linux-kernel - Re: [PATCH v3] powerpc32: memset: only use dcbz once cache is enabled

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Message-ID: <87bnd5xyiz.fsf@steelpick.2x.cz>
Date:	Mon, 14 Sep 2015 09:15:00 +0200
From:	Michal Sojka <sojkam1@....cvut.cz>
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
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v3] powerpc32: memset: only use dcbz once cache is enabled

On Mon, Sep 14 2015, Christophe Leroy wrote:
> memset() uses instruction dcbz to speed up clearing by not wasting time
> loading cache line with data that will be overwritten.
> Some platform like mpc52xx do no have cache active at startup and
> can therefore not use memset(). Allthough no part of the code
> explicitly uses memset(), GCC may makes calls to it.
>
> This patch modifies memset() such that at startup, memset()
> unconditionally jumps to simple_memset() which doesn't use
> the dcbz instruction.

I tested both v3 patches (memcpy and memset) and they work for me.

Thanks
-Michal
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