Tip Thread Specificity: AT-E
This event counts the number of times the memory order buffer (MOB) caused a load operation to be replayed. By default, this event is programmed to count those MOB replays caused by loads in which store-to-load forwarding was blocked. Note that this event counts replays, not instructions. Several replays may be generated by one instruction, and they may even be generated by bogus instructions, those that are speculatively executed after a mispredicted branch. Therefore, the related event MOB Load Replays Retired is much more commonly used and usually provides more useful information.
By default, the MOB Load Replays event counts replays caused by partial data or unaligned addresses only. You can configure it to count other replays as shown in the following table:
Event Mask Bits |
Description |
|---|---|
|
Bit 1: NO_STA |
Replayed because of unknown store address |
|
Bit 3: NO_STD |
Replayed because of unknown store data |
|
Bit 4: PARTIAL_DATA |
Replayed because of partially overlapped data access between the load and store operations |
|
Bit 5: UNALGN_ADDR |
Replayed because the lower 4 bits of the linear address do not match between the load and store operations |
Tip See MOB Load Replays Retired for more information on what causes MOB Load Replays and how to avoid them.
For more information, see the latest processor optimization reference manual.