Date: Wed, 7 Aug 2013 19:40:15 +0000
From: Christoph Lameter <cl@gentwo.org>
To: Kent Overstreet <kmo@daterainc.com>
cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
        Tejun Heo <tj@kernel.org>, Oleg Nesterov <oleg@redhat.com>,
        Ingo Molnar <mingo@redhat.com>, Andi Kleen <andi@firstfloor.org>,
        Jens Axboe <axboe@kernel.dk>,
        "Nicholas A. Bellinger" <nab@linux-iscsi.org>
Subject: Re: [PATCH 04/10] idr: Percpu ida
In-Reply-To: <20130807183345.GA11612@kmo-pixel>
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On Wed, 7 Aug 2013, Kent Overstreet wrote:

> I was breaking it apart because I was using this_cpu elsewhere too - for
> the bitmap of which cpus have non empty freelists.

this_cpu can be retrieved with smp_processor_id().

> Or is this_cpu_ptr() doing something smarter than per_cpu_ptr(ptr,
> smp_processer_id())? There's so many variants I'm not 100% sure they're
> the same.

Yes it is. It uses a sepecial register that contains the offset of this
cpus per cpu area instead of going through the table of all processor
offsets. Its less code.

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