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Date: Thu, 10 Sep 2015 11:36:18 -0500 (CDT)
From: Christoph Lameter <cl@linux.com>
Subject: Re: Store Buffers (was Re: Is it OK to pass non-acquired objects to
 kfree?)
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To: Vlastimil Babka <vbabka@suse.cz>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Dmitry Vyukov <dvyukov@google.com>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Andrew Morton <akpm@linux-foundation.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, Andrey Konovalov <andreyknvl@google.com>, Alexander Potapenko <glider@google.com>

On Thu, 10 Sep 2015, Vlastimil Babka wrote:

> > For a partial cacheline it would have to read the rest of the cacheline
> > before updating. And I would expect the processor to have exclusive access
> > to the cacheline that is held in a store buffer. If not then there is
> > trouble afoot.
>
> IIRC that (or something similar with same guarantees) basically happens on x86
> when you use the LOCK prefix, i.e. for atomic inc etc. Doing that always would
> destroy performance.

Well yes but it also happens anytime you try to write to a cacheline.

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