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Re: [RFC] gcc feature request: Moving blocks into sections
- From: OndÅej BÃlka <neleai at seznam dot cz>
- To: Steven Rostedt <rostedt at goodmis dot org>
- Cc: Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>, Linus Torvalds <torvalds at linux-foundation dot org>, LKML <linux-kernel at vger dot kernel dot org>, gcc <gcc at gcc dot gnu dot org>, Ingo Molnar <mingo at kernel dot org>, "H. Peter Anvin" <hpa at linux dot intel dot com>, Thomas Gleixner <tglx at linutronix dot de>, David Daney <ddaney dot cavm at gmail dot com>, Behan Webster <behanw at converseincode dot com>, Peter Zijlstra <peterz at infradead dot org>, Herbert Xu <herbert at gondor dot apana dot org dot au>
- Date: Wed, 7 Aug 2013 07:06:01 +0200
- Subject: Re: [RFC] gcc feature request: Moving blocks into sections
- References: <CA+55aFwRHpL-3YObZfw6NxxDxMqQbiwp0=NnpotGj2RHDNF3iw at mail dot gmail dot com> <1375727977 dot 22073 dot 112 dot camel at gandalf dot local dot home> <CA+55aFyfvifCu=jDBH8LPmEHtvooVyo25dvJ+T6SQLhVidBBdQ at mail dot gmail dot com> <1375798783 dot 25420 dot 30 dot camel at gandalf dot local dot home> <CA+55aFwKYSwytooG50fyryWpVdGEk_v=vdB=L-kAyLmmSW=bkQ at mail dot gmail dot com> <1375811885 dot 25420 dot 44 dot camel at gandalf dot local dot home> <20130806203319 dot GA16170 at Krystal> <1375821817 dot 25420 dot 50 dot camel at gandalf dot local dot home> <1375836304 dot 25420 dot 76 dot camel at gandalf dot local dot home> <1375836960 dot 25420 dot 80 dot camel at gandalf dot local dot home>
On Tue, Aug 06, 2013 at 08:56:00PM -0400, Steven Rostedt wrote:
> On Tue, 2013-08-06 at 20:45 -0400, Steven Rostedt wrote:
>
> > [ 3.387362] short jumps: 106
> > [ 3.390277] long jumps: 330
> >
> > Thus, approximately 25%. Not bad.
>
> Also, where these happen to be is probably even more important than how
> many. If all the short jumps happen in slow paths, it's rather
> pointless. But they seem to be in some rather hot paths. I had it print
> out where it placed the short jumps too:
>
> The kmem_cache_* and the try_to_wake_up* are the hot paths that caught
> my eye.
>
> But still, is this worth it?
>
Add short_counter,long_counter and before increment counter before each
jump. That way we will know how many short/long jumps were taken.
> -- Steve
>