linux-kernel - Re: [PATCH v4 12/15] perf report: cache failed lookups of inlined frames

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Date:   Sun, 08 Oct 2017 22:28:26 +0200
From:   Milian Wolff <milian.wolff@...b.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     acme@...nel.org, jolsa@...nel.org,
        Jin Yao <yao.jin@...ux.intel.com>,
        Linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>, kernel-team@....com
Subject: Re: [PATCH v4 12/15] perf report: cache failed lookups of inlined frames

On Donnerstag, 5. Oktober 2017 05:43:38 CEST Namhyung Kim wrote:
> On Sun, Oct 01, 2017 at 04:30:57PM +0200, Milian Wolff wrote:
> > When no inlined frames could be found for a given address,
> > we did not store this information anywhere. That means we
> > potentially do the costly inliner lookup repeatedly for
> > cases where we know it can never succeed.
> > 
> > This patch makes dso__parse_addr_inlines always return a
> > valid inline_node. It will be empty when no inliners are
> > found. This enables us to cache the empty list in the DSO,
> > thereby improving the performance when many addresses
> > fail to find the inliners.
> > 
> > For my trivial example, the performance impact is already
> > quite significant:
> > 
> > Before:
> > 
> > ~~~~~
> > 
> >  Performance counter stats for 'perf report --stdio --inline -g srcline -s 
srcline' (5 runs):
> >         594.804032      task-clock (msec)         #    0.998 CPUs utilized
> >                    ( +-  0.07% )>         
> >                 53      context-switches          #    0.089 K/sec        
> >                            ( +-  4.09% )>                 
> >                  0      cpu-migrations            #    0.000 K/sec        
> >                             ( +-100.00% )>              
> >              5,687      page-faults               #    0.010 M/sec        
> >                         ( +-  0.02% )>      
> >      2,300,918,213      cycles                    #    3.868 GHz          
> >                 ( +-  0.09% ) 4,395,839,080      instructions            
> >       #    1.91  insn per cycle           ( +-  0.00% )>      
> >        939,177,205      branches                  # 1578.969 M/sec        
> >                   ( +-  0.00% )>        
> >         11,824,633      branch-misses             #    1.26% of all
> >         branches          ( +-  0.10% )>        
> >        0.596246531 seconds time elapsed                                   
> >              ( +-  0.07% )> 
> > ~~~~~
> > 
> > After:
> > 
> > ~~~~~
> > 
> >  Performance counter stats for 'perf report --stdio --inline -g srcline -s 
srcline' (5 runs):
> >         113.111405      task-clock (msec)         #    0.990 CPUs utilized
> >                    ( +-  0.89% )>         
> >                 29      context-switches          #    0.255 K/sec        
> >                            ( +- 54.25% )>                 
> >                  0      cpu-migrations            #    0.000 K/sec
> >              
> >              5,380      page-faults               #    0.048 M/sec        
> >                         ( +-  0.01% )>        
> >        432,378,779      cycles                    #    3.823 GHz          
> >                   ( +-  0.75% ) 670,057,633      instructions            
> >         #    1.55  insn per cycle           ( +-  0.01% ) 141,001,247    
> >         branches                  # 1246.570 M/sec                    (
> >        +-  0.01% )>        
> >          2,346,845      branch-misses             #    1.66% of all
> >          branches          ( +-  0.19% )>        
> >        0.114222393 seconds time elapsed                                   
> >              ( +-  1.19% )> 
> > ~~~~~
> > 
> > Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> > Cc: David Ahern <dsahern@...il.com>
> > Cc: Namhyung Kim <namhyung@...nel.org>
> > Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > Cc: Yao Jin <yao.jin@...ux.intel.com>
> > Signed-off-by: Milian Wolff <milian.wolff@...b.com>
> > ---
> 
> [SNIP]
> 
> > diff --git a/tools/perf/util/srcline.c b/tools/perf/util/srcline.c
> > index 69241d805275..26d9954dc19e 100644
> > --- a/tools/perf/util/srcline.c
> > +++ b/tools/perf/util/srcline.c
> > @@ -353,17 +353,8 @@ static struct inline_node *addr2inlines(const char
> > *dso_name, u64 addr,> 
> >  	INIT_LIST_HEAD(&node->val);
> >  	node->addr = addr;
> > 
> > -	if (!addr2line(dso_name, addr, NULL, NULL, dso, TRUE, node, sym))
> > -		goto out_free_inline_node;
> > -
> > -	if (list_empty(&node->val))
> > -		goto out_free_inline_node;
> > -
> > -	return node;
> > -
> > -out_free_inline_node:
> > -	inline_node__delete(node);
> > -	return NULL;
> > +	addr2line(dso_name, addr, NULL, NULL, dso, TRUE, node, sym);
> > +        return node;
> 
> Whitespace demanged.
> 
> Also please use 'true' instead of 'TRUE' for consistency (I know this
> is not your fault).

Done for the next iteration of this series, thanks!

-- 
Milian Wolff | milian.wolff@...b.com | Senior Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
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