Hi,
Bob Picco wrote: [Wed Oct 01 2014, 05:51:09PM EDT]
> Hi,
> David Miller wrote: [Wed Oct 01 2014, 04:44:55PM EDT]
> > From: David Miller <davem@xxxxxxxxxxxxx>
> > Date: Wed, 01 Oct 2014 16:42:01 -0400 (EDT)
> >
> > > From: Bob Picco <bpicco@xxxxxxxxxx>
> > > Date: Wed, 1 Oct 2014 10:29:00 -0400
> > >
> > >> [root@ca-qasparc24 ~]# Unable to handle kernel NULL pointer dereference
> > >> BUG: Bad page map in process cc1 pte:9800003fdd860690 pmd:183f3f4b6000
> > >> page:000600007fbb0c00 count:107055216 mapcount:-524287 mapping: (null) index:0xfff8000107659c00
> > >> page flags: 0x6c4b6e00004f56(error|referenced|dirty|active|owner_priv_1|arch_1|reserved|private|head)
> > >> page dumped because: bad pte
> > >
Okay I have two meetings today.
This is where we seem to go bad on T4-2. We go equally bad very quickly on
T5-8 with all patches applied and !THP.
T4-2 is configured for THP "madvise". At this commit:
59a35b1 sparc64: Use kernel page tables for vmemmap.
we seem to fall apart on T4-2 with the program below.
./thp4-loop -a 1024 8192
This all needs to be reverified.
thanx!
<<toy program>>
#define _GNU_SOURCE
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <sys/mman.h>
#ifndef MADV_HUGEPAGE
#define MADV_HUGEPAGE 14
#endif
#define HPAGE_SHIFT (22UL)
#define HPAGE_SIZE (1UL << HPAGE_SHIFT)
#define PAGE_SHIFT (13UL)
#define NR_PAGES_HPAGE (HPAGE_SIZE >> PAGE_SHIFT)
#define __round_mask(x, y) ((__typeof__(x))((y)-1))
#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)
/* Note failure assumes an exit(1).
*/
void *allocate_thps(size_t sz)
{
int rc;
void *addr;
size_t align = HPAGE_SIZE;
rc = posix_memalign(&addr, align, sz);
if (rc)
perror("posix_memalign"), exit(1);
rc = madvise(addr, sz, MADV_HUGEPAGE);
if (rc) {
static int warn_once;
if (warn_once)
goto out;
fprintf(stderr, "Couldn't madvise for MADV_HUGEPAGE.\n");
warn_once = 1;
}
out:
return addr;
}
/* Verify the array.
*/
static void verify_thp(void *addr, void *end, int pagesize, int cnt)
{
unsigned long pc;
void *p;
for (pc = 0, p = addr; p < end; p += pagesize, pc++) {
if (*(unsigned long *) p != 0xbeefUL + (pc << 32UL)) {
fprintf(stderr, "\n\tcnt = %d pc=0x%lx thp = 0x%lx "
" addr=0x%lx *addr=0x%lx\n",
cnt, pc, pc >> 9UL, p, *(unsigned long *) p);
pc = (pc + NR_PAGES_HPAGE) & ~(NR_PAGES_HPAGE - 1);
pc--;
p = addr + (pc << PAGE_SHIFT);
}
}
}
int main(int argc, char **argv)
{
void *addr, *end, *p;
size_t sz;
int pagesize = getpagesize();
int loop, cnt, nthp, rc;
int recycle = 1;
unsigned long pc;
int optind = 0;
if (argc == 4 && argv[1][1] == 'a')
optind = 1;
else if (argc != 3)
fprintf(stderr, "%s: -a iterations 4Mb-pages\n",
argv[0]), exit(1);
rc = sscanf(argv[optind + 1], "%d", &loop);
if (rc != 1)
fprintf(stderr, "%s: sscanf (%s) failed\n",
argv[0], argv[optind + 1]), exit(1);
rc = sscanf(argv[optind + 2], "%d", &nthp);
if (rc != 1)
fprintf(stderr, "%s: sscanf (%s) failed\n",
argv[0], argv[optind + 2]), exit(1);
if (optind)
recycle = 0;
sz = HPAGE_SIZE * nthp;
for (cnt = 0; cnt < loop; cnt++) {
addr = allocate_thps(sz);
end = addr + sz;
fprintf(stderr, "[0x%lx-0x%lx) ",
(unsigned long) addr, (unsigned long) end);
for (pc = 0, p = addr; p < end; p += pagesize, pc++)
*(unsigned long *) p = 0xbeefUL + (pc << 32UL);
verify_thp(addr, end, pagesize, cnt);
sleep(cnt % 5);
verify_thp(addr, end, pagesize, cnt);
if (recycle)
free(addr);
fprintf(stdout, ".\n");
fflush(stdout);
}
fprintf(stderr, "%s: Done! cnt = %d\n", argv[0], cnt);
return 0;
}
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