Thanks for fixing this, Ilya! It was correct at the time it was committed but very likely to break afterwards. I should have removed the loop from the start and change the way you propose.
Acked-by: Jan Scheurich <[email protected]> > -----Original Message----- > From: Ilya Maximets [mailto:[email protected]] > Sent: Friday, 11 August, 2017 15:01 > To: [email protected] > Cc: Heetae Ahn <[email protected]>; Antonio Fischetti > <[email protected]>; Darrell Ball <[email protected]>; Ilya > Maximets <[email protected]>; Jan Scheurich <[email protected]> > Subject: [PATCH] dpif-netdev: Fix per packet cycles statistics. > > DP_STAT_LOOKUP_HIT statistics used mistakenly for calculation > of total number of packets. This leads to completely wrong > per packet cycles statistics. > > For example: > > emc hits:0 > megaflow hits:253702308 > avg. subtable lookups per hit:1.50 > miss:0 > lost:0 > avg cycles per packet: 248.32 (157498766585/634255770) > > In this case 634255770 total_packets value used for avg > per packet calculation: > > total_packets = 'megaflow hits' + 'megaflow hits' * 1.5 > > The real value should be 524.38 (157498766585/253702308) > > Fix that by summing only stats that reflects match/not match. > It's decided to make direct summing of required values instead of > disabling some stats in a loop to make calculations more clear and > avoid similar issues in the future. > > CC: Jan Scheurich <[email protected]> > Fixes: 3453b4d62a98 ("dpif-netdev: dpcls per in_port with sorted subtables") > Signed-off-by: Ilya Maximets <[email protected]> > --- > lib/dpif-netdev.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c > index e2cd931..17e1666 100644 > --- a/lib/dpif-netdev.c > +++ b/lib/dpif-netdev.c > @@ -755,7 +755,7 @@ pmd_info_show_stats(struct ds *reply, > unsigned long long stats[DP_N_STATS], > uint64_t cycles[PMD_N_CYCLES]) > { > - unsigned long long total_packets = 0; > + unsigned long long total_packets; > uint64_t total_cycles = 0; > int i; > > @@ -771,13 +771,12 @@ pmd_info_show_stats(struct ds *reply, > } else { > stats[i] = 0; > } > - > - if (i != DP_STAT_LOST) { > - /* Lost packets are already included in DP_STAT_MISS */ > - total_packets += stats[i]; > - } > } > > + /* Sum of all the matched and not matched packets gives the total. */ > + total_packets = stats[DP_STAT_EXACT_HIT] + stats[DP_STAT_MASKED_HIT] > + + stats[DP_STAT_MISS]; > + > for (i = 0; i < PMD_N_CYCLES; i++) { > if (cycles[i] > pmd->cycles_zero[i]) { > cycles[i] -= pmd->cycles_zero[i]; > -- > 2.7.4 _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
