[lttng-dev] [PATCH lttng-ust] Implement LTTNG_UST_BLOCKING_RETRY_TIMEOUT

[Jonathan Rajotte Julien]

On 2016-11-04 10:22 AM, Philippe Proulx wrote:
> On Fri, Nov 4, 2016 at 10:13 AM, Jonathan Rajotte Julien
> <Jonathan.rajotte-julien at efficios.com> wrote:
>> Nitpicking:
>>
>> Should this be RETRY_DELAY_MS since other name scheme use the *_MS suffix ?
>>
>> e.g:
>> LTTNG_UST_RING_BUFFER_RETRY_DELAY_MS
>> CONFIG_LTTNG_UST_DEFAULT_BLOCKING_RETRY_TIMEOUT_MS
>> timeout_left_ms
> Counterexample: LTTNG_UST_REGISTER_TIMEOUT.
>
> Phil

Well we have a problem.

Jonathan
>
>>
>>>      /*
>>>     * Non-static to ensure the compiler does not optimize away the xor.
>>> @@ -149,6 +150,14 @@ static struct timer_signal_data timer_signal = {
>>>          .lock = PTHREAD_MUTEX_INITIALIZER,
>>>    };
>>>    +int lttng_ust_blocking_retry_timeout =
>>> +               CONFIG_LTTNG_UST_DEFAULT_BLOCKING_RETRY_TIMEOUT_MS;
>>> +
>>> +void lttng_ust_ringbuffer_set_retry_timeout(int timeout)
>>> +{
>>> +       lttng_ust_blocking_retry_timeout = timeout;
>>> +}
>>> +
>>>    /**
>>>     * lib_ring_buffer_reset - Reset ring buffer to initial values.
>>>     * @buf: Ring buffer.
>>> @@ -1985,6 +1994,23 @@ void lib_ring_buffer_switch_slow(struct
>>> lttng_ust_lib_ring_buffer *buf, enum swi
>>>          lib_ring_buffer_switch_old_end(buf, chan, &offsets, tsc, handle);
>>>    }
>>>    +static
>>> +bool handle_blocking_retry(int *timeout_left_ms)
>>> +{
>>> +       int timeout = *timeout_left_ms, delay;
>>> +
>>> +       if (caa_likely(!timeout))
>>> +               return false;   /* Do not retry, discard event. */
>>> +       if (timeout < 0)        /* Wait forever. */
>>> +               delay = RETRY_DELAY;
>>> +       else
>>> +               delay = min_t(int, timeout, RETRY_DELAY);
>>> +       (void) poll(NULL, 0, delay);
>>> +       if (timeout > 0)
>>> +               *timeout_left_ms -= delay;
>>> +       return true;    /* Retry. */
>>> +}
>>> +
>>>    /*
>>>     * Returns :
>>>     * 0 if ok
>>> @@ -2001,6 +2027,7 @@ int lib_ring_buffer_try_reserve_slow(struct
>>> lttng_ust_lib_ring_buffer *buf,
>>>          const struct lttng_ust_lib_ring_buffer_config *config =
>>> &chan->backend.config;
>>>          struct lttng_ust_shm_handle *handle = ctx->handle;
>>>          unsigned long reserve_commit_diff, offset_cmp;
>>> +       int timeout_left_ms = lttng_ust_blocking_retry_timeout;
>>>      retry:
>>>          offsets->begin = offset_cmp = v_read(config, &buf->offset);
>>> @@ -2083,6 +2110,9 @@ retry:
>>>                                  >= chan->backend.buf_size)) {
>>>                                  unsigned long nr_lost;
>>>    +                             if
>>> (handle_blocking_retry(&timeout_left_ms))
>>> +                                       goto retry;
>>> +
>>>                                  /*
>>>                                   * We do not overwrite non consumed
>>> buffers
>>>                                   * and we are full : record is lost.
>>
>> --
>> Jonathan R. Julien
>> Efficios
>>
>>
>> _______________________________________________
>> lttng-dev mailing list
>> lttng-dev at lists.lttng.org
>> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

-- 
Jonathan R. Julien
Efficios