[dpdk-dev] [PATCH v2 1/2] eal: add API that sleeps while waiting for threads
Ananyev, Konstantin
konstantin.ananyev at intel.com
Tue Oct 16 10:42:42 CEST 2018
HI Ferruh,
> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Ferruh Yigit
> Sent: Monday, October 15, 2018 11:21 PM
> To: Richardson, Bruce <bruce.richardson at intel.com>
> Cc: dev at dpdk.org; Yigit, Ferruh <ferruh.yigit at intel.com>; stephen at networkplumber.org
> Subject: [dpdk-dev] [PATCH v2 1/2] eal: add API that sleeps while waiting for threads
>
> It is common that sample applications call rte_eal_wait_lcore() while
> waiting for worker threads to be terminated.
> Mostly master lcore keeps waiting in this function.
>
> The waiting app for termination is not a time critical task, app can
> prefer a sleep version of the waiting to consume less cycles.
>
> A sleeping version of the API, rte_eal_wait_lcore_sleep(), has been
> added which uses pthread conditions.
>
> Sample applications will be updated later to use this API.
>
> Signed-off-by: Ferruh Yigit <ferruh.yigit at intel.com>
> ---
> v2:
> * use pthread cond instead of usleep
> ---
> lib/librte_eal/bsdapp/eal/eal.c | 3 +++
> lib/librte_eal/bsdapp/eal/eal_thread.c | 7 ++++++
> lib/librte_eal/common/eal_common_launch.c | 22 ++++++++++++++++++
> lib/librte_eal/common/include/rte_launch.h | 26 ++++++++++++++++++++++
> lib/librte_eal/common/include/rte_lcore.h | 3 +++
> lib/librte_eal/linuxapp/eal/eal.c | 3 +++
> lib/librte_eal/linuxapp/eal/eal_thread.c | 7 ++++++
> lib/librte_eal/rte_eal_version.map | 1 +
> 8 files changed, 72 insertions(+)
>
> diff --git a/lib/librte_eal/bsdapp/eal/eal.c b/lib/librte_eal/bsdapp/eal/eal.c
> index 7735194a3..e7d676657 100644
> --- a/lib/librte_eal/bsdapp/eal/eal.c
> +++ b/lib/librte_eal/bsdapp/eal/eal.c
> @@ -756,6 +756,9 @@ rte_eal_init(int argc, char **argv)
> snprintf(thread_name, sizeof(thread_name),
> "lcore-slave-%d", i);
> rte_thread_setname(lcore_config[i].thread_id, thread_name);
> +
> + pthread_mutex_init(&rte_eal_thread_mutex[i], NULL);
> + pthread_cond_init(&rte_eal_thread_cond[i], NULL);
> }
>
> /*
> diff --git a/lib/librte_eal/bsdapp/eal/eal_thread.c b/lib/librte_eal/bsdapp/eal/eal_thread.c
> index 309b58726..60db32d57 100644
> --- a/lib/librte_eal/bsdapp/eal/eal_thread.c
> +++ b/lib/librte_eal/bsdapp/eal/eal_thread.c
> @@ -28,6 +28,9 @@ RTE_DEFINE_PER_LCORE(unsigned, _lcore_id) = LCORE_ID_ANY;
> RTE_DEFINE_PER_LCORE(unsigned, _socket_id) = (unsigned)SOCKET_ID_ANY;
> RTE_DEFINE_PER_LCORE(rte_cpuset_t, _cpuset);
>
> +pthread_cond_t rte_eal_thread_cond[RTE_MAX_LCORE];
> +pthread_mutex_t rte_eal_thread_mutex[RTE_MAX_LCORE];
I think would be better to include cond and mutex into struct lcore_config itself,
probably would help to avoid false sharing.
Though yeh, it would mean ABI breakage, I suppose.
> +
> /*
> * Send a message to a slave lcore identified by slave_id to call a
> * function f with argument arg. Once the execution is done, the
> @@ -154,6 +157,10 @@ eal_thread_loop(__attribute__((unused)) void *arg)
> lcore_config[lcore_id].ret = ret;
> rte_wmb();
> lcore_config[lcore_id].state = FINISHED;
> +
> + pthread_mutex_lock(&rte_eal_thread_mutex[lcore_id]);
> + pthread_cond_signal(&rte_eal_thread_cond[lcore_id]);
> + pthread_mutex_unlock(&rte_eal_thread_mutex[lcore_id]);
I understand it would work that way too, but if you introduce mutex and cond around
the state, then it is better to manipulate/access the state after grabbing the mutex.
BTW in that case we don't need wmb:
lcore_config[lcore_id].ret = ret;
pthread_mutex_lock(...);
lcore_config[lcore_id].state = FINISHED;
pthread_cond_signal(..);
pthread_mutex_unlock(...);
Konstantin
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