On 16.11.2016 03:46, Daniele Di Proietto wrote:
> There's no reason for a pmd thread to perform its main loop if there are
> no queues in its poll_list.
>
> This commit introduces a seq object on which the pmd thread can be
> blocked, if there are no queues.
>
> When the main thread wants to reload a pmd threads it must now change
> the seq object (in case it's blocked) and set 'reload' to true.
>
> This is useful to avoid wasting CPU cycles and is also necessary for a
> future commit.
>
> Signed-off-by: Daniele Di Proietto <[email protected]>
> ---
> lib/dpif-netdev.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index 23546b9..6c2ad29 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -485,6 +485,8 @@ struct dp_netdev_pmd_thread {
> unsigned long long last_cycles;
>
> struct latch exit_latch; /* For terminating the pmd thread. */
> + struct seq *reload_seq;
> + uint64_t last_reload_seq;
> atomic_bool reload; /* Do we need to reload ports? */
> pthread_t thread;
> unsigned core_id; /* CPU core id of this pmd thread. */
> @@ -1210,6 +1212,7 @@ dp_netdev_reload_pmd__(struct dp_netdev_pmd_thread *pmd)
> }
>
> ovs_mutex_lock(&pmd->cond_mutex);
> + seq_change(pmd->reload_seq);
> atomic_store_relaxed(&pmd->reload, true);
> ovs_mutex_cond_wait(&pmd->cond, &pmd->cond_mutex);
> ovs_mutex_unlock(&pmd->cond_mutex);
> @@ -3148,6 +3151,13 @@ reload:
> netdev_rxq_get_queue_id(poll_list[i].rx));
> }
>
> + if (!poll_cnt) {
> + while (seq_read(pmd->reload_seq) == pmd->last_reload_seq) {
> + seq_wait(pmd->reload_seq, pmd->last_reload_seq);
> + poll_block();
> + }
> + }
> +
How about putting the next polling loop under 'else'? This will help
to avoid 1024 empty cycles inside of it. Or, maybe, we can just set
'lc' to 1025 after the 'while' above.
Another thought: I guess, we should enter a quiescent state before
'while' loop and end it after.
Also, I prefer to merge 'reload' and 'reload_seq' somehow, but I don't
know how to do this yet.
> for (;;) {
> for (i = 0; i < poll_cnt; i++) {
> dp_netdev_process_rxq_port(pmd, poll_list[i].port,
> poll_list[i].rx);
> @@ -3223,6 +3233,7 @@ 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);
> }
> @@ -3317,6 +3328,8 @@ dp_netdev_configure_pmd(struct dp_netdev_pmd_thread
> *pmd, struct dp_netdev *dp,
>
> ovs_refcount_init(&pmd->ref_cnt);
> latch_init(&pmd->exit_latch);
> + 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);
> @@ -3356,6 +3369,7 @@ dp_netdev_destroy_pmd(struct dp_netdev_pmd_thread *pmd)
> cmap_destroy(&pmd->flow_table);
> ovs_mutex_destroy(&pmd->flow_mutex);
> latch_destroy(&pmd->exit_latch);
> + seq_destroy(pmd->reload_seq);
> xpthread_cond_destroy(&pmd->cond);
> ovs_mutex_destroy(&pmd->cond_mutex);
> ovs_mutex_destroy(&pmd->port_mutex);
>
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