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From: Will Deacon <will.deacon@arm.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH 2/2] word-at-a-time: provide generic big-endian zero_bytemask implementation
Date: Thu, 12 Dec 2013 17:02:34 +0000	[thread overview]
Message-ID: <20131212170234.GJ12617@mudshark.cambridge.arm.com> (raw)
In-Reply-To: <CA+55aFzVrAQnmt7a_SKqOVyHrY55_uRP1yL4NGAXspeee6ZkRQ@mail.gmail.com>

Hi Linus,

On Tue, Dec 10, 2013 at 08:08:20PM +0000, Linus Torvalds wrote:
> Hmm. Did you try to time this?

I took it for a spin on a big-endian ARMv7 platform (32-bit) and the hashing is
around 40% faster.

> Also, I really have #ifdef's in code, and I think we'd be better off
> just exposing a function that does this
> 
> +#ifdef __BIG_ENDIAN
> +       mask = ~(~0ul >> tcount*8);
> +#else
>         mask = ~(~0ul << tcount*8);
> +#endif
> 
> thing. I think it would logically go together with zero_bytemask(),
> call it something like "bytemask_from_count()" or something. Hmm? It's
> basically just the reverse of "count_masked_bytes()", which we also
> have an abstraction for.

Yup, that's a good idea, I can probably just add something to dcache.h.
I'll spin a v2.

Cheers,

Will

  reply	other threads:[~2013-12-12 17:02 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-12-10 19:10 [PATCH 1/2] dcache: allow word-at-a-time name hashing with big-endian CPUs Will Deacon
2013-12-10 19:10 ` [PATCH 2/2] word-at-a-time: provide generic big-endian zero_bytemask implementation Will Deacon
2013-12-10 20:08   ` Linus Torvalds
2013-12-12 17:02     ` Will Deacon [this message]
2013-12-12 18:46 ` [PATCH 1/2] dcache: allow word-at-a-time name hashing with big-endian CPUs Christoph Hellwig

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