[LTP] [PATCH] madvise06: wait a bit after madvise() call

[Jan Stancek <jstancek@redhat.com>]

----- Original Message -----
> From: "Li Wang" <liwang@redhat.com>
> To: "Jan Stancek" <jstancek@redhat.com>
> Cc: "Chunyu Hu" <chuhu@redhat.com>, ltp@lists.linux.it
> Sent: Friday, 22 July, 2016 5:46:03 AM
> Subject: Re: [LTP] [PATCH] madvise06: wait a bit after madvise() call
> 
> On Thu, Jul 21, 2016 at 04:23:27PM +0200, Jan Stancek wrote:
> > 
> > I'm starting to run out of ideas how we can test this somewhat reliably.
> > 
> > Attached is approach v3, which sets up memory cgroup:
> > - memory.limit_in_bytes is 128M
> > - we allocate 512M
> > - as consequence ~384M should be swapped while system should still have
> >   plenty of free memory, which should be available for cache
> 
> Drop caches before testing is really good, we think the same!
> 
> And setting cgroup shorten the test time if there could guarantee
> cgroup OOM is off and swappiness is a little larger, that would
> be more reliable I think.

Agreed, we can do that.

> 
> One question is that you wrote function count_swapped_pages() but
> didn't using it, seems forgot to put somewhere?

I left it in, just in case I would use it in v4.

> 
> Anyway, V3 is strong enough expecially it combines the two method
> together.

> save this function by oneline:
> 
>  /* drop caches*/
>  SAFE_FILE_PRINTF("/proc/sys/vm/drop_caches", "1");

Good point.

> 
> > 
> > 	sysinfo(&sys_buf_start);
> > 	if (sys_buf_start.freeram < 2 * CHUNK_SZ)
> > 		tst_brk(TCONF, "System RAM is too small, skip test");
> > 	if (sys_buf_start.freeswap < 2 * CHUNK_SZ)
> > 		tst_brk(TCONF, "System swap is too small");
> > 
> > 	SAFE_MKDIR("memory", 0700);
> > 	SAFE_MOUNT("memory", "memory", "cgroup", 0, "memory");

I'm thinking if I should turn this into normal mount and TCONF if
there is no memory cgroup support in kernel.

> > 	if (access("memory/memory.limit_in_bytes", R_OK | W_OK))
> > 		tst_brk(TCONF, "cgroup memory.limit_in_bytes needed");
> > 
> > 	SAFE_MKDIR("memory/madvise06", 0700);
> > 	SAFE_FILE_PRINTF("memory/madvise06/memory.limit_in_bytes", "%ld\n",
> > 		PASS_THRESHOLD);
> 
> Turn off oom, enlarge swappiness
> 
>  SAFE_FILE_PRINTF("memory/madvise06/memory.oom_control", "0");
>  SAFE_FILE_PRINTF("memory/madvise06/memory.swappiness", "60");

I'll add that.

> 
> > 	SAFE_FILE_PRINTF("memory/madvise06/tasks", "%d\n", getpid());
> > }
> > 
> > static void cleanup(void)
> > {
> > 	FILE *f = fopen("memory/tasks", "w");
> > 
> > 	if (f) {
> > 		fprintf(f, "%d\n", getpid());
> > 		fclose(f);
> > 	}
> > 	rmdir("memory/madvise06");
> > 	umount("memory");
> > }
> > 
> > static long count_swapped_pages(void *ptr, long pg_count)
> 
> A compile Warnning:
> 
> madvise06.c:94:13: warning: ‘count_swapped_pages’ defined but not used
> [-Wunused-function]
> static long count_swapped_pages(void *ptr, long pg_count)

I'll drop it in a patch.

Regards,
Jan

> 
> 
> Regards,
> Li Wang
>