linux-kernel - Re: [PATCH 1/2] i386: mce cleanup part1: functional change

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Date:	Wed, 10 Oct 2007 03:58:08 +0200
From:	Oleg Verych <olecom@...wer.upol.cz>
To:	Valdis.Kletnieks@...edu
Cc:	Joerg Roedel <joerg.roedel@....com>,
	Andi Kleen <andi@...stfloor.org>,
	Christoph Egger <Christoph.Egger@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] i386: mce cleanup part1: functional change

On Tue, Oct 09, 2007 at 04:46:46PM -0400, Valdis.Kletnieks@...edu wrote:
> On Tue, 09 Oct 2007 18:32:30 +0200, Oleg Verych said:
> > On Tue, Oct 09, 2007 at 06:06:05PM +0200, Joerg Roedel wrote:
> > > > cpu_has() returns int,
> > > > but would it be better to have something like
> > > > 
> > > >   	if (!mce_disabled &&
> > > > 	    !(c->x86_capability & (X86_FEATURE_MCA | X86_FEATURE_MCE)) {
> > > > 		printk(KERN_INFO "CPU%i: No machine check support available\n",
> > > > 			smp_processor_id());
> > > 
> > > This looks complicated and is harder to read. Its exactly the purpose of the
> > > cpu_has() macro to avoid such constructs.
> > 
> > It is done via test_bit(), which is designed for IO access with all that
> > `const volatile' stuff, 2 x unnecessary, can't be optimized here (IMHO).
> 
> If this code is getting called often enough that optimization matters, you
> got *bigger* issues to worry about than optimization.  Looks like it should
> only happen once at boot time.

Text size matters even on static storages. A Linuxbios image not fitting
to the 2M flash, etc.

Thanks.
____
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