From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Kevin Hao <haokexin@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>, Torsten Duwe <duwe@lst.de>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [RFC] powerpc: use ticket spin lock for !CONFIG_PPC_SPLPAR
Date: Fri, 13 Mar 2015 18:07:18 +1100 [thread overview]
Message-ID: <1426230438.17565.162.camel@kernel.crashing.org> (raw)
In-Reply-To: <20150313060913.GC24485@pek-khao-d1.corp.ad.wrs.com>
On Fri, 2015-03-13 at 14:09 +0800, Kevin Hao wrote:
> On Thu, Mar 12, 2015 at 04:24:10PM +0100, Torsten Duwe wrote:
> > But generally, which platforms would benefit most from this change?
>
> In theory, the more cpus the platform has, the more serious the thundering
> herd problem is. So the latest platforms which has more cpus would benefit
> most.
In fact, pseries would be one to benefit ... it would be nice to find a
way to sort out the lock owner problem.
One idea I had was to keep the owners elsewhere, some kind of hash chain
of "taken locks" hashed on the lock address. There shouldn't be *that*
many locks held at a given point in time.
Trying to keep the owner in a separate & non-atomic part of the lock
proved being too hard due to how the lockref and generic code are
interwined, though maybe somebody smarter can find a trick :-)
Cheers,
Ben.
next prev parent reply other threads:[~2015-03-13 7:07 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-12 10:55 [RFC] powerpc: use ticket spin lock for !CONFIG_PPC_SPLPAR Kevin Hao
2015-03-12 11:13 ` Benjamin Herrenschmidt
2015-03-12 15:24 ` Torsten Duwe
2015-03-13 6:09 ` Kevin Hao
2015-03-13 7:07 ` Benjamin Herrenschmidt [this message]
2015-03-13 5:59 ` Kevin Hao
2015-03-13 7:09 ` Michael Ellerman
2015-03-13 7:14 ` Benjamin Herrenschmidt
2015-03-16 0:25 ` Sam Bobroff
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