linux-kernel - Re: [PATCH v2 1/2]: perf util: map data buffer for preserving collected data

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Date:   Mon, 27 Aug 2018 10:28:19 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.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>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2 1/2]: perf util: map data buffer for preserving
 collected data

On Thu, Aug 23, 2018 at 07:42:09PM +0300, Alexey Budankov wrote:
> 
> The data buffer and accompanying AIO control block are allocated at 
> perf_mmap object and the mapped data buffer size is equal to 
> the kernel one.
> 
> The buffer is then used to preserve profiling data ready for dumping 
> and queue it for asynchronous writing into perf trace thru implemented 
> record__aio_write() function.
> 
> mmap_aio control structure of the size equal to the number of per-cpu 
> kernel buffers is used to keep pointers to enqueued AIO control 
> blocks for monitoring of completed AIO operations.
> 
> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
> ---
> Changes in v2:
> - converted zalloc() to calloc() for allocation of mmap_aio array,
> - cleared typo and adjusted fallback branch code;
> ---
> tools/perf/builtin-record.c | 18 ++++++++++++++++++
>  tools/perf/util/evlist.c    |  7 +++++++
>  tools/perf/util/evlist.h    |  2 ++
>  tools/perf/util/mmap.c      | 12 ++++++++++++
>  tools/perf/util/mmap.h      |  3 +++
>  5 files changed, 42 insertions(+)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 22ebeb92ac51..a35675e9f3aa 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -53,6 +53,7 @@
>  #include <sys/mman.h>
>  #include <sys/wait.h>
>  #include <linux/time64.h>
> +#include <aio.h>
>  
>  struct switch_output {
>  	bool		 enabled;
> @@ -121,6 +122,23 @@ static int record__write(struct record *rec, void *bf, size_t size)
>  	return 0;
>  }
>  
> +static int record__aio_write(int trace_fd, struct aiocb *cblock,
> +		void *buf, size_t size, off_t off)
> +{

this breaks bisection:

builtin-record.c:125:12: error: ‘record__aio_write’ defined but not used [-Werror=unused-function]
 static int record__aio_write(int trace_fd, struct aiocb *cblock,

jirka