On Mon, Jun 1, 2015 at 1:58 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote: > > * Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > >> You answered the wrong question. :) I understand the point of the non-temporal >> stores -- I don't understand the point of using non-temporal stores to *WB >> memory*. I think we should be okay with having the kernel mapping use WT >> instead. > > WB memory is write-through, but they are still fully cached for reads. > > So non-temporal instructions influence how the CPU will allocate (or not allocate) > WT cache lines. > I'm doing a terrible job of saying what I mean. Given that we're using non-temporal writes, the kernel code should work correctly and with similar performance regardless of whether the mapping is WB or WT. It would still be correct, if slower, with WC or UC, and, if we used explicit streaming reads, even that would matter less. I think this means that we are free to switch the kernel mapping between WB and WT as needed to improve DAX behavior. We could even plausibly do it at runtime. --Andy > Thanks, > > Ingo -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>