Re: Pentium SSE prefetcht0 instruction... How do you make it work

Bulent Abali (
Thu, 27 Sep 2001 16:09:43 -0400

>Intel's p3/4 prefetch instructions are hints only. They are only executed
>asynchronously, and depend heavily on the other load on the processor at
>the time. They are not required to prefetch, *and* they are not required
>to be executed when you think they should in the flow of the program. You
>can serialize them by using an MFENCE instruction, but they still aren't
>guaranteed to run.
>Check the p4 manuals. In fact, I'm not sure prefetch was implemented in
>p3. I could be wrong, check the manual.
PREFETCHx are in P3. I am aware that processor executes them optionally.
MFENCE may be a good idea. If load/store queues are full the processor
may just drop the prefetch instruction. I should try this.
Thanks for the suggestion. /bulent

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at