On Wed, Jun 26, 2019 at 2:43 PM Ilya Maximets <[email protected]> wrote:
> 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. > Indeed, and then I can move the wait_reloading_pmd() code directly into reload_affected_pmds(). -- David Marchand _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
