linux-kernel - Re: [PATCH] bitmap_equal memcmp optimization for s390

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Message-Id: <20160609164532.23f05026@mschwide>
Date:	Thu, 9 Jun 2016 16:45:32 +0200
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	David Howells <dhowells@...hat.com>
Cc:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] bitmap_equal memcmp optimization for s390

On Thu, 09 Jun 2016 15:26:47 +0100
David Howells <dhowells@...hat.com> wrote:

> Martin Schwidefsky <schwidefsky@...ibm.com> wrote:
> 
> > I hesitate to put another CONFIG_S390 into common code, alternatively
> > __HAVE_ARCH_MEMCMP could be used. There are 7 architectures with the
> > define: arc, arm64, blackfin, frv, powerpc, s390 and sparc.
> > Of those I guess only powerpc, s390 and sparc will have configs with
> > (NR_CPUS > BITS_PER_LONG). For (NR_CPUS <= BITS_PER_LONG) the xor
> > optimization is used.
> 
> FRV doesn't have __HAVE_ARCH_MEMCMP for __KERNEL__.

Yes indeed. How strange to define __HAVE_ARCH_xxx for user space only.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.