/*
* unfortunately, many of the places that currently set a lock to blocking
- * don't end up blocking for every long, and often they don't block
- * at all. For a dbench 50 run, if we don't spin one the blocking bit
+ * don't end up blocking for very long, and often they don't block
+ * at all. For a dbench 50 run, if we don't spin on the blocking bit
* at all, the context switch rate can jump up to 400,000/sec or more.
*
* So, we're still stuck with this crummy spin on the blocking bit,
static int btrfs_spin_on_block(struct extent_buffer *eb)
{
int i;
+
for (i = 0; i < 512; i++) {
- cpu_relax();
if (!test_bit(EXTENT_BUFFER_BLOCKING, &eb->bflags))
return 1;
if (need_resched())
break;
+ cpu_relax();
}
return 0;
}
{
int i;
- spin_nested(eb);
- if (!test_bit(EXTENT_BUFFER_BLOCKING, &eb->bflags))
- return 1;
- spin_unlock(&eb->lock);
-
+ if (btrfs_spin_on_block(eb)) {
+ spin_nested(eb);
+ if (!test_bit(EXTENT_BUFFER_BLOCKING, &eb->bflags))
+ return 1;
+ spin_unlock(&eb->lock);
+ }
/* spin for a bit on the BLOCKING flag */
for (i = 0; i < 2; i++) {
+ cpu_relax();
if (!btrfs_spin_on_block(eb))
break;
DEFINE_WAIT(wait);
wait.func = btrfs_wake_function;
+ if (!btrfs_spin_on_block(eb))
+ goto sleep;
+
while(1) {
spin_nested(eb);
* spin for a bit, and if the blocking flag goes away,
* loop around
*/
+ cpu_relax();
if (btrfs_spin_on_block(eb))
continue;
-
+sleep:
prepare_to_wait_exclusive(&eb->lock_wq, &wait,
TASK_UNINTERRUPTIBLE);