On Mon, Nov 02, 2015 at 07:27:26PM -0800, Dan Williams wrote: > On Mon, Nov 2, 2015 at 4:51 PM, Dave Chinner <da...@fromorbit.com> wrote: > > On Sun, Nov 01, 2015 at 11:29:53PM -0500, Dan Williams wrote: > > The zeroing (and the data, for that matter) doesn't need to be > > committed to persistent store until the allocation is written and > > committed to the journal - that will happen with a REQ_FLUSH|REQ_FUA > > write, so it makes sense to deploy the big hammer and delay the > > blocking CPU cache flushes until the last possible moment in cases > > like this. > > In pmem terms that would be a non-temporal memset plus a delayed > wmb_pmem at REQ_FLUSH time. Better to write around the cache than > loop over the dirty-data issuing flushes after the fact. We'll bump > the priority of the non-temporal memset implementation.
Why is it better to do two synchronous physical writes to memory within a couple of microseconds of CPU time rather than writing them through the cache and, in most cases, only doing one physical write to memory in a separate context that expects to wait for a flush to complete? Cheers, Dave. -- Dave Chinner da...@fromorbit.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
