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postcopy: enhance ram_block_discard_range for hugepages

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Unfortunately madvise DONTNEED doesn't work on hugepagetlb
so use fallocate(FALLOC_FL_PUNCH_HOLE)
qemu_fd_getpagesize only sets the page based off a file
if the file is from hugetlbfs.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20170224182844.32452-6-dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Dr. David Alan Gilbert 2017-02-24 18:28:33 +00:00
parent d3a5038c46
commit e2fa71f527
1 changed files with 20 additions and 4 deletions
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24
exec.c
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@ -46,6 +46,11 @@
#include "sysemu/xen-mapcache.h"
#include "trace-root.h"
#ifdef CONFIG_FALLOCATE_PUNCH_HOLE
#include <fcntl.h>
#include <linux/falloc.h>
#endif
#endif
#include "exec/cpu-all.h"
#include "qemu/rcu_queue.h"
@ -3326,12 +3331,23 @@ int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length)
errno = ENOTSUP; /* If we are missing MADVISE etc */
if (rb->page_size == qemu_host_page_size) {
#if defined(CONFIG_MADVISE)
/* Note: We need the madvise MADV_DONTNEED behaviour of definitely
* freeing the page.
*/
ret = madvise(host_startaddr, length, MADV_DONTNEED);
/* Note: We need the madvise MADV_DONTNEED behaviour of definitely
* freeing the page.
*/
ret = madvise(host_startaddr, length, MADV_DONTNEED);
#endif
} else {
/* Huge page case - unfortunately it can't do DONTNEED, but
* it can do the equivalent by FALLOC_FL_PUNCH_HOLE in the
* huge page file.
*/
#ifdef CONFIG_FALLOCATE_PUNCH_HOLE
ret = fallocate(rb->fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
start, length);
#endif
}
if (ret) {
ret = -errno;
error_report("ram_block_discard_range: Failed to discard range "