Date: Tue, 24 Sep 2013 10:04:36 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>,
        Paul Mackerras <paulus@au1.ibm.com>, Ingo Molnar <mingo@kernel.org>,
        James Hogan <james.hogan@imgtec.com>,
        "James E.J. Bottomley" <jejb@parisc-linux.org>,
        Helge Deller <deller@gmx.de>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        "David S. Miller" <davem@davemloft.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Anton Blanchard <anton@au1.ibm.com>
Subject: Re: [RFC GIT PULL] softirq: Consolidation and stack overrun fix
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On Tue, Sep 24, 2013 at 11:52:07AM +1000, Benjamin Herrenschmidt wrote:
> So if that holds, we have a solid way to do per-cpu. On one side, I tend
> to think that r13 being task/thread/thread_info is probably a better
> overall choice, I'm worried that going in a different direction than x86
> means generic code will get "tuned" to use per-cpu for performance
> critical stuff rather than task/thread/thread_info in inflexible ways.

The plus side of per-cpu over per-task is that one typically has a lot
less cpus than tasks. Also, its far easier/cheaper to iterate cpus than
it is to iterate tasks.
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