linux-kernel - Re: [PATCH 2/2] perf tools: Increase MAX_EVENT

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Date:	Thu, 17 Sep 2009 11:13:47 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Li Zefan <lizf@...fujitsu.com>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] perf tools: Increase MAX_EVENT_LENGTH

On Thu, Sep 17, 2009 at 11:08:34AM +0200, Peter Zijlstra wrote:
> On Thu, 2009-09-17 at 11:02 +0200, Frederic Weisbecker wrote:
> > On Thu, Sep 17, 2009 at 04:34:51PM +0800, Li Zefan wrote:
> > > The name length of some trace events is longer than 30, like
> > > sys_enter_sched_get_priority_max and ext4_mb_discard_preallocations.
> > > 
> > > Passing those events to perf-record will fail, try:
> > > 
> > >   # ./perf record -f -e syscalls:sys_enter_sched_get_priority_max -F 1 -a
> > > 
> > > Signed-off-by: Li Zefan <lizf@...fujitsu.com>
> > > ---
> > >  tools/perf/util/parse-events.c |    2 +-
> > >  1 files changed, 1 insertions(+), 1 deletions(-)
> > > 
> > > diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> > > index 034245e..c9ef944 100644
> > > --- a/tools/perf/util/parse-events.c
> > > +++ b/tools/perf/util/parse-events.c
> > > @@ -145,7 +145,7 @@ static int tp_event_has_id(struct dirent *sys_dir, struct dirent *evt_dir)
> > >  	   (strcmp(evt_dirent.d_name, "..")) &&				       \
> > >  	   (!tp_event_has_id(&sys_dirent, &evt_dirent)))
> > >  
> > > -#define MAX_EVENT_LENGTH 30
> > > +#define MAX_EVENT_LENGTH 40
> 
> This is userspace, is there any reason to be cheap with memory like
> this?
> 
> Why not stick in 1024 and be done for a while?
> 


Indeed, we may need to go even further than 40 in the future.
But I guess 512 would be already sufficient.

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