linux-kernel - Re: [PATCH] sched: Enable arch-specific asym packing option in sched domain

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Message-ID: <5568.1336171672@neuling.org>
Date:	Sat, 05 May 2012 08:47:52 +1000
From:	Michael Neuling <mikey@...ling.org>
To:	Diwakar Tundlam <dtundlam@...dia.com>
cc:	'Peter Zijlstra' <a.p.zijlstra@...llo.nl>,
	'Ingo Molnar' <mingo@...nel.org>,
	'Andrew Morton' <akpm@...ux-foundation.org>,
	'Christoph Lameter' <cl@...two.org>,
	'Stephen Rothwell' <sfr@...b.auug.org.au>,
	'Benjamin Herrenschmidt' <benh@...nel.crashing.org>,
	'David Rientjes' <rientjes@...gle.com>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
	Peter De Schrijver <pdeschrijver@...dia.com>
Subject: Re: [PATCH] sched: Enable arch-specific asym packing option in sched domain

Diwakar Tundlam <dtundlam@...dia.com> wrote:

> >> A repost doesn't make it right to add sibling (SMT) properties to a package/socket and will still upset Power7.
> 
> Agreed. I only fixed the whitespace and commitId.
> 
> arch_sd_sibling_asym_packing() is already present under ifdef CONFIG_SMT.
> I didn't touch that. I only added it to SD_CPU_INIT for all cpu's.
> I assumed Power7 shouldn't use SD_CPU_INIT.

You are using sibling at the cpu level.  POWER7 sets this at the sibling
level and we don't really want it at the cpu level.

> I don't understand Power7 arch to comment on impact.
> Michael Neuling should review this carefully and advise.

Ask Peter said, it's broken for POWER7.  We don't want to set this at
the cpu level.

> Maybe I should define a separate weak symbol, say
> arch_sd_bias_to_lower_num_cpu()?  Then Power7 can define
> arch_sd_sibling_asym_packing() to be '1' and it will not break all-cpu
> init.

This sounds better but I'd follow the old name call it
arch_sd_cpu_asym_packing()

Mikey
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