-26 13:00 ` Vincent Guittot
2013-03-27 4:33 ` Preeti U Murthy
2013-03-27 4:48 ` Alex Shi
2013-03-27 8:51 ` Peter Zijlstra
2013-03-26 12:46 ` Peter Zijlstra
2013-03-26 13:53 ` Vincent Guittot
2013-03-26 15:29 ` Arjan van de Ven
2013-03-27 8:46 ` Peter Zijlstra
2013-03-27 8:54 ` Vincent Guittot
2013-03-27 9:00 ` Peter Zijlstra
2013-03-27 11:18 ` Catalin Marinas
2013-03-27 14:13 ` Peter Zijlstra
2013-03-27 16:36 ` Catalin Marinas
2013-03-27 17:18 ` Nicolas Pitre
2013-03-27 17:37 ` Catalin Marinas
2013-03-27 17:20 ` Vincent Guittot
2013-03-27 18:01 ` Catalin Marinas [this message]
2013-03-27 15:37 ` Nicolas Pitre
2013-03-22 12:25 ` [RFC PATCH v3 4/6] sched: secure access to other CPU statistics Vincent Guittot
2013-03-26 12:50 ` Peter Zijlstra
2013-03-26 13:06 ` Vincent Guittot
2013-03-22 12:25 ` [RFC PATCH v3 5/6] sched: pack the idle load balance Vincent Guittot
2013-03-26 12:52 ` Peter Zijlstra
2013-03-26 14:03 ` Vincent Guittot
2013-03-26 14:42 ` Peter Zijlstra
2013-03-26 15:55 ` Vincent Guittot
2013-03-27 4:56 ` Alex Shi
2013-03-27 8:05 ` Vincent Guittot
2013-03-27 8:47 ` Alex Shi
2013-03-27 10:30 ` Vincent Guittot
2013-03-27 13:32 ` Alex Shi
2013-03-27 8:49 ` Peter Zijlstra
2013-04-05 11:08 ` Vincent Guittot
2013-04-22 5:45 ` Preeti U Murthy
[not found] ` <CAKfTPtCCCifC=c+xjjnAH_HSqkR80PiQoddQKXPHuZwZawbvcA@mail.gmail.com>
2013-04-23 2:23 ` Alex Shi
2013-04-23 4:57 ` Preeti U Murthy
2013-04-23 15:30 ` Arjan van de Ven
2013-04-26 10:54 ` Peter Zijlstra
2013-04-23 4:36 ` Preeti U Murthy
2013-03-22 12:25 ` [RFC PATCH v3 6/6] ARM: sched: clear SD_SHARE_POWERDOMAIN Vincent Guittot
2013-03-23 11:55 ` [RFC PATCH v3 0/6] sched: packing small tasks Preeti U Murthy
2013-03-25 9:58 ` Vincent Guittot
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