linux-kernel - RE: [PATCH v2 0/6] powerpc32: replace memcpy and memset by cacheable alternatives

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Date:	Tue, 19 May 2015 11:43:13 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Christophe Leroy' <christophe.leroy@....fr>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	"Michael Ellerman" <mpe@...erman.id.au>,
	"scottwood@...escale.com" <scottwood@...escale.com>
CC:	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 0/6] powerpc32: replace memcpy and memset by
 cacheable alternatives

From: Christophe Leroy
> Sent: 19 May 2015 11:08
>
> This patchset implements use of cacheable versions of memset and
> memcpy since when the destination is not cacheable, memset_io
> and memcpy_toio are used.

This isn't the right list to ask, but:

Can someone fix the x86 versions of memset/memcpy (and the _io variants)
so that they don't end up being 'rep movsb' on new intel cpus?

I've a C2558 Atom which has the optimised 'rep movsb' hardware.
Copies to/from uncached locations are now done 'byte by byte'.
As well as kernel code this affects userpace copying to/from
mmap()ed PCIe space.
64bit reads are slow enough, making it 8 times slower is horrid.

I suspect this affect some network drivers as well.

	David