From: Ingo Molnar <mingo@kernel.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Al Viro <viro@zeniv.linux.org.uk>,
the arch/x86 maintainers <x86@kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] speeding up the stat() family of system calls...
Date: Sun, 12 Jan 2014 18:46:07 +0100 [thread overview]
Message-ID: <20140112174607.GA26698@gmail.com> (raw)
In-Reply-To: <52BE0D89.3080405@zytor.com>
* H. Peter Anvin <hpa@zytor.com> wrote:
> 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.
Yeah, defconfig builds are better for size comparisons, at least on
x86 they are distro-config derived so a lot more relevant to real life
than allyesconfig or allmodconfig.
Thanks,
Ingo
prev parent reply other threads:[~2014-01-12 17:46 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-21 20:27 [RFC] speeding up the stat() family of system calls Linus Torvalds
2013-12-21 22:54 ` John Stoffel
2013-12-22 0:11 ` Linus Torvalds
2013-12-24 0:00 ` H. Peter Anvin
2013-12-24 0:12 ` Linus Torvalds
2013-12-24 6:00 ` H. Peter Anvin
2013-12-24 20:46 ` Ingo Molnar
2013-12-26 19:00 ` Linus Torvalds
2013-12-27 0:45 ` H. Peter Anvin
2013-12-27 3:18 ` H. Peter Anvin
2013-12-27 6:09 ` H. Peter Anvin
2013-12-27 23:30 ` H. Peter Anvin
2014-01-12 17:46 ` Ingo Molnar [this message]
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