Lowest latency notification method between process under Linux
Using the same code provided by @Artyom, but in a more morden hardware.
CPU: i9-9900k, closing C/S/P-state and set scaling policy as performance which keeps cores running at the maximum frequency(~5GHz).
OS: Preempt-RT patched Linux with kernel5.0.21, providing better real-time performance.
CPU affinity: two processes apartly running in two isolated cores, which keep away from irrelevant processes and interrupts AMSP.
Results:
Semaphore (sem_wait/sem_post - kernel - futex):
sleep us mean minimum median %99
1 1.75 ±0.1 1.60 1.74 1.82
10 1.76 ±0.0 1.61 1.75 1.83
100 2.12 ±0.3 1.59 2.24 2.42
1000 2.46 ±0.3 1.75 2.47 2.56
10000 2.45 ±0.1 2.11 2.44 2.54
Signal (kill/sigwait)
sleep us mean minimum median %99
1 2.15 ±0.2 2.00 2.13 2.22
10 2.12 ±0.2 1.93 2.11 2.19
100 2.56 ±0.3 2.00 2.67 2.88
1000 2.90 ±0.3 2.17 2.90 3.01
10000 2.94 ±0.5 2.66 2.89 3.03
Pipe (pipe + write/read)
sleep us mean minimum median %99
1 2.05 ±0.2 1.88 2.03 2.15
10 2.06 ±0.3 1.89 2.04 2.17
100 2.54 ±0.4 1.88 2.63 2.87
1000 2.98 ±0.3 2.27 2.98 3.09
10000 2.98 ±0.3 2.69 2.96 3.07
Socket (socketpair +write/read)
sleep us mean minimum median %99
1 3.11 ±0.4 2.85 3.09 3.22
10 3.14 ±0.1 2.92 3.14 3.25
100 3.66 ±0.5 2.92 3.74 4.01
1000 4.03 ±0.4 3.28 4.03 4.17
10000 3.99 ±0.4 3.64 3.96 4.10
As a reference busy waiting:
sleep us mean minimum median %99
1 0.07 ±0.1 0.06 0.07 0.07
10 0.07 ±0.1 0.06 0.07 0.07
100 0.07 ±0.0 0.06 0.07 0.08
1000 0.09 ±0.1 0.07 0.08 0.09
10000 0.09 ±0.1 0.07 0.09 0.09
Generally... There is almost no difference between the OS methods.
Setup:
- Two processes with affinity to two different CPUs.
- One process sleeps (nanosleep) for N microseconds measures current time and then notifies other process.
- Other process wakes measures current time and compares it to the client's time.
- Average, standard deviation, median and percentile 95 is calculated over 1K samples after warm-up on 100 notifications.
- OS: Linux 2.6.35 x86_64
- CPU: Intel i5 M460
Results:
Semaphore (sem_wait/sem_post - kernel - futex):
sleep us mean median %95
1 4.98 ±18.7 3.78 5.04
10 4.14 ±14.8 3.54 4.00
100 20.60 ±29.4 22.96 26.96
1000 49.42 ±37.6 30.62 78.75
10000 63.20 ±22.0 68.38 84.38
Signal (kill/sigwait)
sleep us mean median %95
1 4.69 ±3.8 4.21 5.39
10 5.91 ±14.8 4.19 7.45
100 23.90 ±17.7 23.41 35.90
1000 47.38 ±28.0 35.27 81.16
10000 60.80 ±19.9 68.50 82.36
Pipe (pipe + write/read)
sleep us mean median %95
1 3.75 ±5.9 3.46 4.45
10 4.42 ±3.5 3.84 5.18
100 23.32 ±25.6 24.17 38.05
1000 51.17 ±35.3 46.34 74.75
10000 64.69 ±31.0 67.95 86.80
Socket (socketpair +write/read)
sleep us mean median %95
1 6.07 ±3.2 5.55 6.78
10 7.00 ±7.1 5.51 8.50
100 27.57 ±14.1 28.39 50.86
1000 56.75 ±25.7 50.82 88.74
10000 73.89 ±16.8 77.54 88.46
As a reference busy waiting:
sleep us mean median %95
1 0.17 ±0.5 0.13 0.23
10 0.15 ±0.3 0.13 0.19
100 0.17 ±0.3 0.16 0.21
1000 0.22 ±0.1 0.18 0.35
10000 0.38 ±0.3 0.30 0.78