linux-kernel - Re: [PATCH 1/2] futex: eliminate cache miss from futex

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Message-ID: <20150622135505.GU3644@twins.programming.kicks-ass.net>
Date:	Mon, 22 Jun 2015 15:55:05 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Richard Weinberger <richard@....at>,
	Andy Lutomirski <luto@...capital.net>,
	Darren Hart <darren@...art.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] futex: eliminate cache miss from futex_hash()

On Mon, Jun 22, 2015 at 03:45:10PM +0200, Rasmus Villemoes wrote:
> On Mon, Jun 22 2015, Peter Zijlstra <peterz@...radead.org> wrote:

> > Does: __aligned(sizeof(__futex_data)), work?

> Unfortunately not:

> > Because 16 might waste 8 bytes on 32bit.
> 
> Yeah, wasting >= 48 bytes was the reason I didn't make it
> ____cacheline_aligned. If 8 bytes is also too much, I suppose one could
> just give the struct a tag and then use sizeof(struct futex_data).

Nah, its probably fine, just wondering if it could be done better.
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