linux-kernel - Re: [RFC] NUMA futex hashing

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Date:	08 Aug 2006 06:07:47 -0400
From:	Jes Sorensen <jes@....com>
To:	Andi Kleen <ak@...e.de>
Cc:	linux-kernel@...r.kernel.org,
	"Shai Fultheim (Shai@...lex86.org)" <shai@...lex86.org>,
	pravin b shelar <pravin.shelar@...softinc.com>
Subject: Re: [RFC] NUMA futex hashing

>>>>> "Andi" == Andi Kleen <ak@...e.de> writes:

Andi> Jes Sorensen <jes@....com> writes:
>>  Using that argument, all you need to do is to add the alignment
>> ____cacheline_aligned_in_smp to the definition of struct
>> futex_hash_bucket and the problem is solved, given that the
>> internode cacheline in a NUMA system is defined to be the same as
>> the SMP cacheline size.

Andi> Yes but it would waste quite a lot of memory and cache.  Wasted
Andi> cache = slow.

Compared to the extra level of indirection, I doubt it would be
measurable. The cache space is barely wasted, we're talking
approximately half a cacheline per futex hash bucket in use.

Jes
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