linux-kernel - Re: [rfc] x86: optimise page fault path a little

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Date:	Thu, 13 Nov 2008 17:06:33 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [rfc] x86: optimise page fault path a little


* Nick Piggin <npiggin@...e.de> wrote:

> > 32-bit should use oops_begin() too. Solves the previous comment as 
> > well.
> > 
> > > +#ifdef CONFIG_X86_32
> > > +	die("Oops", regs, error_code);
> > > +	bust_spinlocks(0);
> > > +	do_exit(SIGKILL);
> > > +#else
> > > +	if (__die("Oops", regs, error_code))
> > > +		regs = NULL;
> > > +	/* Executive summary in case the body of the oops scrolled away */
> > > +	printk(KERN_EMERG "CR2: %016lx\n", address);
> > > +	oops_end(flags, regs, SIGKILL);
> > > +#endif
> > 
> > this difference seems unnecessary too - 32-bit should use oops_end() 
> > too.
> 
> Probably all 3 good comments, but I didn't want to be tempted into 
> changing behaviour (modulo adding bugs). Easy to merge them up in a 
> subsequent patch, however...

please do feel tempted to clean this code up - and if it changes 
behavior, split it up into smaller steps. The patch is already quite 
large with a flux of 430 lines:

 1 file changed, 251 insertions(+), 188 deletions(-)

... your primary goal is faster code, we also want cleaner code. I 
think we can meet in the middle, have faster _and_ cleaner code, and 
it's a done deal ;)

	Ingo
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