void adjustOpenFilesLimit(void) {
    rlim_t maxfiles = server.maxclients+CONFIG_MIN_RESERVED_FDS;
    struct rlimit limit;

    if (getrlimit(RLIMIT_NOFILE,&limit) == -1) {
        serverLog(LL_WARNING,"Unable to obtain the current NOFILE limit (%s), assuming 1024 and setting the max clients configuration accordingly.",
            strerror(errno));
        server.maxclients = 1024-CONFIG_MIN_RESERVED_FDS;
    } else {
        rlim_t oldlimit = limit.rlim_cur;

        /* Set the max number of files if the current limit is not enough
         * for our needs. */
        if (oldlimit < maxfiles) {
            rlim_t bestlimit;
            int setrlimit_error = 0;

            /* Try to set the file limit to match 'maxfiles' or at least
             * to the higher value supported less than maxfiles. */
            bestlimit = maxfiles;
            while(bestlimit > oldlimit) {
                rlim_t decr_step = 16;

                limit.rlim_cur = bestlimit;
                limit.rlim_max = bestlimit;
                if (setrlimit(RLIMIT_NOFILE,&limit) != -1) break;
                setrlimit_error = errno;

                /* We failed to set file limit to 'bestlimit'. Try with a
                 * smaller limit decrementing by a few FDs per iteration. */
                if (bestlimit < decr_step) break;
                bestlimit -= decr_step;
            }

            /* Assume that the limit we get initially is still valid if
             * our last try was even lower. */
            if (bestlimit < oldlimit) bestlimit = oldlimit;

            if (bestlimit < maxfiles) {
                unsigned int old_maxclients = server.maxclients;
                server.maxclients = bestlimit-CONFIG_MIN_RESERVED_FDS;
                /* maxclients is unsigned so may overflow: in order
                 * to check if maxclients is now logically less than 1
                 * we test indirectly via bestlimit. */
                if (bestlimit <= CONFIG_MIN_RESERVED_FDS) {
                    serverLog(LL_WARNING,"Your current 'ulimit -n' "
                        "of %llu is not enough for the server to start. "
                        "Please increase your open file limit to at least "
                        "%llu. Exiting.",
                        (unsigned long long) oldlimit,
                        (unsigned long long) maxfiles);
                    exit(1);
                }
                serverLog(LL_WARNING,"You requested maxclients of %d "
                    "requiring at least %llu max file descriptors.",
                    old_maxclients,
                    (unsigned long long) maxfiles);
                serverLog(LL_WARNING,"Server can't set maximum open files "
                    "to %llu because of OS error: %s.",
                    (unsigned long long) maxfiles, strerror(setrlimit_error));
                serverLog(LL_WARNING,"Current maximum open files is %llu. "
                    "maxclients has been reduced to %d to compensate for "
                    "low ulimit. "
                    "If you need higher maxclients increase 'ulimit -n'.",
                    (unsigned long long) bestlimit, server.maxclients);
            } else {
                serverLog(LL_NOTICE,"Increased maximum number of open files "
                    "to %llu (it was originally set to %llu).",
                    (unsigned long long) maxfiles,
                    (unsigned long long) oldlimit);
            }
        }
    }
}