Re: [LTP] [PATCH V2 2/2] msgctl11: process message queues by portions

[chrubis@suse.cz]

Hi!
> As /proc/sys/kernel/msgmni value scales with an amount of host memory,
> on systems with several tens gigabytes of ram this testcase fails
> with "Not enough free pids" error.
> 
> Now if the amount of free pids is not enough to use all the queues at once
> we process the queues by portions (with the size based on an amount of free pids).
> 
> Signed-off-by: Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>
> ---
>  testcases/kernel/syscalls/ipc/msgctl/msgctl11.c |   71 ++++++++++++++++-------
>  1 files changed, 50 insertions(+), 21 deletions(-)
> 
> diff --git a/testcases/kernel/syscalls/ipc/msgctl/msgctl11.c b/testcases/kernel/syscalls/ipc/msgctl/msgctl11.c
> index 63ff88f..9ef18da 100644
> --- a/testcases/kernel/syscalls/ipc/msgctl/msgctl11.c
> +++ b/testcases/kernel/syscalls/ipc/msgctl/msgctl11.c
> @@ -60,6 +60,7 @@ static int rkidarray[MAXNKIDS];
>  static int wkidarray[MAXNKIDS];
>  static int tid;
>  static int nprocs, nreps, nkids, MSGMNI;
> +static int maxnprocs;
>  static int procstat;
>  
>  void setup(void);
> @@ -67,6 +68,7 @@ void cleanup(void);
>  
>  static void term(int);
>  static int dotest(key_t, int);
> +static void dotest_iteration(int off);
>  static void cleanup_msgqueue(int i, int tid);
>  
>  #ifdef UCLINUX
> @@ -84,8 +86,7 @@ static void do_child_3_uclinux(void);
>  
>  int main(int argc, char **argv)
>  {
> -	int i, j, ok, pid;
> -	int count, status;
> +	int i, j, ok;
>  
>  #ifdef UCLINUX
>  	char *msg;
> @@ -109,7 +110,6 @@ int main(int argc, char **argv)
>  	if (argc == 1) {
>  		/* Set default parameters */
>  		nreps = MAXNREPS;
> -		nprocs = MSGMNI;
>  		nkids = maxnkids;
>  	} else if (argc == 4) {
>  		if (atoi(argv[1]) > MAXNREPS) {
> @@ -120,13 +120,12 @@ int main(int argc, char **argv)
>  		} else {
>  			nreps = atoi(argv[1]);
>  		}
> -		if (atoi(argv[2]) > MSGMNI) {
> +		if (atoi(argv[2]) > maxnprocs) {
>  			tst_resm(TCONF,
>  				 "Requested number of processes too large, setting to Max. of %d",

