closefrom performance improvement by using dirfd

[gmachin]

Issue type Feature request.

Redhat 6 does not have the closefrom system call and using the closefrom in lib/misc.c
The maximum fd for many systems is > 8000 fd. Only a small percentage are open fd and need to closed. The closing of the fd causes significant performance loss if peap/mschapv2 and ntlm_auth is used will cause threads to hang and force children to be killed. Analysis indicated the system was spending to much time in the closefrom function. The fix was to utilize dirfd to only close open fd. Below is the modified closefrom code:

ifndef HAVE_CLOSEFROM

int closefrom(int lowfd)
{
int i;
int maxfd = 256;

ifdef HAVE_DIRFD

    struct dirent *dent;
    DIR *dirp;
    char *endp;
    long fd;

endif

ifdef _SC_OPEN_MAX

    maxfd = sysconf(_SC_OPEN_MAX);
    if (maxfd < 0) {
      maxfd = 256;
    }

endif

ifdef HAVE_DIRFD

    /* Use /proc/self/fd directory if it exists. */
    if ((dirp = opendir("/proc/self/fd")) != NULL) {
        while ((dent = readdir(dirp)) != NULL) {
            fd = strtol(dent->d_name, &endp, 10);
            if (dent->d_name != endp && *endp == '\0' &&
                fd >= 0 && fd < maxfd && fd >= lowfd && fd != dirfd(dirp))
                (void) close((int) fd);
        }
        (void) closedir(dirp);
        return(fd);
    }

endif /* HAVE_DIRFD */

    if (lowfd > maxfd) return 0;

    /*
     *      FIXME: return EINTR?
     *
     *      Use F_CLOSEM?
     */
    for (i = lowfd; i < maxfd; i++) {
      close(i);
    }
    return i;

}

endif

[alandekok]

Hmm.. that's depressing. closefrom() has been around for a LONG time.

I've pushed changes which might help. Does RH6 have F_MAXFD or F_CLOSEM?

i.e. do man fcntl, and look for those names.

[gmachin]

No I don’t see F_MAXFD or F_CLOSEM in the fcntl on RH6 or RH7.

I am running an older version of freeradius 2.2.5, but saw 2.2.9 used the same function, and wanted for you to know what I found.

Even changing maxfd to 1024 had significant impact, however using dirfd and closing only open fds > 3 had the best results.

I first tried closing all fd > 3 until I got a -1 and EBADF errno. That worked as well but that assumed all open fds were sequential and there were no gaps.

I saw other versions of closefrom using dirfd and that appeared to be a better solution.

Glenn

From: Alan DeKok notifications@github.com
Reply-To: FreeRADIUS/freeradius-server reply@reply.github.com
Date: Monday, September 26, 2016 at 6:13 AM
To: FreeRADIUS/freeradius-server freeradius-server@noreply.github.com
Cc: "gmachin@sandia.gov" GMachin@sandia.gov, Author author@noreply.github.com
Subject: [EXTERNAL] Re: [FreeRADIUS/freeradius-server] closefrom performance improvement by using dirfd (#1757)

Hmm.. that's depressing. closefrom() has bene around for a LONG time.

I've pushed changes which might help. Does RH6 have F_MAXFD or F_CLOSEM?

i.e. do man fcntl, and look for those names.

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[alandekok]

I've pushed a fix. Please verify, as we're trying to release 3.0.12 today or tomorrow.

[alandekok]

I've pushed fixes after some checks. They also improve closefrom() performance on OSX.