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authorDavid Gibson <david@gibson.dropbear.id.au>2023-11-06 18:08:33 +1100
committerStefano Brivio <sbrivio@redhat.com>2023-11-07 09:56:24 +0100
commit53ff387156380bee9acb5fe2ca62af97b9ccce36 (patch)
treeb448f18823b5ee00f81d396db60a66d607d32508 /test/perf/passt_tcp
parentaa0bb9f471627c10b3c71fc9dacd06c642d88ad6 (diff)
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test/perf: Simplify calculation of "omit" time for TCP throughput
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@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Diffstat (limited to 'test/perf/passt_tcp')
-rw-r--r--test/perf/passt_tcp2
1 files changed, 1 insertions, 1 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