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From: Joe Perches <joe@perches.com>
To: Andi Kleen <andi@firstfloor.org>, Alexey Dobriyan <adobriyan@gmail.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	viro@zeniv.linux.org.uk
Subject: Re: [PATCH] proc: faster /proc/*/status
Date: Sun, 07 Aug 2016 10:39:25 -0700	[thread overview]
Message-ID: <1470591565.28648.40.camel@perches.com> (raw)
In-Reply-To: <20160807165947.GX5871@two.firstfloor.org>

On Sun, 2016-08-07 at 09:59 -0700, Andi Kleen wrote:
> > And then what? Parsing format string is still be there.
> Perhaps could have a fast path for simple cases.
> > 
> > This is first line of profile of the first function (format_decode)
> > 
> >        │     static noinline_for_stack
> >        │     int format_decode(const char *fmt, struct printf_spec *spec)
> >        │     {
> >  10.38 │       push   %rbp			<===
> >   1.07 │       mov    %rsp,%rbp
> >   1.09 │       push   %r12
> >   4.51 │       mov    %rsi,%r12
> >   1.40 │       push   %rbx
> >   1.86 │       mov    %rdi,%rbx
> >        │       sub    $0x8,%rsp
> > 
> > It is so bloated that gcc needs to be asked to not screw up with stack
> > size.
> What happens when you drop all the noinlines for this? I assume
> this would alread make it faster. And now that we have bigger
> stacks we can likely tolerate it.

%pV recurses through these code paths.
I believe the maximum current recursion depth is 3.

  reply	other threads:[~2016-08-07 17:39 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-06 12:56 Alexey Dobriyan
2016-08-06 22:41 ` Joe Perches
2016-08-09  3:02   ` [PATCH] seq/proc: Modify seq_put_decimal_[u]ll to take a const char *, not char Joe Perches
2016-08-07  3:16 ` [PATCH] proc: faster /proc/*/status Andi Kleen
2016-08-07  8:53   ` Alexey Dobriyan
2016-08-07 16:59     ` Andi Kleen
2016-08-07 17:39       ` Joe Perches [this message]
2016-08-07 17:44         ` Andi Kleen
2016-08-07 21:22           ` Joe Perches
2016-08-09 23:25             ` Andrew Morton
2016-08-10  6:38               ` [RFC PATCH] meminfo: Break apart a very long seq_printf with #ifdefs Joe Perches
2016-08-11 21:50                 ` Andrew Morton
2016-08-11 21:57                   ` Joe Perches

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