linux-kernel - Re: [PATCH v2 14/15] perf record: start threads in the beginning of trace streaming

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Date:   Sat, 24 Oct 2020 17:44:16 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 14/15] perf record: start threads in the beginning of
 trace streaming

On Wed, Oct 21, 2020 at 07:10:09PM +0300, Alexey Budankov wrote:
> 
> Start threads in detached state because its management is possible
> via messaging. Block signals prior the threads start so only main
> tool thread would be notified on external async signals during data
> collection. Streaming threads connect one-to-one to mapped data
> buffers and write into per-CPU trace files located at data directory.
> Data buffers and threads are affined to local NUMA nodes and monitored
> CPUs according to system topology. --cpu option can be used to specify
> CPUs to be monitored.
> 
> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
> ---
>  tools/perf/builtin-record.c | 128 +++++++++++++++++++++++++++++++++---
>  1 file changed, 120 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index a15642656066..1d41e996a994 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -56,6 +56,7 @@
>  #include <poll.h>
>  #include <pthread.h>
>  #include <unistd.h>
> +#include <sys/syscall.h>
>  #include <sched.h>
>  #include <signal.h>
>  #ifdef HAVE_EVENTFD_SUPPORT
> @@ -1377,6 +1378,62 @@ static void record__thread_munmap_filtered(struct fdarray *fda, int fd,
>  		perf_mmap__put(map);
>  }
>  
> +static void *record__thread(void *arg)
> +{
> +	enum thread_msg msg = THREAD_MSG__READY;
> +	bool terminate = false;
> +	struct fdarray *pollfd;
> +	int err, ctlfd_pos;
> +
> +	thread = arg;
> +	thread->tid = syscall(SYS_gettid);
> +
> +	err = write(thread->comm.ack[1], &msg, sizeof(msg));
> +	if (err == -1)
> +		pr_err("threads: %d failed to notify on start. Error %m", thread->tid);
> +
> +	pollfd = &(thread->pollfd);

I don't think braces are necessary in here

jirka