floatcomplex nerd sniped me into testing how many sigwinches i can get per second via terminal resizes

check.awk

1
/sent/ { stot += sent[s++] = $2 }
/recv/ { rtot += recv[r++] = $2 }
END {
    if (r != s)
        printf "error: s=%d r=%d\n", s, r
    for (i in sent)
        if (sent[i] < recv[i])
            printf "error: sent[%d]=%d recv[%d]=%d\n", i, sent[i], i, recv[i]
    printf "sent=%'d avg=%'d\n", stot, stot/s
    printf "recv=%'d avg=%'d\n", rtot, rtot/r
    printf "recv/sent=%.1f%%\n", 100*rtot/stot
}

pty.c

#define _GNU_SOURCE
#include <pty.h>
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/signalfd.h>
#include <sys/time.h>
#include <unistd.h>

void sched(int cpu, int policy, int priority) {
    cpu_set_t cpuset = {};
    CPU_SET(cpu, &cpuset);
    sched_setaffinity(0, sizeof cpuset, &cpuset);

    struct sched_param param = { .sched_priority = priority };
    sched_setscheduler(0, policy, &param);
}

int main() {
    int count = 0;
    char *map = mmap(0, 4096, 7, MAP_ANON|MAP_SHARED, -1, 0);

    sigset_t set = {};
    sigaddset(&set, SIGWINCH);
    sigaddset(&set, SIGALRM);
    sigprocmask(SIG_BLOCK, &set, 0);

    int sigfd = signalfd(-1, &set, SFD_NONBLOCK);
    int outfd = dup(1);

    int masterfd;
    struct winsize win = {};
    int pid = forkpty(&masterfd, 0, 0, &win);

    if (pid == 0) {
        sched(5, SCHED_RR, 10);

        struct itimerval it = { .it_value.tv_sec = 1 };
        setitimer(ITIMER_REAL, &it, 0);
        struct signalfd_siginfo si = {};
        while (1) {
            if (read(sigfd, &si, sizeof si) != sizeof si)
                continue;
            if (si.ssi_signo == SIGALRM)
                break;
            count++;
        }
    }
    else {
        sched(4, SCHED_RR, 10);

        while (!*map) {
            win.ws_col = win.ws_row = count++%100 + 10;
            ioctl(masterfd, TIOCSWINSZ, &win);
        }
    }
    *map = 1;
    dprintf(outfd, "%s: %d\n", pid==0 ? "recv" : "sent", count);
}

result

isabella@melon:~$ gcc -O3 pty.c && sudo nice -20 bash -c 'for i in {1..10}; do ./a.out; done' | awk -f check.awk 
sent: 3223005
recv: 3221137
recv: 3216769
sent: 3219834
sent: 3213705
recv: 3210557
recv: 3194343
sent: 3196125
recv: 3200260
sent: 3202761
recv: 3202258
sent: 3205005
sent: 3154642
recv: 3151621
recv: 3184421
sent: 3186805
sent: 3182962
recv: 3181104
recv: 3156765
sent: 3159112
sent=31,943,956 avg=3,194,395
recv=31,919,235 avg=3,191,923
recv/sent=99.9%



holy fuck cgroups are crazy expensive

isabella@melon:~$ sudo nice -20 bash -c 'echo $$ >> /sys/fs/cgroup/cgroup.procs; for i in {1..10}; do ./a.out; done' | awk -f check.awk
recv: 3618086
sent: 3619961
sent: 3588182
recv: 3586635
sent: 3547247
recv: 3543605
recv: 3566707
sent: 3568710
recv: 3574457
sent: 3576766
sent: 3564380
recv: 3559270
sent: 3537433
recv: 3534281
recv: 3531923
sent: 3534677
recv: 3531909
sent: 3533686
recv: 3522657
sent: 3524621
sent=35,595,663 avg=3,559,566
recv=35,569,530 avg=3,556,953
recv/sent=99.9%