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service: avoid false sharing on core state

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For a valid service, the core mask of the service
is checked against the current core and the corresponding
entry in the active_on_lcore array is set or reset.

Upto 8 cores share the same cache line for their
service active_on_lcore array entries since each entry is a uint8_t.
Some number of these entries also share the cache line with
the internal_flags member of struct rte_service_spec_impl,
hence this false sharing also makes the service_valid() check
expensive.

Eliminate false sharing by moving the active_on_lcore array to
a per-core data structure. The array is now indexed by service id.

Signed-off-by: Nikhil Rao <nikhil.rao@intel.com>
Acked-by: Gage Eads <gage.eads@intel.com>
Acked-by: Harry van Haaren <harry.van.haaren@intel.com>
This commit is contained in:
Nikhil Rao 2019-09-16 15:31:02 +05:30 committed by David Marchand
parent c1077933d4
commit e484ccddbe
1 changed files with 7 additions and 9 deletions
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16
lib/librte_eal/common/rte_service.c
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@ -51,7 +51,6 @@ struct rte_service_spec_impl {
rte_atomic32_t num_mapped_cores;
uint64_t calls;
uint64_t cycles_spent;
uint8_t active_on_lcore[RTE_MAX_LCORE];
} __rte_cache_aligned;
/* the internal values of a service core */
@ -60,7 +59,7 @@ struct core_state {
uint64_t service_mask;
uint8_t runstate; /* running or stopped */
uint8_t is_service_core; /* set if core is currently a service core */
uint8_t service_active_on_lcore[RTE_SERVICE_NUM_MAX];
uint64_t loops;
uint64_t calls_per_service[RTE_SERVICE_NUM_MAX];
} __rte_cache_aligned;
@ -344,7 +343,7 @@ rte_service_runner_do_callback(struct rte_service_spec_impl *s,
static inline int32_t
service_run(uint32_t i, int lcore, struct core_state *cs, uint64_t service_mask)
service_run(uint32_t i, struct core_state *cs, uint64_t service_mask)
{
if (!service_valid(i))
return -EINVAL;
@ -352,11 +351,11 @@ service_run(uint32_t i, int lcore, struct core_state *cs, uint64_t service_mask)
if (s->comp_runstate != RUNSTATE_RUNNING ||
s->app_runstate != RUNSTATE_RUNNING ||
!(service_mask & (UINT64_C(1) << i))) {
s->active_on_lcore[lcore] = 0;
cs->service_active_on_lcore[i] = 0;
return -ENOEXEC;
}
s->active_on_lcore[lcore] = 1;
cs->service_active_on_lcore[i] = 1;
/* check do we need cmpset, if MT safe or <= 1 core
* mapped, atomic ops are not required.
@ -379,7 +378,6 @@ int32_t
rte_service_may_be_active(uint32_t id)
{
uint32_t ids[RTE_MAX_LCORE] = {0};
struct rte_service_spec_impl *s = &rte_services[id];
int32_t lcore_count = rte_service_lcore_list(ids, RTE_MAX_LCORE);
int i;
@ -387,7 +385,7 @@ rte_service_may_be_active(uint32_t id)
return -EINVAL;
for (i = 0; i < lcore_count; i++) {
if (s->active_on_lcore[ids[i]])
if (lcore_states[i].service_active_on_lcore[id])
return 1;
}
@ -418,7 +416,7 @@ rte_service_run_iter_on_app_lcore(uint32_t id, uint32_t serialize_mt_unsafe)
return -EBUSY;
}
int ret = service_run(id, rte_lcore_id(), cs, UINT64_MAX);
int ret = service_run(id, cs, UINT64_MAX);
if (serialize_mt_unsafe)
rte_atomic32_dec(&s->num_mapped_cores);
@ -439,7 +437,7 @@ rte_service_runner_func(void *arg)
for (i = 0; i < RTE_SERVICE_NUM_MAX; i++) {
/* return value ignored as no change to code flow */
service_run(i, lcore, cs, service_mask);
service_run(i, cs, service_mask);
}
cs->loops++;