Re: [PATCH RFC 2/6] perf dso: Refactor dso_cache__read()

From: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H . Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Mathieu Poirier <mathieu.poirier@linaro.org>,
	Leo Yan <leo.yan@linaro.org>, Jiri Olsa <jolsa@redhat.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC 2/6] perf dso: Refactor dso_cache__read()
Date: Fri, 25 Oct 2019 11:54:00 -0300	[thread overview]
Message-ID: <20191025145400.GB24735@kernel.org> (raw)
In-Reply-To: <20191025130000.13032-3-adrian.hunter@intel.com>

Em Fri, Oct 25, 2019 at 03:59:56PM +0300, Adrian Hunter escreveu:
> Refactor dso_cache__read() to separate populating the cache from copying
> data from it.  This is preparation for adding a cache "write" that will
> update the data in the cache.

Ditto for 2/6 and 3/6, i.e. applying them now.

- Arnaldo
 
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
>  tools/perf/util/dso.c | 64 +++++++++++++++++++++++++------------------
>  1 file changed, 37 insertions(+), 27 deletions(-)
> 
> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> index e11ddf86f2b3..460330d125b6 100644
> --- a/tools/perf/util/dso.c
> +++ b/tools/perf/util/dso.c
> @@ -768,7 +768,7 @@ dso_cache__free(struct dso *dso)
>  	pthread_mutex_unlock(&dso->lock);
>  }
>  
> -static struct dso_cache *dso_cache__find(struct dso *dso, u64 offset)
> +static struct dso_cache *__dso_cache__find(struct dso *dso, u64 offset)
>  {
>  	const struct rb_root *root = &dso->data.cache;
>  	struct rb_node * const *p = &root->rb_node;
> @@ -863,54 +863,64 @@ static ssize_t file_read(struct dso *dso, struct machine *machine,
>  	return ret;
>  }
>  
> -static ssize_t
> -dso_cache__read(struct dso *dso, struct machine *machine,
> -		u64 offset, u8 *data, ssize_t size)
> +static struct dso_cache *dso_cache__populate(struct dso *dso,
> +					     struct machine *machine,
> +					     u64 offset, ssize_t *ret)
>  {
>  	u64 cache_offset = offset & DSO__DATA_CACHE_MASK;
>  	struct dso_cache *cache;
>  	struct dso_cache *old;
> -	ssize_t ret;
>  
>  	cache = zalloc(sizeof(*cache) + DSO__DATA_CACHE_SIZE);
> -	if (!cache)
> -		return -ENOMEM;
> +	if (!cache) {
> +		*ret = -ENOMEM;
> +		return NULL;
> +	}
>  
>  	if (dso->binary_type == DSO_BINARY_TYPE__BPF_PROG_INFO)
> -		ret = bpf_read(dso, cache_offset, cache->data);
> +		*ret = bpf_read(dso, cache_offset, cache->data);
>  	else
> -		ret = file_read(dso, machine, cache_offset, cache->data);
> +		*ret = file_read(dso, machine, cache_offset, cache->data);
>  
> -	if (ret > 0) {
> -		cache->offset = cache_offset;
> -		cache->size   = ret;
> +	if (*ret <= 0) {
> +		free(cache);
> +		return NULL;
> +	}
>  
> -		old = dso_cache__insert(dso, cache);
> -		if (old) {
> -			/* we lose the race */
> -			free(cache);
> -			cache = old;
> -		}
> +	cache->offset = cache_offset;
> +	cache->size   = *ret;
>  
> -		ret = dso_cache__memcpy(cache, offset, data, size);
> +	old = dso_cache__insert(dso, cache);
> +	if (old) {
> +		/* we lose the race */
> +		free(cache);
> +		cache = old;
>  	}
>  
> -	if (ret <= 0)
> -		free(cache);
> +	return cache;
> +}
>  
> -	return ret;
> +static struct dso_cache *dso_cache__find(struct dso *dso,
> +					 struct machine *machine,
> +					 u64 offset,
> +					 ssize_t *ret)
> +{
> +	struct dso_cache *cache = __dso_cache__find(dso, offset);
> +
> +	return cache ? cache : dso_cache__populate(dso, machine, offset, ret);
>  }
>  
>  static ssize_t dso_cache_read(struct dso *dso, struct machine *machine,
>  			      u64 offset, u8 *data, ssize_t size)
>  {
>  	struct dso_cache *cache;
> +	ssize_t ret = 0;
>  
> -	cache = dso_cache__find(dso, offset);
> -	if (cache)
> -		return dso_cache__memcpy(cache, offset, data, size);
> -	else
> -		return dso_cache__read(dso, machine, offset, data, size);
> +	cache = dso_cache__find(dso, machine, offset, &ret);
> +	if (!cache)
> +		return ret;
> +
> +	return dso_cache__memcpy(cache, offset, data, size);
>  }
>  
>  /*
> -- 
> 2.17.1

-- 

- Arnaldo