From: Alan Modra <amodra@gmail.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@ozlabs.org, Anton Blanchard <anton@samba.org>
Subject: Re: [PATCH] powerpc: Optimise per cpu accesses on 64bit
Date: Wed, 2 Jun 2010 08:10:26 +0930 [thread overview]
Message-ID: <20100601224026.GG5631@bubble.grove.modra.org> (raw)
In-Reply-To: <1275375920.1931.699.camel@pasglop>
On Tue, Jun 01, 2010 at 05:05:20PM +1000, Benjamin Herrenschmidt wrote:
> On Tue, 2010-06-01 at 14:45 +1000, Anton Blanchard wrote:
> > Now we dynamically allocate the paca array, it takes an extra load
> > whenever we want to access another cpu's paca. One place we do that a lot
> > is per cpu variables. A simple example:
>
> Can't we dedicate a GPR instead ? Or it isn't worth it ? Something we
> almost never use in the kernel like r12 ?
Not r12. It is used in function prologue and epilogue code. If you
want a dedicated gpr I think you'll need to use (and lose) one of the
non-volatile regs.
--
Alan Modra
Australia Development Lab, IBM
next prev parent reply other threads:[~2010-06-01 22:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-01 4:45 [PATCH] powerpc: Optimise per cpu accesses on 64bit Anton Blanchard
2010-06-01 7:05 ` Benjamin Herrenschmidt
2010-06-01 22:40 ` Alan Modra [this message]
2010-06-01 23:50 ` Benjamin Herrenschmidt
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