> > Switching topics slightly, prefetch extending the effective cache line > size was causing us some consternation, since we were never able to find > where it was documented. Do you have a reference to it? When did it start > happening? > > > It seems like it invalidates all software that was carefully written to > honor 64 byte cache lines. > > > IIRC Pentium 4 had 128 byte "sectors", but it was never fully explained > what these were, and the word died with the P4. >
I've seen adjacent cacheline prefetching on Intel processors since the Netburst days (well over a decade). Until Sandy bridge it was generally recommended to disable them because memory bandwidth often became an issue. These days it works on the L2 cache sitting along side a prefetcher that looks for patterns of cache line accesses. L1 has different prefetchers. It does have quite a noticeable effect on false sharing but not as much as when within the same 64 byte cache line. -- You received this message because you are subscribed to the Google Groups "mechanical-sympathy" group. To unsubscribe from this group and stop receiving emails from it, send an email to mechanical-sympathy+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
