On 26.06.2019 12:08, David Marchand wrote: > 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);
Join will wait for the thread exit. We don't need to wait for reload here. > xpthread_join(pmd->thread, NULL); > } > > _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
