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dpif-netdev: Set timer slack for PMD threads.

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The default Linux timer slack groups timer expires into 50 uS intervals.

With some traffic patterns this can mean that returning to process
packets after a sleep takes too long and packets are dropped.

Add a helper to util.c and set use it to reduce the timer slack
for PMD threads, so that sleeps with smaller resolutions can be done
to prevent sleeping for too long.

Fixes: de3bbdc479 ("dpif-netdev: Add PMD load based sleeping.")
Reported-at: https://mail.openvswitch.org/pipermail/ovs-dev/2023-January/401121.html
Reported-by: Ilya Maximets <i.maximets@ovn.org>
Signed-off-by: David Marchand <david.marchand@redhat.com>
Co-authored-by: Kevin Traynor <ktraynor@redhat.com>
Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
This commit is contained in:
David Marchand
2023-01-18 16:23:55 +00:00
committed by Ilya Maximets
parent e24b68fa70
commit f62629a558
4 changed files with 21 additions and 5 deletions
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4
lib/dpif-netdev.c
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@@ -171,6 +171,9 @@ static struct odp_support dp_netdev_support = {
/* Time in microseconds to try RCU quiescing. */
#define PMD_RCU_QUIESCE_INTERVAL 10000LL
/* Timer resolution for PMD threads in nanoseconds. */
#define PMD_TIMER_RES_NS 1000
/* Number of pkts Rx on an interface that will stop pmd thread sleeping. */
#define PMD_SLEEP_THRESH (NETDEV_MAX_BURST / 2)
/* Time in uS to increment a pmd thread sleep time. */
@@ -6962,6 +6965,7 @@ pmd_thread_main(void *f_)
poll_cnt = pmd_load_queues_and_ports(pmd, &poll_list);
dfc_cache_init(&pmd->flow_cache);
pmd_alloc_static_tx_qid(pmd);
set_timer_resolution(PMD_TIMER_RES_NS);
reload:
atomic_count_init(&pmd->pmd_overloaded, 0);