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event/dsw: add port busy cycles xstats

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DSW keeps an internal port load estimate, used by the load balancing
mechanism. As a side effect, it keeps track of the total number of
busy cycles since startup. This metric is indirectly exposed in the
form of DSW xstats' "port_<n>_event_proc_latency", which is the total
number of busy cycles divided by the total number of events processed
on a particular port.

An external application can take (event_latency * dequeued) to go back
to busy_cycles. One reason for doing this is to measure the port's
load during a longer time period, without resorting to sampling
"port_<n>_load". However, as the number dequeued events grows, a
rounding error in event_latency renders the application-calculated
busy_cycles inaccurate.

Thus, it makes sense to directly expose the number of busy cycles as a
DSW xstats, even though it might seem redundant.

Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
This commit is contained in:
Mattias Rönnblom 2020-03-09 07:51:06 +01:00 committed by Jerin Jacob
parent cea7bc6713
commit b97d3a9cbc
1 changed files with 9 additions and 0 deletions
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9
drivers/event/dsw/dsw_xstats.c
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@ -109,6 +109,13 @@ dsw_xstats_port_get_event_proc_latency(struct dsw_evdev *dsw, uint8_t port_id,
return dequeued > 0 ? total_busy_cycles / dequeued : 0;
}
static uint64_t
dsw_xstats_port_get_busy_cycles(struct dsw_evdev *dsw, uint8_t port_id,
uint8_t queue_id __rte_unused)
{
return dsw->ports[port_id].total_busy_cycles;
}
DSW_GEN_PORT_ACCESS_FN(inflight_credits)
DSW_GEN_PORT_ACCESS_FN(pending_releases)
@ -147,6 +154,8 @@ static struct dsw_xstats_port dsw_port_xstats[] = {
false },
{ "port_%u_event_proc_latency", dsw_xstats_port_get_event_proc_latency,
false },
{ "port_%u_busy_cycles", dsw_xstats_port_get_busy_cycles,
false },
{ "port_%u_inflight_credits", dsw_xstats_port_get_inflight_credits,
false },
{ "port_%u_pending_releases", dsw_xstats_port_get_pending_releases,