linux-kernel - Re: [PATCH] mm: introduce numa_zero

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Message-ID: <CAAmzW4P-MT9u_VzJ59t163TFPuDcyNX=tb5sC6WZ8sO20_Zjcg@mail.gmail.com>
Date:	Mon, 17 Dec 2012 22:58:42 +0900
From:	JoonSoo Kim <js1304@...il.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Christoph Lameter <cl@...ux.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH] mm: introduce numa_zero_pfn

2012/12/13 Andi Kleen <andi@...stfloor.org>:
>> I would expect a processor to fetch the zero page cachelines from the l3
>> cache from other sockets avoiding memory transactions altogether. The zero
>> page is likely in use somewhere so no typically no memory accesses should
>> occur in a system.
>
> It depends on how effectively the workload uses the caches. If something
> is a cache pig of the L3 cache, then even shareable cache lines may need
> to be refetched regularly.
>
> But if your workloads spends a significant part of its time reading
> from zero page read only data there is something wrong with the workload.
>
> I would do some data profiling first to really prove that is the case.

Okay.
I didn't know about L3 cache, before.
Now, I think that I need some data profiling!
Thanks for comment.
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