On Wed, Apr 18, 2007 at 03:59:06PM -0400, Steffen Persvold wrote: > I'm just curious what is believed to be "small messages" in this context > today ?
Oh, in this case I was meaning "up to 64 kbytes". Our current break point between PIO and DMA is 64000 bytes. > Back then we were struggling with PIO transfers and how they were > treated in the CPU/North bridge (write combining and all that). I > believe this might still be an issue, correct ? Yes and no. We haven't run into any hardware issues with modern hardware; there have been some quirks, but we have overcome them. >From the software point of view, manipulating MTRRs has proven to be problemmatic with a few BIOSes that don't have a "discrete mtrr" option. Apparently these days few or no graphics cards currently use write combining, so it's only a few network cards that do. In most cases we can manipulate the mtrrs after boot to fix this. Getting formal support for PAT in the Linux kernel is the long-term fix for this. -- greg _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
