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Exit loop if we have been there too long

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Checking each 64 pages is a random magic number as good as any other.
We don't want to test too many times, but on the other hand,
qemu_get_clock_ns() is not so expensive either.  We want to be sure
that we spent less than 50ms (half of buffered_file timer), if we
spent more than 100ms, all the accounting got wrong.

Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Juan Quintela 2012-05-22 16:27:59 +02:00
parent 5b3c963887
commit 4508bd9ed8
1 changed files with 18 additions and 0 deletions
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18
arch_init.c
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@ -309,12 +309,15 @@ static void migration_end(void)
memory_global_dirty_log_stop();
}
#define MAX_WAIT 50 /* ms, half buffered_file limit */
int ram_save_live(QEMUFile *f, int stage, void *opaque)
{
ram_addr_t addr;
uint64_t bytes_transferred_last;
double bwidth = 0;
int ret;
int i;
if (stage < 0) {
migration_end();
@ -354,6 +357,7 @@ int ram_save_live(QEMUFile *f, int stage, void *opaque)
bytes_transferred_last = bytes_transferred;
bwidth = qemu_get_clock_ns(rt_clock);
i = 0;
while ((ret = qemu_file_rate_limit(f)) == 0) {
int bytes_sent;
@ -362,6 +366,20 @@ int ram_save_live(QEMUFile *f, int stage, void *opaque)
if (bytes_sent == 0) { /* no more blocks */
break;
}
/* we want to check in the 1st loop, just in case it was the 1st time
and we had to sync the dirty bitmap.
qemu_get_clock_ns() is a bit expensive, so we only check each some
iterations
*/
if ((i & 63) == 0) {
uint64_t t1 = (qemu_get_clock_ns(rt_clock) - bwidth) / 1000000;
if (t1 > MAX_WAIT) {
DPRINTF("big wait: " PRIu64 " milliseconds, %d iterations\n",
t1, i);
break;
}
}
i++;
}
if (ret < 0) {