linux-kernel - Re: [PATCH 2/5] perf tools: Extract __perf_evlist__mmap

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Message-ID: <20160426133019.GF16708@kernel.org>
Date:	Tue, 26 Apr 2016 10:30:20 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Zefan Li <lizefan@...wei.com>, pi3orama@....com
Subject: Re: [PATCH 2/5] perf tools: Extract __perf_evlist__mmap_read()

Em Tue, Apr 26, 2016 at 02:28:55AM +0000, Wang Nan escreveu:
> Extract event reader to __perf_evlist__mmap_read(). Future commit will
> feed it with manually computed 'head' and 'old' pointers.
> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Zefan Li <lizefan@...wei.com>
> Cc: pi3orama@....com
> ---
>  tools/perf/util/evlist.c | 40 +++++++++++++++++++++++++---------------
>  1 file changed, 25 insertions(+), 15 deletions(-)
> 
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index 85271e5..3ee94b2 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -679,24 +679,15 @@ static struct perf_evsel *perf_evlist__event2evsel(struct perf_evlist *evlist,
>  	return NULL;
>  }
>  
> -union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
> +static union perf_event *
> +__perf_evlist__mmap_read(struct perf_mmap *md, bool overwrite, u64 head,
> +			 u64 old, u64 *prev)
>  {

Ok, now this is not a perf_evlist method anymore, see the first
parameter? It handles perf_mmap instances, so please rename it to:

static union perf_event *perf_mmap__read(struct perf_mmap *md, bool overwrite,
					 u64 head, u64 *prev)

And thanks for leaving the renaming of those variables to the next
patch, that eases reviewieng indeed.

> -	struct perf_mmap *md = &evlist->mmap[idx];
> -	u64 head;
> -	u64 old = md->prev;
>  
> +union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
> +{
> +	struct perf_mmap *md = &evlist->mmap[idx];
> +	u64 head;
> +	u64 old = md->prev;
> +
> +	if (!atomic_read(&md->refcnt))
> +		return NULL;
> +
> +	head = perf_mmap__read_head(md);
> +
> +	return __perf_evlist__mmap_read(md, evlist->overwrite, head,
> +					old, &md->prev);


See that perf_mmap__read_head()? It acts on a struct perf_mmap too, thus
the prefix. This will end up as:

	head = perf_mmap__read_head(md);

	return perf_mmap__read(md, evlist->overwrite, head, old, &md->prev);

And see below yet another perf_mmap method, perf_mmap__empty()

Regards,

- Arnaldo
> +}
> +
>  static bool perf_mmap__empty(struct perf_mmap *md)
>  {
>  	return perf_mmap__read_head(md) == md->prev && !md->auxtrace_mmap.base;
> -- 
> 1.8.3.4