linux-kernel - Re: [PATCH perf/core v5 05/15] perf probe: Use cache entry if possible

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Date:	Thu, 28 Apr 2016 11:47:53 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Masami Hiramatsu <mhiramat@...nel.org>
CC:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	<linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Hemant Kumar <hemant@...ux.vnet.ibm.com>,
	Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>
Subject: Re: [PATCH perf/core v5 05/15] perf probe: Use cache entry if
 possible

On Thu, Apr 28, 2016 at 03:37:52AM +0900, Masami Hiramatsu wrote:
> From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> 
> Before analyzing debuginfo, try to find a corresponding entry
> from probe cache always. This does not depend on --cache,
> the --cache enables to store/update cache, but looking up
> the cache is always enabled.
> 
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---

[SNIP]
> +static int find_probe_trace_events_from_cache(struct perf_probe_event *pev,
> +					      struct probe_trace_event **tevs)
> +{
> +	struct probe_cache *cache;
> +	struct probe_cache_entry *entry;
> +	struct probe_trace_event *tev;
> +	struct str_node *node;
> +	int ret, i;
> +
> +	cache = probe_cache__new(pev->target);
> +	if (!cache)
> +		return 0;
> +
> +	entry = probe_cache__find(cache, pev);
> +
> +	if (!entry && !pev->event &&
> +	    (!pev->point.file && pev->point.function && !pev->point.retprobe &&
> +	     !pev->point.line && !pev->point.offset && !pev->point.lazy_line)) {
> +		entry = probe_cache__find_by_name(cache, pev->group,
> +						  pev->point.function);
> +	}

What about arguments?  It seems that it only checks group and event
names of the given pev and use the cached entry's tev if found.  What
if they have different argument spec?

Thanks,
Namhyung


> +	if (!entry) {
> +		ret = 0;
> +		goto out;
> +	}
> +
> +	ret = strlist__nr_entries(entry->tevlist);
> +	if (ret > probe_conf.max_probes) {
> +		pr_debug("Too many entries matched in the cache of %s\n",
> +			 pev->target ? : "kernel");
> +		ret = -E2BIG;
> +		goto out;
> +	}
> +
> +	*tevs = zalloc(ret * sizeof(*tev));
> +	if (!*tevs) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
> +	i = 0;
> +	strlist__for_each(node, entry->tevlist) {
> +		tev = &(*tevs)[i++];
> +		ret = parse_probe_trace_command(node->s, tev);
> +		if (ret < 0)
> +			goto out;
> +		/* Set the uprobes attribute as same as original */
> +		tev->uprobes = pev->uprobes;
> +	}
> +	ret = i;
> +
> +out:
> +	probe_cache__delete(cache);
> +	return ret;
> +}