linux-kernel - Re: [PATCH v7 2/2]: perf record: enable asynchronous trace writing

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Date:   Thu, 6 Sep 2018 13:04:18 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 2/2]: perf record: enable asynchronous trace writing

On Wed, Sep 05, 2018 at 10:39:25AM +0300, Alexey Budankov wrote:

SNIP

> diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
> index 384d17cd1379..1d57d8387caf 100644
> --- a/tools/perf/util/mmap.c
> +++ b/tools/perf/util/mmap.c
> @@ -332,12 +332,12 @@ int perf_mmap__read_init(struct perf_mmap *map)
>  	return __perf_mmap__read_init(map);
>  }
>  
> -int perf_mmap__push(struct perf_mmap *md, void *to,
> -		    int push(void *to, void *buf, size_t size))
> +int perf_mmap__push(struct perf_mmap *md, void *to, int idx,
> +		    int push(void *to, struct aiocb *cblock, void *data, size_t size))
>  {
>  	u64 head = perf_mmap__read_head(md);
>  	unsigned char *data = md->base + page_size;
> -	unsigned long size;
> +	unsigned long size, size0 = 0;
>  	void *buf;
>  	int rc = 0;
>  
> @@ -345,31 +345,58 @@ int perf_mmap__push(struct perf_mmap *md, void *to,
>  	if (rc < 0)
>  		return (rc == -EAGAIN) ? 0 : -1;
>  
> +	/* md->base data is copied into md->data[idx] buffer to
> +	 * release space in the kernel buffer as fast as possible,

please start the comment with the extra '/*', like:

	/*
	 * md->base data is copied into md->data[idx] buffer to
	 * release space in the kernel buffer as fast as possible,
	...

jirka