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memlock: Make malloc reserve more robust against glibc tricks.

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This commit is contained in:
Petr Rockai 2014-09-30 10:56:59 +02:00
parent 542b03ee00
commit cf37c04347
1 changed files with 44 additions and 4 deletions
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48
lib/mm/memlock.c
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@ -25,6 +25,7 @@
#include <sys/mman.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <malloc.h>
#ifndef DEVMAPPER_SUPPORT
@ -133,9 +134,11 @@ static void _touch_memory(void *mem, size_t size)
static void _allocate_memory(void)
{
#ifndef VALGRIND_POOL
/* With Valgrind don't waste time in with preallocating memory */
void *stack_mem, *temp_malloc_mem;
struct rlimit limit;
int i, area = 0, missing = _size_malloc_tmp, max_areas = 32, hblks;
char *areas[max_areas];
/* Check if we could preallocate requested stack */
if ((getrlimit (RLIMIT_STACK, &limit) == 0) &&
@ -144,13 +147,50 @@ static void _allocate_memory(void)
_touch_memory(stack_mem, _size_stack);
/* FIXME else warn user setting got ignored */
if ((temp_malloc_mem = malloc(_size_malloc_tmp)))
_touch_memory(temp_malloc_mem, _size_malloc_tmp);
/*
* When a brk() fails due to fragmented address space (which sometimes
* happens when we try to grab 8M or so), glibc will make a new
* arena. In this arena, the rules for using “direct” mmap are relaxed,
* circumventing the MAX_MMAPs and MMAP_THRESHOLD settings. We can,
* however, detect when this happens with mallinfo() and try to co-opt
* malloc into using MMAP as a MORECORE substitute instead of returning
* MMAP'd memory directly. Since MMAP-as-MORECORE does not munmap the
* memory on free(), this is good enough for our purposes.
*/
while (missing > 0) {
struct mallinfo inf = mallinfo();
hblks = inf.hblks;
if ((areas[area] = malloc(_size_malloc_tmp)))
_touch_memory(areas[area], _size_malloc_tmp);
inf = mallinfo();
if (hblks < inf.hblks) {
/* malloc cheated and used mmap, even though we told it
not to; we try with twice as many areas, each half
the size, to circumvent the faulty logic in glibc */
free(areas[area]);
_size_malloc_tmp /= 2;
} else {
++ area;
missing -= _size_malloc_tmp;
}
if (area == max_areas && missing > 0) {
/* Too bad. Warn the user and proceed, as things are
* most likely going to work out anyway. */
log_warn("WARNING: Failed to reserve memory, %d bytes missing.", missing);
break;
}
}
if ((_malloc_mem = malloc(_size_malloc)))
_touch_memory(_malloc_mem, _size_malloc);
free(temp_malloc_mem);
/* free up the reserves so subsequent malloc's can use that memory */
for (i = 0; i < area; ++i)
free(areas[i]);
#endif
}