rt-tests: queuelat: Remove initial manpage, and replace
Remove the intial manpage and replace it with one written by the author of queuelat Signed-off-by: John Kacur <jkacur@redhat.com>
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John Kacur
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.\"
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.TH queuelat 8 "September 17, 2018"
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.SH NAME
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.B queuelat
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.SH SYNOPSIS
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.B queuelat
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.sh DESCRIPTION
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cyclictest does not catch all cases where packet forwarding
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latency can exceed a given threshold.
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Example:
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# taskset -c 3 ./queuelat -m 20000 -c 100 -p 13 -f `sh ./get_cpuinfo_mhz.sh`
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# rmmod targeted-ipi; insmod ./targeted-ipi.ko ipidest=3 nripis=200 interval=2 delay=10
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<...>-4566 [003] .....11 4474.559880: tracing_mark_write: memmove block queue_size=28 queue_dec=279 queue_inc=307 delta=23685 ns
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<...>-4566 [003] .....11 4474.559912: tracing_mark_write: memmove block queue_size=63 queue_dec=279 queue_inc=314 delta=24198 ns
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<...>-4566 [003] .....11 4474.559937: tracing_mark_write: memmove block queue_size=97 queue_dec=279 queue_inc=313 delta=24090 ns
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<...>-4566 [003] .....11 4474.559965: tracing_mark_write: memmove block queue_size=130 queue_dec=279 queue_inc=312 delta=24048 ns
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<...>-4566 [003] .....11 4474.559993: tracing_mark_write: memmove block queue_size=162 queue_dec=279 queue_inc=311 delta=23957 ns
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<...>-4566 [003] .....11 4474.560018: tracing_mark_write: memmove block queue_size=193 queue_dec=279 queue_inc=310 delta=23912 ns
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<...>-4566 [003] .....11 4474.560046: tracing_mark_write: memmove block queue_size=225 queue_dec=279 queue_inc=311 delta=23965 ns
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<...>-4566 [003] .....11 4474.560074: tracing_mark_write: memmove block queue_size=257 queue_dec=279 queue_inc=311 delta=23971 ns
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<...>-4566 [003] .....11 4474.560102: tracing_mark_write: memmove block queue_size=288 queue_dec=279 queue_inc=310 delta=23902 ns
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<...>-4566 [003] .....11 4474.560127: tracing_mark_write: memmove block queue_size=320 queue_dec=279 queue_inc=311 delta=23945 ns
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<...>-4566 [003] .....11 4474.560155: tracing_mark_write: memmove block queue_size=351 queue_dec=279 queue_inc=310 delta=23921 ns
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<...>-4566 [003] .....11 4474.560180: tracing_mark_write: memmove block queue_size=381 queue_dec=279 queue_inc=309 delta=23839 ns
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<...>-4566 [003] .....11 4474.560208: tracing_mark_write: memmove block queue_size=412 queue_dec=279 queue_inc=310 delta=23876 ns
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<...>-4566 [003] .....11 4474.560236: tracing_mark_write: memmove block queue_size=443 queue_dec=279 queue_inc=310 delta=23886 ns
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<...>-4566 [003] .....11 4474.560261: tracing_mark_write: memmove block queue_size=474 queue_dec=279 queue_inc=310 delta=23901 ns
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<...>-4566 [003] .....11 4474.560288: tracing_mark_write: memmove block queue_size=505 queue_dec=279 queue_inc=310 delta=23891 ns
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<...>-4566 [003] .....11 4474.560316: tracing_mark_write: memmove block queue_size=535 queue_dec=279 queue_inc=309 delta=23822 ns
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<...>-4566 [003] .....11 4474.560341: tracing_mark_write: memmove block queue_size=565 queue_dec=279 queue_inc=309 delta=23815 ns
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<...>-4566 [003] .....11 4474.560353: tracing_mark_write: queue length exceeded: queue_size=565 max_queue_len=559
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# taskset -c 3 cyclictest -m -n -q -p95 -D 60m -h60 -i 200
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# rmmod targeted-ipi; insmod ./targeted-ipi.ko ipidest=3 nripis=20000 interval=2 delay=10
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Cyclictest results:
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# Total: 000068099
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# Min Latencies: 00001
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# Avg Latencies: 00002
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# Max Latencies: 00008
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# Histogram Overflows: 00000
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----- queuelat basics:
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Queuelat simulates a DPDK queue. From queuelat.c:
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Program parameters:
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max_queue_len: maximum latency allowed, in nanoseconds (int).
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cycles_per_packet: number of cycles to process one packet (int).
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mpps(million-packet-per-sec): million packets per second (float).
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tsc_freq_mhz: TSC frequency in MHz, as measured by TSC PIT calibration
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(search for "Detected XXX MHz processor" in dmesg, and use the integer part).
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How it works
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============
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The program in essence does:
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b = rdtsc();
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memmove(dest, src, n);
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a = rdtsc();
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delay = convert_to_ns(a - b);
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queue_size += packets_queued_in(delay);
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queue_size -= packets_processed;
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if (queue_size > max_queue_len)
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FAIL();
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packets_processed is fixed, and is estimated as follows:
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n is determined first, so that the stats bucket with highest count
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takes max_latency/2.
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for max_latency/2, we calculate how many packets can be drained
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in that time (using cycles_per_packet).
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Queuelat output
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===============
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During calibration, queuelat outputs the following table:
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[9600 - 9699] = 0 packetfillrates=[67 - 67]
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[9700 - 9799] = 7907 packetfillrates=[67 - 68]
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[9800 - 9899] = 42085 packetfillrates=[68 - 69]
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[9900 - 9999] = 7 packetfillrates=[69 - 69]
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[10000 - 10099] = 1 packetfillrates=[70 - 70]
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| | | |
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| | | |
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| | | |_________ [min - max] number of
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| | | packets the queue will reach
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| | | with specified mpps in this
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| | | time (without draining)
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| | |
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| | |______________________________ number of hits for this
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| | bucket
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| |
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| |______________________________________ min amount of time (ns)
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| this bucket accepts
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|______________________________________________ max amount of time (ns)
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this bucket accepts
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On success, queuelat outputs a table similar to cyclictest:
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[7000 - 7099] = 0
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[7100 - 7199] = 2
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[7200 - 7299] = 2457
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[7300 - 7399] = 21058
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| | |
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| | |___________ Number of processing loops that hit this
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| | bucket.
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| |
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| |____________________ Maximum number of nanoseconds of this bucket.
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|___________________________ Minimum number of nanoseconds in this bucket.
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That is a processing loop will account into a bucket if its duration
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is
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min_number_ns_in_bucket < duration < max_number_ns_in_bucket
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Automatic determination of Mpps
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===============================
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There is a script called determine_maximum_mpps.sh, which should be edited
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to include the pinning and -RT priority configuration for your machine.
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PREAMBLE="taskset -c 2 chrt -f 1"
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MAXLAT="20000"
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CYCLES_PER_PACKET="300"
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This script will find the maximum mpps parameter which can sustain:
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1) 10 consecutive 30 second runs.
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2) 1 run of 10 minutes.
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Without violating the latency specified with $MAXLAT.
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.BR
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.SH AUTHOR
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queuelat was written by Marcello Tosatti <mtosatti at redhat.com>
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.SH SEE ALSO
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.BR determine_maximum_mpps.sh
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.BR get_cpuinfo_mhz.sh
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.PP
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This manual page was created by John Kacur <jkacur at redhat.com>
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