migration: do not overwrite zero pages

on incoming migration do not memset pages to zero if they already read as zero.
this will allocate a new zero page and consume memory unnecessarily. even
if we madvise a MADV_DONTNEED later this will only deallocate the memory
asynchronously.

Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Peter Lieven 2013-06-10 12:14:20 +02:00 committed by Juan Quintela
parent 9ef051e553
commit 211ea74022

View File

@ -835,6 +835,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
}
ch = qemu_get_byte(f);
if (ch != 0 || !is_zero_page(host)) {
memset(host, ch, TARGET_PAGE_SIZE);
#ifndef _WIN32
if (ch == 0 &&
@ -843,6 +844,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
qemu_madvise(host, TARGET_PAGE_SIZE, QEMU_MADV_DONTNEED);
}
#endif
}
} else if (flags & RAM_SAVE_FLAG_PAGE) {
void *host;