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Date: Fri, 5 Aug 2016 21:54:37 +1000
From: Anton Blanchard <anton@samba.org>
To: Nicholas Piggin <npiggin@gmail.com>
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()
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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 found this in a trace of nginx web serving. Looking back at it,
get_empty_filp() zeros a struct file, and we go through the loop 4
times. We might want to look more generally at what lengths memset() is
called with though.

Anton