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Date: Wed, 22 Apr 2009 14:19:00 -0700 (PDT) From: Linus Torvalds <torvalds@...ux-foundation.org> To: Andi Kleen <andi@...stfloor.org> cc: Ingo Molnar <mingo@...e.hu>, Jeff Garzik <jeff@...zik.org>, LKML <linux-kernel@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org Subject: Re: [PATCH] X86-32: Let gcc decide whether to inline memcpy was Re: New x86 warning On Wed, 22 Apr 2009, Andi Kleen wrote: > > AFAIK it's all true on 3.2+ when it can figure out the alignment > (but some gcc versions had problems passing the alignment around e.g. > through inlining), under the assumption that out of line can do > a better job with unaligned data. That's not true with my patch, > but could be true in theory. Maybe it was the unaligned case that I remember. Because it's definitely not true that out-of-line code can do any better with unaligned data, at least not for small constants. And the case I remember was for some silly 8-byte case or similar. > Quick test here: How about you just compile the kernel with gcc-3.2 and compare the number of calls to memcpy before-and-after instead? That's the real test. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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