static void bump_file_max_and_nr_open(void) {

        /* Let's bump fs.file-max and fs.nr_open to their respective maximums. On current kernels large
         * numbers of file descriptors are no longer a performance problem and their memory is properly
         * tracked by memcg, thus counting them and limiting them in another two layers of limits is
         * unnecessary and just complicates things. This function hence turns off 2 of the 4 levels of limits
         * on file descriptors, and makes RLIMIT_NOLIMIT (soft + hard) the only ones that really matter. */

#if BUMP_PROC_SYS_FS_FILE_MAX || BUMP_PROC_SYS_FS_NR_OPEN
        int r;
#endif

#if BUMP_PROC_SYS_FS_FILE_MAX
        /* The maximum the kernel allows for this since 5.2 is LONG_MAX, use that. (Previously things were
         * different, but the operation would fail silently.) */
        r = sysctl_write("fs/file-max", LONG_MAX_STR);
        if (r < 0)
                log_full_errno(ERRNO_IS_NEG_FS_WRITE_REFUSED(r) ? LOG_DEBUG : LOG_WARNING, r,
                               "Failed to bump fs.file-max, ignoring: %m");
#endif

Warm-up