pmd reloads are currently serialised in each steps calling reload_affected_pmds. Any pmd processing packets, waiting on a mutex etc... will make other pmd threads wait for a delay that can be undeterministic when syscalls adds up.
Switch to a little busy loop on the control thread using the existing per-pmd reload boolean. The memory order on this atomic is rel-acq to have an explicit synchronisation between the pmd threads and the control thread. Signed-off-by: David Marchand <[email protected]> --- Changelog since v1: - removed the introduced reloading_pmds atomic and reuse the existing pmd->reload boolean as a single synchronisation point (Ilya) Changelog since RFC v1: - added memory ordering on 'reloading_pmds' atomic to serve as a synchronisation point between pmd threads and control thread --- lib/dpif-netdev.c | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-) diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c index b7f8117..b71fcbe 100644 --- a/lib/dpif-netdev.c +++ b/lib/dpif-netdev.c @@ -647,9 +647,6 @@ struct dp_netdev_pmd_thread { struct ovs_refcount ref_cnt; /* Every reference must be refcount'ed. */ struct cmap_node node; /* In 'dp->poll_threads'. */ - pthread_cond_t cond; /* For synchronizing pmd thread reload. */ - struct ovs_mutex cond_mutex; /* Mutex for condition variable. */ - /* Per thread exact-match cache. Note, the instance for cpu core * NON_PMD_CORE_ID can be accessed by multiple threads, and thusly * need to be protected by 'non_pmd_mutex'. Every other instance @@ -1754,11 +1751,8 @@ dp_netdev_reload_pmd__(struct dp_netdev_pmd_thread *pmd) return; } - ovs_mutex_lock(&pmd->cond_mutex); seq_change(pmd->reload_seq); atomic_store_explicit(&pmd->reload, true, memory_order_release); - ovs_mutex_cond_wait(&pmd->cond, &pmd->cond_mutex); - ovs_mutex_unlock(&pmd->cond_mutex); } static uint32_t @@ -4643,6 +4637,16 @@ rxq_scheduling(struct dp_netdev *dp, bool pinned) OVS_REQUIRES(dp->port_mutex) } static void +wait_reloading_pmd(struct dp_netdev_pmd_thread *pmd) +{ + bool reload; + + do { + atomic_read_explicit(&pmd->reload, &reload, memory_order_acquire); + } while (reload); +} + +static void reload_affected_pmds(struct dp_netdev *dp) { struct dp_netdev_pmd_thread *pmd; @@ -4651,6 +4655,12 @@ reload_affected_pmds(struct dp_netdev *dp) if (pmd->need_reload) { flow_mark_flush(pmd); dp_netdev_reload_pmd__(pmd); + } + } + + CMAP_FOR_EACH (pmd, node, &dp->poll_threads) { + if (pmd->need_reload) { + wait_reloading_pmd(pmd); pmd->need_reload = false; } } @@ -5816,11 +5826,8 @@ dpif_netdev_enable_upcall(struct dpif *dpif) static void dp_netdev_pmd_reload_done(struct dp_netdev_pmd_thread *pmd) { - ovs_mutex_lock(&pmd->cond_mutex); - atomic_store_relaxed(&pmd->reload, false); pmd->last_reload_seq = seq_read(pmd->reload_seq); - xpthread_cond_signal(&pmd->cond); - ovs_mutex_unlock(&pmd->cond_mutex); + atomic_store_explicit(&pmd->reload, false, memory_order_release); } /* Finds and refs the dp_netdev_pmd_thread on core 'core_id'. Returns @@ -5905,8 +5912,6 @@ dp_netdev_configure_pmd(struct dp_netdev_pmd_thread *pmd, struct dp_netdev *dp, pmd->reload_seq = seq_create(); pmd->last_reload_seq = seq_read(pmd->reload_seq); atomic_init(&pmd->reload, false); - xpthread_cond_init(&pmd->cond, NULL); - ovs_mutex_init(&pmd->cond_mutex); ovs_mutex_init(&pmd->flow_mutex); ovs_mutex_init(&pmd->port_mutex); cmap_init(&pmd->flow_table); @@ -5949,8 +5954,6 @@ dp_netdev_destroy_pmd(struct dp_netdev_pmd_thread *pmd) cmap_destroy(&pmd->flow_table); ovs_mutex_destroy(&pmd->flow_mutex); seq_destroy(pmd->reload_seq); - xpthread_cond_destroy(&pmd->cond); - ovs_mutex_destroy(&pmd->cond_mutex); ovs_mutex_destroy(&pmd->port_mutex); free(pmd); } @@ -5971,6 +5974,7 @@ dp_netdev_del_pmd(struct dp_netdev *dp, struct dp_netdev_pmd_thread *pmd) } else { atomic_store_relaxed(&pmd->exit, true); dp_netdev_reload_pmd__(pmd); + wait_reloading_pmd(pmd); xpthread_join(pmd->thread, NULL); } -- 1.8.3.1 _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
