linux-kernel - Re: [tip:sched/core] sched: Rework sched

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Date:	Fri, 16 May 2014 10:57:37 +0100
From:	James Hogan <james.hogan@...tec.com>
To:	mingo@...nel.org, hanjun.guo@...aro.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>, schwidefsky@...ibm.com,
	Chris Metcalf <cmetcalf@...era.com>,
	Christoph Lameter <cl@...ux.com>, jason.low2@...com,
	tony.luck@...el.com,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	heiko.carstens@...ibm.com, Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, dietmar.eggemann@....com,
	"David S. Miller" <davem@...emloft.net>, bhelgaas@...gle.com,
	benh@...nel.crashing.org, preeti@...ux.vnet.ibm.com,
	fenghua.yu@...el.com, vincent.guittot@...aro.org
Cc:	linux-tip-commits@...r.kernel.org,
	James Hogan <james.hogan@...tec.com>,
	metag <linux-metag@...r.kernel.org>
Subject: Re: [tip:sched/core] sched: Rework sched_domain topology definition

Hi Vincent,

On 8 May 2014 11:43, tip-bot for Vincent Guittot <tipbot@...or.com> wrote:
> Commit-ID:  143e1e28cb40bed836b0a06567208bd7347c9672
> Gitweb:     http://git.kernel.org/tip/143e1e28cb40bed836b0a06567208bd7347c9672
> Author:     Vincent Guittot <vincent.guittot@...aro.org>
> AuthorDate: Fri, 11 Apr 2014 11:44:37 +0200
> Committer:  Ingo Molnar <mingo@...nel.org>
> CommitDate: Wed, 7 May 2014 13:33:49 +0200
>
> sched: Rework sched_domain topology definition
>
> We replace the old way to configure the scheduler topology with a new method
> which enables a platform to declare additionnal level (if needed).
>
> We still have a default topology table definition that can be used by platform
> that don't want more level than the SMT, MC, CPU and NUMA ones. This table can
> be overwritten by an arch which either wants to add new level where a load
> balance make sense like BOOK or powergating level or wants to change the flags
> configuration of some levels.
>
> For each level, we need a function pointer that returns cpumask for each cpu,
> a function pointer that returns the flags for the level and a name. Only flags
> that describe topology, can be set by an architecture. The current topology
> flags are:
>
>  SD_SHARE_CPUPOWER
>  SD_SHARE_PKG_RESOURCES
>  SD_NUMA
>  SD_ASYM_PACKING
>
> Then, each level must be a subset on the next one. The build sequence of the
> sched_domain will take care of removing useless levels like those with 1 CPU
> and those with the same CPU span and no more relevant information for
> load balancing than its children.
>
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> Tested-by: Dietmar Eggemann <dietmar.eggemann@....com>
> Reviewed-by: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>
> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Chris Metcalf <cmetcalf@...era.com>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: David S. Miller <davem@...emloft.net>
> Cc: Fenghua Yu <fenghua.yu@...el.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Hanjun Guo <hanjun.guo@...aro.org>
> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Cc: Jason Low <jason.low2@...com>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
> Cc: Tony Luck <tony.luck@...el.com>
> Cc: linux390@...ibm.com
> Cc: linux-ia64@...r.kernel.org
> Cc: linux-s390@...r.kernel.org
> Link: http://lkml.kernel.org/r/1397209481-28542-2-git-send-email-vincent.guittot@linaro.org
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> ---
>  arch/ia64/include/asm/topology.h |  24 ----
>  arch/s390/include/asm/topology.h |   2 -
>  arch/tile/include/asm/topology.h |  33 ------
>  include/linux/sched.h            |  53 +++++++++
>  include/linux/topology.h         | 128 +++------------------
>  kernel/sched/core.c              | 233 ++++++++++++++++++++-------------------
>  6 files changed, 186 insertions(+), 287 deletions(-)


> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 2a4298f..656b035 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -985,6 +1006,38 @@ void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms);
>
>  bool cpus_share_cache(int this_cpu, int that_cpu);
>
> +typedef const struct cpumask *(*sched_domain_mask_f)(int cpu);
> +typedef const int (*sched_domain_flags_f)(void);

I just noticed, since May 9th, linux-next (ARCH=metag, gcc 4.2.4, with
meta2_smp_defconfig) is showing loads of warnings due to the above
line:

include/linux/sched.h +1010 : warning: type qualifiers ignored on
function return type

Looks to me that the const serves no purpose in this context and could
be removed.

Cheers
James
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