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From: Andriy Berestovskyy <aber@semihalf.com>
To: dev@dpdk.org
Cc: remy.horton@intel.com
Date: Tue, 23 Jan 2018 16:43:16 +0100
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Subject: [dpdk-dev] [PATCH v2] keepalive: fix keepalive state alignment
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The __rte_cache_aligned was applied to the whole array,
not the array elements. This leads to a false sharing between
the monitored cores.
Fixes: e70a61ad50ab ("keepalive: export states")
Cc: remy.horton@intel.com
Signed-off-by: Andriy Berestovskyy <aber@semihalf.com>
---
Notes (changelog):
V2 Changes:
- fixed struct name
- fixed documentation
doc/guides/sample_app_ug/keep_alive.rst | 2 +-
lib/librte_eal/common/rte_keepalive.c | 28 ++++++++++++++++++----------
2 files changed, 19 insertions(+), 11 deletions(-)
diff --git a/doc/guides/sample_app_ug/keep_alive.rst b/doc/guides/sample_app_ug/keep_alive.rst
index 38856d2..27ed2a8 100644
--- a/doc/guides/sample_app_ug/keep_alive.rst
+++ b/doc/guides/sample_app_ug/keep_alive.rst
@@ -168,5 +168,5 @@ The rte_keepalive_mark_alive function simply sets the core state to alive.
static inline void
rte_keepalive_mark_alive(struct rte_keepalive *keepcfg)
{
- keepcfg->state_flags[rte_lcore_id()] = ALIVE;
+ keepcfg->live_data[rte_lcore_id()].core_state = RTE_KA_STATE_ALIVE;
}
diff --git a/lib/librte_eal/common/rte_keepalive.c b/lib/librte_eal/common/rte_keepalive.c
index 7ddf201..e0494b2 100644
--- a/lib/librte_eal/common/rte_keepalive.c
+++ b/lib/librte_eal/common/rte_keepalive.c
@@ -13,8 +13,12 @@
struct rte_keepalive {
/** Core Liveness. */
- enum rte_keepalive_state __rte_cache_aligned state_flags[
- RTE_KEEPALIVE_MAXCORES];
+ struct {
+ /*
+ * Each element must be cache aligned to prevent false sharing.
+ */
+ enum rte_keepalive_state core_state __rte_cache_aligned;
+ } live_data[RTE_KEEPALIVE_MAXCORES];
/** Last-seen-alive timestamps */
uint64_t last_alive[RTE_KEEPALIVE_MAXCORES];
@@ -67,19 +71,22 @@ rte_keepalive_dispatch_pings(__rte_unused void *ptr_timer,
if (keepcfg->active_cores[idx_core] == 0)
continue;
- switch (keepcfg->state_flags[idx_core]) {
+ switch (keepcfg->live_data[idx_core].core_state) {
case RTE_KA_STATE_UNUSED:
break;
case RTE_KA_STATE_ALIVE: /* Alive */
- keepcfg->state_flags[idx_core] = RTE_KA_STATE_MISSING;
+ keepcfg->live_data[idx_core].core_state =
+ RTE_KA_STATE_MISSING;
keepcfg->last_alive[idx_core] = rte_rdtsc();
break;
case RTE_KA_STATE_MISSING: /* MIA */
print_trace("Core MIA. ", keepcfg, idx_core);
- keepcfg->state_flags[idx_core] = RTE_KA_STATE_DEAD;
+ keepcfg->live_data[idx_core].core_state =
+ RTE_KA_STATE_DEAD;
break;
case RTE_KA_STATE_DEAD: /* Dead */
- keepcfg->state_flags[idx_core] = RTE_KA_STATE_GONE;
+ keepcfg->live_data[idx_core].core_state =
+ RTE_KA_STATE_GONE;
print_trace("Core died. ", keepcfg, idx_core);
if (keepcfg->callback)
keepcfg->callback(
@@ -90,7 +97,8 @@ rte_keepalive_dispatch_pings(__rte_unused void *ptr_timer,
case RTE_KA_STATE_GONE: /* Buried */
break;
case RTE_KA_STATE_DOZING: /* Core going idle */
- keepcfg->state_flags[idx_core] = RTE_KA_STATE_SLEEP;
+ keepcfg->live_data[idx_core].core_state =
+ RTE_KA_STATE_SLEEP;
keepcfg->last_alive[idx_core] = rte_rdtsc();
break;
case RTE_KA_STATE_SLEEP: /* Idled core */
@@ -100,7 +108,7 @@ rte_keepalive_dispatch_pings(__rte_unused void *ptr_timer,
keepcfg->relay_callback(
keepcfg->relay_callback_data,
idx_core,
- keepcfg->state_flags[idx_core],
+ keepcfg->live_data[idx_core].core_state,
keepcfg->last_alive[idx_core]
);
}
@@ -144,11 +152,11 @@ rte_keepalive_register_core(struct rte_keepalive *keepcfg, const int id_core)
void
rte_keepalive_mark_alive(struct rte_keepalive *keepcfg)
{
- keepcfg->state_flags[rte_lcore_id()] = RTE_KA_STATE_ALIVE;
+ keepcfg->live_data[rte_lcore_id()].core_state = RTE_KA_STATE_ALIVE;
}
void
rte_keepalive_mark_sleep(struct rte_keepalive *keepcfg)
{
- keepcfg->state_flags[rte_lcore_id()] = RTE_KA_STATE_DOZING;
+ keepcfg->live_data[rte_lcore_id()].core_state = RTE_KA_STATE_DOZING;
}
--
2.7.4