On 3/18/2019 1:48 PM, Jan Scheurich wrote:
Hi Ilya,
Thanks for spotting this. I believe your fix is correct.
BR, Jan
-----Original Message-----
From: Ilya Maximets <[email protected]>
Sent: Monday, 18 March, 2019 14:01
To: [email protected]; Ian Stokes <[email protected]>
Cc: Kevin Traynor <[email protected]>; Ilya Maximets
<[email protected]>; Jan Scheurich <[email protected]>
Subject: [PATCH] dpif-netdev-perf: Fix double update of perf histograms.
Real values of 'packets per batch' and 'cycles per upcall' already added to
histograms in 'dpif-netdev' on receive. Adding the averages makes statistics
wrong. We should not add to histograms values that never really appeared.
For exmaple, in current code following situation is possible:
pmd thread numa_id 0 core_id 5:
...
Rx packets: 83 (0 Kpps, 13873 cycles/pkt)
...
- Upcalls: 3 ( 3.6 %, 248.6 us/upcall)
Histograms
packets/it pkts/batch upcalls/it cycles/upcall
1 83 1 166 1 3 ...
15848 2
19952 2
...
50118 2
i.e. all the packets counted twice in 'pkts/batch' column and all the upcalls
counted twice in 'cycles/upcall' column.
CC: Jan Scheurich <[email protected]>
Fixes: 79f368756ce8 ("dpif-netdev: Detailed performance stats for PMDs")
Signed-off-by: Ilya Maximets <[email protected]>
---
lib/dpif-netdev-perf.c | 8 --------
1 file changed, 8 deletions(-)
diff --git a/lib/dpif-netdev-perf.c b/lib/dpif-netdev-perf.c index
8f0c9bc4f..52324858d 100644
--- a/lib/dpif-netdev-perf.c
+++ b/lib/dpif-netdev-perf.c
@@ -498,15 +498,7 @@ pmd_perf_end_iteration(struct pmd_perf_stats *s, int
rx_packets,
cycles_per_pkt = cycles / rx_packets;
histogram_add_sample(&s->cycles_per_pkt, cycles_per_pkt);
}
- if (s->current.batches > 0) {
- histogram_add_sample(&s->pkts_per_batch,
- rx_packets / s->current.batches);
- }
histogram_add_sample(&s->upcalls, s->current.upcalls);
- if (s->current.upcalls > 0) {
- histogram_add_sample(&s->cycles_per_upcall,
- s->current.upcall_cycles / s->current.upcalls);
- }
histogram_add_sample(&s->max_vhost_qfill, s->current.max_vhost_qfill);
/* Add iteration samples to millisecond stats. */
--
Thanks, applied to master and back to 2.10.
Ian
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