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mem: unmap unneeded space

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When we ask to reserve virtual areas, we usually include
alignment in the mapping size, and that memory ends up
being wasted. Wasting a gigabyte of VA space while trying to
reserve one gigabyte is pretty expensive on 32-bit, so after
we're done mapping, unmap unneeded space.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
This commit is contained in:
Anatoly Burakov 2018-04-30 12:21:43 +01:00 committed by Thomas Monjalon
parent 91fe57ac00
commit 68c3603867
1 changed files with 25 additions and 1 deletions
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26
lib/librte_eal/common/eal_common_memory.c
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@ -121,8 +121,32 @@ eal_get_virtual_area(void *requested_addr, size_t *size,
RTE_LOG(DEBUG, EAL, "Virtual area found at %p (size = 0x%zx)\n",
aligned_addr, *size);
if (unmap)
if (unmap) {
munmap(mapped_addr, map_sz);
} else if (!no_align) {
void *map_end, *aligned_end;
size_t before_len, after_len;
/* when we reserve space with alignment, we add alignment to
* mapping size. On 32-bit, if 1GB alignment was requested, this
* would waste 1GB of address space, which is a luxury we cannot
* afford. so, if alignment was performed, check if any unneeded
* address space can be unmapped back.
*/
map_end = RTE_PTR_ADD(mapped_addr, (size_t)map_sz);
aligned_end = RTE_PTR_ADD(aligned_addr, *size);
/* unmap space before aligned mmap address */
before_len = RTE_PTR_DIFF(aligned_addr, mapped_addr);
if (before_len > 0)
munmap(mapped_addr, before_len);
/* unmap space after aligned end mmap address */
after_len = RTE_PTR_DIFF(map_end, aligned_end);
if (after_len > 0)
munmap(aligned_end, after_len);
}
baseaddr_offset += *size;