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Date: Fri, 27 Dec 2013 15:30:17 -0800 From: "H. Peter Anvin" <hpa@...or.com> To: Linus Torvalds <torvalds@...ux-foundation.org>, Ingo Molnar <mingo@...nel.org> CC: Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, Al Viro <viro@...iv.linux.org.uk>, the arch/x86 maintainers <x86@...nel.org>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [RFC] speeding up the stat() family of system calls... On 12/26/2013 10:09 PM, H. Peter Anvin wrote: > On 12/26/2013 11:00 AM, Linus Torvalds wrote: >> >> Interestingly, looking at the cp_new_stat() profiles, the games we >> play to get efficient range checking seem to actually hurt us. Maybe >> it's the "sbb" that is just expensive, or maybe it's turning a (very >> predictable) conditional branch into a data dependency chain instead. >> Or maybe it's just random noise in my profiles that happened to make >> those sbb's look bad. >> > > Much to my surprise, this patch adds almost 10K of text to an > "allyesconfig" build. I wouldn't have expected it. I'll look at it > some more tomorrow. > Mystery solved... it is all code added by gcov &c because a new (inline) function is added to the code base. So it is fluff, not real. -hpa -- 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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