Re: [dpdk-dev] [PATCH 1/2] service: add function for app lcore to run service

[Pavan Nikhilesh Bhagavatula <pbhagavatula@caviumnetworks.com>]

On Mon, Oct 23, 2017 at 06:16:51PM +0100, Harry van Haaren wrote:
> This commit adds a new function which allows an application lcore
> (aka; *not* a dedicated service-lcore) to run a service. This
> function is required to allow applications to gradually port
> functionality to using services, while still being able to run
> ordinary application functions.
>
> This requirement became clear when a patch to the existing
> eventdev/pipeline sample app was modified to use a service-core
> for scheduling - and that same core should be capable of running
> the "worker()" function from the application too.
>
> This patch refactors the existing running code into a smaller
> "service_run" function, which can be called by the dedicated
> service-core loop, and the newly added function.
>
> Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
>
> [1] http://dpdk.org/ml/archives/dev/2017-October/079876.html
> ---
>  lib/librte_eal/bsdapp/eal/rte_eal_version.map   |  1 +
>  lib/librte_eal/common/include/rte_service.h     | 21 +++++++++
>  lib/librte_eal/common/rte_service.c             | 59 ++++++++++++++++---------
>  lib/librte_eal/linuxapp/eal/rte_eal_version.map |  1 +
>  4 files changed, 61 insertions(+), 21 deletions(-)
>
> diff --git a/lib/librte_eal/bsdapp/eal/rte_eal_version.map b/lib/librte_eal/bsdapp/eal/rte_eal_version.map
> index 080896f..ee8dc98 100644
> --- a/lib/librte_eal/bsdapp/eal/rte_eal_version.map
> +++ b/lib/librte_eal/bsdapp/eal/rte_eal_version.map
> @@ -229,6 +229,7 @@ EXPERIMENTAL {
>  	rte_service_map_lcore_set;
>  	rte_service_probe_capability;
>  	rte_service_reset;
> +	rte_service_run_iter_on_app_lcore;
>  	rte_service_runstate_get;
>  	rte_service_runstate_set;
>  	rte_service_set_stats_enable;
> diff --git a/lib/librte_eal/common/include/rte_service.h b/lib/librte_eal/common/include/rte_service.h
> index 21da739..63d3170 100644
> --- a/lib/librte_eal/common/include/rte_service.h
> +++ b/lib/librte_eal/common/include/rte_service.h
> @@ -211,6 +211,27 @@ int32_t rte_service_runstate_get(uint32_t id);
>   * @warning
>   * @b EXPERIMENTAL: this API may change without prior notice
>   *
> + * This function runs a service callback from a non-service lcore context.
> + * The *id* of the service to be run is passed in, and the service-callback
> + * is executed on the calling lcore immediately if possible. If the service is
> + * not multi-thread capable and another thread is currently executing it, this
> + * function returns without running the callback.
> + *
> + * Note that any thread calling this function MUST be a DPDK EAL thread, as
> + * the *rte_lcore_id* function is used to access internal data structures.
> + *
> + * @retval 0 Service was run on the calling thread successfully
> + * @retval -EBUSY Another lcore is executing the service, and it is not a
> + *         multi-thread safe service, so the service was not run on this lcore
> + * @retval -ENOEXEC Service is not in a runnable state
> + * @retval -EINVAL Invalid service id
> + */
> +int32_t rte_service_run_iter_on_app_lcore(uint32_t id);
> +
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice
> + *
>   * Start a service core.
>   *
>   * Starting a core makes the core begin polling. Any services assigned to it
> diff --git a/lib/librte_eal/common/rte_service.c b/lib/librte_eal/common/rte_service.c
> index e598e16..4e27f75 100644
> --- a/lib/librte_eal/common/rte_service.c
> +++ b/lib/librte_eal/common/rte_service.c
> @@ -331,6 +331,42 @@ rte_service_runner_do_callback(struct rte_service_spec_impl *s,
>  		s->spec.callback(userdata);
>  }
>
> +
> +static inline int32_t
> +service_run(uint32_t i, struct core_state *cs, uint64_t service_mask)
> +{
> +	if (!service_valid(i))
> +		return -EINVAL;
> +	struct rte_service_spec_impl *s = &rte_services[i];
> +	if (s->comp_runstate != RUNSTATE_RUNNING ||
> +			s->app_runstate != RUNSTATE_RUNNING ||
> +			!(service_mask & (UINT64_C(1) << i)))
> +		return -ENOEXEC;
> +
> +	/* check do we need cmpset, if MT safe or <= 1 core
> +	 * mapped, atomic ops are not required.
> +	 */
> +	const int use_atomics = (service_mt_safe(s) == 0) &&
> +				(s->num_mapped_cores > 1);
> +	if (use_atomics) {
> +		if (!rte_atomic32_cmpset((uint32_t *)&s->execute_lock, 0, 1))
> +			return -EBUSY;
> +
> +		rte_service_runner_do_callback(s, cs, i);
> +		rte_atomic32_clear(&s->execute_lock);
> +	} else
> +		rte_service_runner_do_callback(s, cs, i);
> +
> +	return 0;
> +}
> +
> +int32_t rte_service_run_iter_on_app_lcore(uint32_t id)
> +{
> +	/* run service on calling core, using all-ones as the service mask */
> +	struct core_state *cs = &lcore_states[rte_lcore_id()];
> +	return service_run(id, cs, UINT64_MAX);
> +}
> +
>  static int32_t
>  rte_service_runner_func(void *arg)
>  {
> @@ -343,27 +379,8 @@ rte_service_runner_func(void *arg)
>  		const uint64_t service_mask = cs->service_mask;
>
>  		for (i = 0; i < RTE_SERVICE_NUM_MAX; i++) {
> -			if (!service_valid(i))
> -				continue;
> -			struct rte_service_spec_impl *s = &rte_services[i];
> -			if (s->comp_runstate != RUNSTATE_RUNNING ||
> -					s->app_runstate != RUNSTATE_RUNNING ||
> -					!(service_mask & (UINT64_C(1) << i)))
> -				continue;
> -
> -			/* check do we need cmpset, if MT safe or <= 1 core
> -			 * mapped, atomic ops are not required.
> -			 */
> -			const int use_atomics = (service_mt_safe(s) == 0) &&
> -						(s->num_mapped_cores > 1);
> -			if (use_atomics) {
> -				uint32_t *lock = (uint32_t *)&s->execute_lock;
> -				if (rte_atomic32_cmpset(lock, 0, 1)) {
> -					rte_service_runner_do_callback(s, cs, i);
> -					rte_atomic32_clear(&s->execute_lock);
> -				}
> -			} else
> -				rte_service_runner_do_callback(s, cs, i);
> +			/* return value ignored as no change to code flow */
> +			service_run(i, cs, service_mask);
>  		}
>
>  		rte_smp_rmb();
> diff --git a/lib/librte_eal/linuxapp/eal/rte_eal_version.map b/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> index c173ccf..c4d2c27 100644
> --- a/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> +++ b/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> @@ -233,6 +233,7 @@ EXPERIMENTAL {
>  	rte_service_map_lcore_set;
>  	rte_service_probe_capability;
>  	rte_service_reset;
> +	rte_service_run_iter_on_app_lcore;
>  	rte_service_runstate_get;
>  	rte_service_runstate_set;
>  	rte_service_set_stats_enable;
> --
> 2.7.4
>
Acked-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>