                                 This should be TINFO

> -				 MSGMNI);
> -			nprocs = MSGMNI;
> +				 maxnprocs);
>  		} else {
> -			nprocs = atoi(argv[2]);
> +			maxnprocs = atoi(argv[2]);
>  		}
>  		if (atoi(argv[3]) > maxnkids) {
>  			tst_resm(TCONF,
> @@ -153,7 +152,7 @@ int main(int argc, char **argv)
>  	/* Set up array of unique keys for use in allocating message
>  	 * queues
>  	 */
> -	for (i = 0; i < nprocs; i++) {
> +	for (i = 0; i < MSGMNI; i++) {
>  		ok = 1;
>  		do {
>  			/* Get random key */
> @@ -172,13 +171,45 @@ int main(int argc, char **argv)
>  			}
>  		} while (ok == 0);
>  	}
> -	/* Fork a number of processes (nprocs), each of which will
> +	/* Fork a number of processes, each of which will
>  	 * create a message queue with several (nkids) reader/writer
>  	 * pairs which will read and write a number (iterations)
>  	 * of random length messages with specific values (keys).
> +	 *
> +	 * We do not fork more than maxnprocs at a time and
> +	 * we fork until all the message queues get used.
>  	 */
>  
> +	if (MSGMNI <= maxnprocs) {
> +		nprocs = MSGMNI;
> +		dotest_iteration(0);
> +	} else {
> +		for (i = 0; i < (MSGMNI / maxnprocs); i++) {
> +			nprocs = maxnprocs;
> +			dotest_iteration(i*(MSGMNI / maxnprocs));
> +		}
> +
> +		nprocs = MSGMNI % maxnprocs;
> +		dotest_iteration(i*(MSGMNI / maxnprocs));
> +	}
> +
> +	tst_resm(TPASS, "msgctl11 ran successfully!");
> +
> +	cleanup();
> +	tst_exit();
> +}
> +
> +static void dotest_iteration(int off)
> +{
> +	key_t key;
> +	int i, count, status;
> +	pid_t pid;
> +
> +	memset(pidarray, 0, sizeof(pidarray));
> +
>  	for (i = 0; i < nprocs; i++) {
> +		key = keyarray[off + i];
> +
>  		if ((pid = FORK_OR_VFORK()) < 0)
>  			tst_brkm(TFAIL, cleanup,
>  				 "Fork failed (may be OK if under stress)");
> @@ -186,13 +217,13 @@ int main(int argc, char **argv)
>  		/* Child does this */
>  		if (pid == 0) {
>  #ifdef UCLINUX
> -			if (self_exec(argv[0], "ndd", 1, keyarray[i], i) < 0) {
> +			if (self_exec(argv0, "ndd", 1, key, i) < 0) {
>  				printf("\tself_exec failed\n");
>  				exit(FAIL);
>  			}
>  #else
>  			procstat = 1;
> -			exit(dotest(keyarray[i], i));
> +			exit(dotest(key, i));
>  #endif
>  		}
>  		pidarray[i] = pid;
> @@ -219,11 +250,6 @@ int main(int argc, char **argv)
>  		tst_brkm(TFAIL, cleanup,
>  			 "Wrong number of children exited, Saw %d, Expected %d",
>  			 count, nprocs);
> -
> -	tst_resm(TPASS, "msgctl11 ran successfully!");
> -
> -	cleanup();
> -	tst_exit();
>  }
>  
>  #ifdef UCLINUX
> @@ -447,6 +473,8 @@ void setup(void)
>  		tst_brkm(TBROK, cleanup,
>  			 "Max number of message queues already used, cannot create more.");
>  
> +	tst_resm(TINFO, "Found %d available message queues", MSGMNI);
> +
>  	free_pids = get_free_pids();
>  	if (free_pids < 0) {
>  		tst_brkm(TBROK, cleanup, "Can't obtain free_pid count");
> @@ -454,11 +482,12 @@ void setup(void)
>  		tst_brkm(TBROK, cleanup, "No free pids");
>  	}
>  
> -	if ((MSGMNI * MAXNKIDS * 2) > (free_pids / 2)) {
> -		maxnkids = ((free_pids / 4) / MSGMNI);
> -		if (!maxnkids)
> -			tst_brkm(TBROK, cleanup, "Not enough free pids");
> -	}

Removing this part of the code makes the test run more than ten times
longer because now the maximal number of reader/writer pairs is set to
default value (10) and not to 1 which is what the code did previously. I
guess that this was intentional but it took me some time to figure that
out.

Now what I would like to do is to set maxkids default to 1 to preserve
the test behavior without any parameters and we can eventually add a few
more runtest entires with more interesting options too.

> +	/* We don't use more than a half of available pids.
> +	 * For each child we fork up to 2*maxnkids grandchildren. */
> +	maxnprocs = (free_pids / 2) / (1 + 2 * maxnkids);
> +
> +	if (!maxnprocs)
> +		tst_brkm(TBROK, cleanup, "Not enough free pids");
>  
>  	tst_resm(TINFO, "Using upto %d pids", free_pids / 2);
>  }

-- 
Cyril Hrubis
chrubis@suse.cz

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