[LTP] [PATCH v2] getrusage03: account for percpu RSS counter batching

[Cyril Hrubis]

Hi!
> diff --git a/testcases/kernel/syscalls/getrusage/getrusage03.c b/testcases/kernel/syscalls/getrusage/getrusage03.c
> index a2cdd6158..38a100576 100644
> --- a/testcases/kernel/syscalls/getrusage/getrusage03.c
> +++ b/testcases/kernel/syscalls/getrusage/getrusage03.c
> @@ -13,9 +13,13 @@
>   * this program.
>   */
>  
> +#define _GNU_SOURCE
>  #include <stdlib.h>
>  #include <stdio.h>
>  
> +#include "lapi/cpuset.h"
> +#include "tst_safe_stdio.h"
> +#include "tst_cpu.h"
>  #include "tst_test.h"
>  #include "getrusage03.h"
>  
> @@ -23,12 +27,99 @@
>  
>  static struct rusage ru;
>  static long maxrss_init;
> +static long lower_allowance;
>  
>  static const char *const resource[] = {
>  	TESTBIN,
>  	NULL,
>  };
>  
> +static long count_online_cpus(void)
> +{
> +	FILE *fp = SAFE_FOPEN("/proc/stat", "r");
> +	char line[BUFSIZ];
> +	long count = 0;
> +
> +	while (fgets(line, sizeof(line), fp)) {
> +		if (line[0] == 'c' && line[1] == 'p' && line[2] == 'u' &&
> +		    line[3] >= '0' && line[3] <= '9')
> +			count++;
> +	}
> +
> +	if (ferror(fp))
> +		tst_brk(TBROK | TERRNO, "fgets(/proc/stat)");
> +
> +	SAFE_FCLOSE(fp);
> +
> +	if (!count)
> +		tst_brk(TBROK, "No online CPUs found in /proc/stat");
> +
> +	return count;
> +}
> +
> +static void pin_to_cpu(void)
> +{
> +	long ncpus = tst_ncpus_max();
> +	size_t size = CPU_ALLOC_SIZE(ncpus);
> +	cpu_set_t *mask = CPU_ALLOC(ncpus);
> +	int cpu = -1;
> +
> +	if (!mask)
> +		tst_brk(TBROK | TERRNO, "CPU_ALLOC()");
> +
> +	CPU_ZERO_S(size, mask);
> +	if (sched_getaffinity(0, size, mask) < 0) {
> +		CPU_FREE(mask);
> +		tst_brk(TBROK | TERRNO, "sched_getaffinity()");
> +	}
> +
> +	for (long i = 0; i < ncpus; i++) {
> +		if (CPU_ISSET_S((int)i, size, mask)) {
> +			cpu = (int)i;
> +			break;
> +		}
> +	}
> +
> +	if (cpu < 0) {
> +		CPU_FREE(mask);
> +		tst_brk(TBROK, "sched_getaffinity() returned an empty CPU mask");
> +	}
> +
> +	CPU_ZERO_S(size, mask);
> +	CPU_SET_S(cpu, size, mask);
> +	if (sched_setaffinity(0, size, mask) < 0) {
> +		CPU_FREE(mask);
> +		tst_brk(TBROK | TERRNO, "sched_setaffinity()");
> +	}
> +
> +	CPU_FREE(mask);
> +}
> +
> +static void setup(void)
> +{
> +	long online_cpus = count_online_cpus();
> +	long batch = MAX(32L, online_cpus * 2);
> +	long page_size = SAFE_SYSCONF(_SC_PAGESIZE);
> +	long batch_kib = batch * page_size / 1024;
> +
> +	lower_allowance = MAX(20 * 1024L, batch_kib);
> +	if (lower_allowance >= 102400L)
> +		tst_brk(TCONF, "Per-CPU RSS allowance is too large: %li KiB",
> +			lower_allowance);

As long as we pin to a single CPU the whole batch accounting shouldn't
be needed.

FYI Jan send a similar patch that just pins the process to a single CPU:

https://patchwork.kernel.org/project/ltp/patch/a308e12198ce96305761a009858fa4a80c91f932.1788518850.git.jstancek@redhat.com/

As far as I can tell that should be enough to fix the test.

-- 
Cyril Hrubis
chrubis@suse.cz