Commit edaae611 authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Juan Quintela
Browse files

migration: yay, buffering is gone



Buffering was needed because blocking writes could take a long time
and starve other threads seeking to grab the big QEMU mutex.

Now that all writes (except within _complete callbacks) are done
outside the big QEMU mutex, we do not need buffering at all.
Reviewed-by: default avatarOrit Wasserman <owasserm@redhat.com>
Reviewed-by: default avatarJuan Quintela <quintela@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarJuan Quintela <quintela@redhat.com>
parent 9b095037
......@@ -34,9 +34,6 @@ struct MigrationState
int64_t bandwidth_limit;
size_t bytes_xfer;
size_t xfer_limit;
uint8_t *buffer;
size_t buffer_size;
size_t buffer_capacity;
QemuThread thread;
QEMUBH *cleanup_bh;
......
......@@ -514,73 +514,41 @@ int64_t migrate_xbzrle_cache_size(void)
/* migration thread support */
static void buffered_flush(MigrationState *s)
{
size_t offset = 0;
ssize_t ret = 0;
DPRINTF("flushing %zu byte(s) of data\n", s->buffer_size);
if (qemu_file_get_error(s->file)) {
s->buffer_size = 0;
return;
}
qemu_fflush(s->file);
while (s->bytes_xfer < s->xfer_limit && offset < s->buffer_size) {
size_t to_send = MIN(s->buffer_size - offset, s->xfer_limit - s->bytes_xfer);
ret = migrate_fd_put_buffer(s, s->buffer + offset, to_send);
if (ret <= 0) {
DPRINTF("error flushing data, %zd\n", ret);
break;
} else {
DPRINTF("flushed %zd byte(s)\n", ret);
offset += ret;
s->bytes_xfer += ret;
}
}
DPRINTF("flushed %zu of %zu byte(s)\n", offset, s->buffer_size);
memmove(s->buffer, s->buffer + offset, s->buffer_size - offset);
s->buffer_size -= offset;
if (ret < 0) {
qemu_file_set_error(s->file, ret);
}
}
static int buffered_put_buffer(void *opaque, const uint8_t *buf,
int64_t pos, int size)
{
MigrationState *s = opaque;
ssize_t error;
ssize_t ret;
size_t sent;
DPRINTF("putting %d bytes at %" PRId64 "\n", size, pos);
error = qemu_file_get_error(s->file);
if (error) {
DPRINTF("flush when error, bailing: %s\n", strerror(-error));
return error;
ret = qemu_file_get_error(s->file);
if (ret) {
DPRINTF("flush when error, bailing: %s\n", strerror(-ret));
return ret;
}
if (size <= 0) {
return size;
}
if (size > (s->buffer_capacity - s->buffer_size)) {
DPRINTF("increasing buffer capacity from %zu by %zu\n",
s->buffer_capacity, size + 1024);
s->buffer_capacity += size + 1024;
s->buffer = g_realloc(s->buffer, s->buffer_capacity);
sent = 0;
while (size) {
ret = migrate_fd_put_buffer(s, buf, size);
if (ret <= 0) {
DPRINTF("error flushing data, %zd\n", ret);
return ret;
} else {
DPRINTF("flushed %zd byte(s)\n", ret);
sent += ret;
buf += ret;
size -= ret;
s->bytes_xfer += ret;
}
}
memcpy(s->buffer + s->buffer_size, buf, size);
s->buffer_size += size;
return size;
return sent;
}
static int buffered_close(void *opaque)
......@@ -712,10 +680,9 @@ static void *buffered_file_thread(void *opaque)
g_usleep((initial_time + BUFFER_DELAY - current_time)*1000);
sleep_time += qemu_get_clock_ms(rt_clock) - current_time;
}
buffered_flush(s);
if (qemu_file_get_error(s->file)) {
migrate_finish_set_state(s, MIG_STATE_ERROR);
} else if (last_round && s->buffer_size == 0) {
} else if (last_round) {
migrate_finish_set_state(s, MIG_STATE_COMPLETED);
}
}
......@@ -735,7 +702,6 @@ static void *buffered_file_thread(void *opaque)
qemu_bh_schedule(s->cleanup_bh);
qemu_mutex_unlock_iothread();
g_free(s->buffer);
return NULL;
}
......@@ -754,9 +720,6 @@ void migrate_fd_connect(MigrationState *s)
trace_migrate_set_state(MIG_STATE_ACTIVE);
s->bytes_xfer = 0;
s->buffer = NULL;
s->buffer_size = 0;
s->buffer_capacity = 0;
/* This is a best 1st approximation. ns to ms */
s->expected_downtime = max_downtime/1000000;
......
......@@ -1724,6 +1724,7 @@ void qemu_savevm_state_complete(QEMUFile *f)
}
qemu_put_byte(f, QEMU_VM_EOF);
qemu_fflush(f);
}
uint64_t qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size)
......
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