On Tue, Dec 15, 2015 at 9:53 AM, Luck, Tony <tony.luck@xxxxxxxxx> wrote: >>> ... and the non-temporal version is the optimal one even though we're >>> defaulting to copy_user_enhanced_fast_string for memcpy on modern Intel >>> CPUs...? > > My current generation cpu has a bit of an issue with recovering from a > machine check in a "rep mov" ... so I'm working with a version of memcpy > that unrolls into individual mov instructions for now. > >> At least the pmem driver use case does not want caching of the >> source-buffer since that is the raw "disk" media. I.e. in >> pmem_do_bvec() we'd use this to implement memcpy_from_pmem(). >> However, caching the destination-buffer may prove beneficial since >> that data is likely to be consumed immediately by the thread that >> submitted the i/o. > > I can drop the "nti" from the destination moves. Does "nti" work > on the load from source address side to avoid cache allocation? My mistake, I don't think we have an uncached load capability, only store. > On another topic raised by Boris ... is there some CONFIG_PMEM* > that I should use as a dependency to enable all this? I'd rather make this a "select ARCH_MCSAFE_MEMCPY". Since it's not a hard dependency and the details will be hidden behind memcpy_from_pmem(). Specifically, the details will be handled by a new arch_memcpy_from_pmem() in arch/x86/include/asm/pmem.h to supplement the existing arch_memcpy_to_pmem(). -- 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>