linux-kernel - Re: [PATCH v2 36/40] tracing: Remove lookups from tracing

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Message-ID: <1505225771.1331.3.camel@tzanussi-mobl.amr.corp.intel.com>
Date:   Tue, 12 Sep 2017 09:16:11 -0500
From:   Tom Zanussi <tom.zanussi@...ux.intel.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     rostedt@...dmis.org, tglx@...utronix.de, namhyung@...nel.org,
        vedang.patel@...el.com, bigeasy@...utronix.de,
        joel.opensrc@...il.com, joelaf@...gle.com,
        mathieu.desnoyers@...icios.com, baohong.liu@...el.com,
        linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH v2 36/40] tracing: Remove lookups from tracing_map
 hitcount

Hi Masami,

On Tue, 2017-09-12 at 11:16 +0900, Masami Hiramatsu wrote:
> Hi Tom,
> 
> On Tue,  5 Sep 2017 16:57:48 -0500
> Tom Zanussi <tom.zanussi@...ux.intel.com> wrote:
> 
> > Lookups inflate the hitcount, making it essentially useless.  Only
> > inserts and updates should really affect the hitcount anyway, so
> > explicitly filter lookups out.
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
> > ---
> >  kernel/trace/tracing_map.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c
> > index a4e5a56..f8e2338 100644
> > --- a/kernel/trace/tracing_map.c
> > +++ b/kernel/trace/tracing_map.c
> > @@ -538,7 +538,8 @@ static inline bool keys_match(void *key, void *test_key, unsigned key_size)
> >  		if (test_key && test_key == key_hash) {
> >  			if (entry->val &&
> >  			    keys_match(key, entry->val->key, map->key_size)) {
> > -				atomic64_inc(&map->hits);
> > +				if (!lookup_only)
> > +					atomic64_inc(&map->hits);
> 
> Is this a kind of bugfix for current code?
> If so, such patch can be posted in separate series.
> 

Yeah, that sounds like a good idea - will separate this out along with
another one or two in the same boat..

Thanks,

Tom