Re: 2.6.21 numa policy and huge pages not working

[dean gaudet <dean@arctic.org>]

On Tue, 15 May 2007, William Lee Irwin III wrote:

> On Tue, May 15, 2007 at 10:41:06PM -0700, dean gaudet wrote:
> > prior to 2.6.21 i could "numactl --interleave=all" and use SHM_HUGETLB and 
> > the interleave policy would be respected.  as of 2.6.21 it doesn't seem to 
> > respect the policy on SHM_HUGETLB request.
> > see test program below.
> > output from pre-2.6.21:
> > 2ab196200000 interleave=0-3 file=/2\040(deleted) huge dirty=32 N0=8 N1=8 N2=8 N3=8
> > 2ab19a200000 default file=/SYSV00000000\040(deleted) dirty=16384 active=0 N0=4096 N1=4096 N2=4096 N3=4096
> > output from 2.6.21:
> > 2b49b1c00000 default file=/10\040(deleted) huge dirty=32 N3=32
> > 2b49b5c00000 default file=/SYSV00000000\040(deleted) dirty=16384 active=0 N0=4096 N1=4096 N2=4096 N3=4096
> > was this an intentional behaviour change?  it seems to be only affecting 
> > SHM_HUGETLB allocations.  (i haven't tested hugetlbfs yet.)
> > run with "numactl --interleave=all ./shmtest"
> 
> This was not intentional. I'll search for where it broke.

ok i've narrowed it some... maybe.

in commit 8ef8286689c6b5bc76212437b85bdd2ba749ee44 things work fine, numa 
policy is respected...

the very next commit bc56bba8f31bd99f350a5ebfd43d50f411b620c7 breaks shm 
badly causing the test program to oops the kernel.

commit 516dffdcd8827a40532798602830dfcfc672294c fixes that breakage but 
numa policy is no longer respected.

i've added the authors of those two commits to the recipient list and 
reattached the test program.  hopefully someone can shed light on the 
problem.

-dean

#include <sys/mman.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>


static void *alloc_arena_shm(size_t arena_size, unsigned flags)
{
	FILE *fh;
	char buf[512];
	size_t huge_page_size;
	char *p;
	int shmid;
	void *arena;

	// find Hugepagesize in /proc/meminfo
	if ((fh = fopen("/proc/meminfo", "r")) == NULL) {
		perror("open(/proc/meminfo)");
		exit(1);
	}
	for (;;) {
		if (fgets(buf, sizeof(buf)-1, fh) == NULL) {
			fprintf(stderr, "didn't find Hugepagesize in /proc/meminfo");
			exit(1);
		}
		buf[sizeof(buf)-1] = '\0';
		if (strncmp(buf, "Hugepagesize:", 13) == 0) break;
	}
	p = strchr(buf, ':') + 1;
	huge_page_size = strtoul(p, 0, 0) * 1024;
	fclose(fh);

	// round the size up to multiple of huge_page_size
	arena_size = (arena_size + huge_page_size - 1) & ~(huge_page_size - 1);

	shmid = shmget(IPC_PRIVATE, arena_size, IPC_CREAT|IPC_EXCL|flags|0600);
	if (shmid == -1) {
		perror("shmget");
		exit(1);
	}

	arena = shmat(shmid, NULL, 0);
	if (arena == (void *)-1) {
		perror("shmat");
		exit(1);
	}

	if (shmctl(shmid, IPC_RMID, 0) == -1) {
		perror("shmctl warning");
	}

	return arena;
}

int main(int argc, char **argv)
{
        char buf[1024];
        const size_t sz = 64*1024*1024;
        void *arena = alloc_arena_shm(sz, SHM_HUGETLB);
        memset(arena, 0, sz);
        snprintf(buf, sizeof(buf), "grep ^%llx /proc/%d/numa_maps", (unsigned long long)arena, (int)getpid());
        system(buf);

        arena = alloc_arena_shm(sz, 0);
        memset(arena, 0, sz);
        snprintf(buf, sizeof(buf), "grep ^%llx /proc/%d/numa_maps", (unsigned long long)arena, (int)getpid());
        system(buf);

        return 0;
}