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From: Nicholas Piggin <npiggin@gmail.com>
To: Anton Blanchard <anton@samba.org>
Cc: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au,
	agraf@suse.de, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc: Align hot loops of memset() and backwards_memcpy()
Date: Wed, 28 Sep 2016 05:03:16 +1000	[thread overview]
Message-ID: <20160928050316.0290e4c5@roar.ozlabs.ibm.com> (raw)
In-Reply-To: <20160925213659.18971b96@kryten>

On Sun, 25 Sep 2016 21:36:59 +1000
Anton Blanchard <anton@samba.org> wrote:

> Hi Nick,
> 
> > Hmm. If we execute this loop once, we'll only fetch additional nops.
> > Twice, and we make up for them by not fetching unused instructions.
> > More than twice and we may start winning.
> > 
> > For large sizes it probably helps, but I'd like to see what sizes
> > memset sees.  
> 
> I noticed this in an nginx web serving test. There are some 1 and 2
> iteration calls, but quite a few larger ones - get_empty_filp() goes for
> 4 iterations and sk_prot_alloc() for 26 iterations.

Hi Anton,

I didn't have anything against the patch as such, I just wondered if
it's likely to be an overall win.

Thanks,
Nick

  reply	other threads:[~2016-09-27 19:03 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-04  6:53 [PATCH] powerpc: Align hot loops of memset() and backwards_memcpy() Anton Blanchard
2016-08-04  7:49 ` Christophe Leroy
2016-08-04 10:36   ` Anton Blanchard
2016-08-05 11:00 ` Nicholas Piggin
2016-08-05 11:54   ` Anton Blanchard
2016-09-25 11:36   ` Anton Blanchard
2016-09-27 19:03     ` Nicholas Piggin [this message]
2016-10-05  2:36 ` Michael Ellerman

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