Hi,
On 17/08/2022 08:10, lic121 wrote:
In PMD, cycle cost for each rxq is saved so that we know each rxq's
load. But rxq that doesn't receive a packet is skipped. In fact,
polling no-packet rxq costs cycles as well. In my test, 100w pps
rxq(vhostuser) cost cycles 87,553,850,086 while no-packet rxq costs
cycles 353,402,306.
In asign mode "group", ovs always pick the lowest load pmd. If we
have too many(let's say 100) no-packet rxqs, these rxqs will be
asigned to the same pmd. Because no load increase when a no-packet
rxq to pmd.
You are correct that the estimated pmd load would not be increased when
rxqs without measured load are assigned. For this reason rxqs without
measured load are not assigned to the pmd with lowest estimated load.
They are assigned to whichever (available) pmd has the lowest number of
rxqs assigned. Assigning this rxq will increase the number of rxqs on
that pmd and that will be factored in when deciding where to assign the
next rxq with no measured cycles.
The decision is made here:
https://github.com/openvswitch/ovs/blob/master/lib/dpif-netdev.c#L5760-L5766
There is also a few lines about it in this article:
https://developers.redhat.com/articles/2021/11/19/improve-multicore-scaling-open-vswitch-dpdk#the_group_rxq_to_pmd_assignment_type
If you are seeing a case where rxqs without load are not being assigned
in the intended way as above, please give more details.
thanks,
Kevin.
To avoid this, this patch count cycles for no-packet rxq as well.
Signed-off-by: lic121
---
lib/dpif-netdev.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index a45b460..b30a098 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -5335,8 +5335,8 @@ dp_netdev_process_rxq_port(struct dp_netdev_pmd_thread
*pmd,
dp_netdev_pmd_flush_output_packets(pmd, false);
} else {
-/* Discard cycles. */
-cycle_timer_stop(>perf_stats, );
+cycles = cycle_timer_stop(>perf_stats, );
+dp_netdev_rxq_add_cycles(rxq, RXQ_CYCLES_PROC_CURR, cycles);
if (error != EAGAIN && error != EOPNOTSUPP) {
static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
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