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Dave noticed that unprivileged process can allocate significant amount of
memory -- >500 MiB on x86_64 -- and stay unnoticed by oom-killer and
memory cgroup. The trick is to allocate a lot of PMD page tables. Linux
kernel doesn't account PMD tables to the process, only PTE.
The use-cases below use few tricks to allocate a lot of PMD page tables
while keeping VmRSS and VmPTE low. oom_score for the process will be 0.
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#define PUD_SIZE (1UL << 30)
#define PMD_SIZE (1UL << 21)
#define NR_PUD 130000
int main(void)
{
char *addr = NULL;
unsigned long i;
prctl(PR_SET_THP_DISABLE);
for (i = 0; i < NR_PUD ; i++) {
addr = mmap(addr + PUD_SIZE, PUD_SIZE, PROT_WRITE|PROT_READ,
MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
if (addr == MAP_FAILED) {
perror("mmap");
break;
}
*addr = 'x';
munmap(addr, PMD_SIZE);
mmap(addr, PMD_SIZE, PROT_WRITE|PROT_READ,
MAP_ANONYMOUS|MAP_PRIVATE|MAP_FIXED, -1, 0);
if (addr == MAP_FAILED)
perror("re-mmap"), exit(1);
}
printf("PID %d consumed %lu KiB in PMD page tables\n",
getpid(), i * 4096 >> 10);
return pause();
}
The patch addresses the issue by account PMD tables to the process the
same way we account PTE.
The main place where PMD tables is accounted is __pmd_alloc() and
free_pmd_range(). But there're few corner cases:
- HugeTLB can share PMD page tables. The patch handles by accounting
the table to all processes who share it.
- x86 PAE pre-allocates few PMD tables on fork.
- Architectures with FIRST_USER_ADDRESS > 0. We need to adjust sanity
check on exit(2).
Accounting only happens on configuration where PMD page table's level is
present (PMD is not folded). As with nr_ptes we use per-mm counter. The
counter value is used to calculate baseline for badness score by
oom-killer.
Signed-off-by: Kirill A. Shutemov <[email protected]>
Reported-by: Dave Hansen <[email protected]>
Cc: Hugh Dickins <[email protected]>
Reviewed-by: Cyrill Gorcunov <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: David Rientjes <[email protected]>
Tested-by: Sedat Dilek <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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One bit in ->vm_flags is unused now!
Signed-off-by: Kirill A. Shutemov <[email protected]>
Cc: Dan Carpenter <[email protected]>
Cc: Michal Hocko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Now that the external page_cgroup data structure and its lookup is
gone, let the generic bad_page() check for page->mem_cgroup sanity.
Signed-off-by: Johannes Weiner <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Vladimir Davydov <[email protected]>
Acked-by: David S. Miller <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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- s/KERN_ALERT/pr_emerg/: we're going BUG so let's maximize the changes
of getting the message out.
- convert debug.c to pr_foo()
Cc: Sasha Levin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Very similar to VM_BUG_ON_PAGE and VM_BUG_ON_VMA, dump struct_mm when the
bug is hit.
[[email protected]: coding-style fixes]
[[email protected]: fix build]
[[email protected]: fix build some more]
[[email protected]: do strange things to avoid doing strange things for the comma separators]
Signed-off-by: Sasha Levin <[email protected]>
Cc: Dave Jones <[email protected]>
Signed-off-by: Michal Hocko <[email protected]>
Cc: Valdis Kletnieks <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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dump_page() and dump_vma() are not specific to page_alloc.c, move them out
so page_alloc.c won't turn into the unofficial debug repository.
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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