For the TCP throughput tests, we use iperf3's -O "omit" option which
ignores results for the given time at the beginning of the test. Currently
we calculate this as 1/6th of the test measurement time. The purpose of
-O, however, is to skip over the TCP slow start period, which in no way
depends on the overall length of the test.
The slow start time is roughly speaking
log_2 ( max_window_size / MSS ) * round_trip_time
These factors all vary between tests and machines we're running on, but we
can estimate some reasonable bounds for them:
* The maximum window size is bounded by the buffer sizes at each end,
which shouldn't exceed 16MiB
* The mss varies with the MTU we use, but the smallest we use in tests is
~256 bytes
* Round trip time will vary with the system, but with these essentially
local transfers it will typically be well under 1ms (on my laptop it is
closer to 0.03ms)
That gives a worst case slow start time of about 16ms. Setting an omit
time of 0.1s uniformly is therefore more than enough, and substantially
smaller than what we calculate now for the default case (10s / 6 ~= 1.7s).
This reduces total time for the standard benchmark run by around 30s.
Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
test/perf/passt_tcp | 2 +-
test/perf/pasta_tcp | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/test/perf/passt_tcp b/test/perf/passt_tcp
index da4e369..631a407 100644
--- a/test/perf/passt_tcp
+++ b/test/perf/passt_tcp
@@ -40,7 +40,7 @@ hout FREQ [ -n "__FREQ_CPUFREQ__" ] && echo
__FREQ_CPUFREQ__ || echo __FREQ_PROC
set THREADS 1
set STREAMS 8
set TIME 10
-hout OMIT echo __TIME__ / 6 | bc -l
+set OMIT 0.1
set OPTS -Z -P __STREAMS__ -l 1M -O__OMIT__
info Throughput in Gbps, latency in µs, one thread at __FREQ__ GHz, __STREAMS__ streams
diff --git a/test/perf/pasta_tcp b/test/perf/pasta_tcp
index 11c73f8..7777532 100644
--- a/test/perf/pasta_tcp
+++ b/test/perf/pasta_tcp
@@ -24,7 +24,7 @@ ns /sbin/sysctl -w net.ipv4.tcp_timestamps=0
set THREADS 2
set STREAMS 2
set TIME 10
-hout OMIT echo __TIME__ / 6 | bc -l
+set OMIT 0.1
set OPTS -Z -w 4M -l 1M -P __STREAMS__ -O__OMIT__
hout FREQ_PROCFS (echo "scale=1"; sed -n 's/cpu MHz.*:
\([0-9]*\)\..*$/(\1+10^2\/2)\/10^3/p' /proc/cpuinfo) | bc -l | head -n1
--
2.41.0