On Wed, Oct 29, 2014 at 12:02 PM, Jeff Moyer <jmoyer@xxxxxxxxxx> wrote: > "Jason B. Akers" <jason.b.akers@xxxxxxxxx> writes: > >> From: Dan Williams <dan.j.williams@xxxxxxxxx> >> >> Steal one unused bit from the priority class and two bits from the >> priority data, to implement a 3 bit cache-advice field. Similar to the >> page cache advice from fadvise() these hints are meant to be consumed >> by hybrid drives. Solid State Hyrbid-Drives, as defined by the SATA-IO >> Specification, implement up to a 4-bit cache priority that can be >> specified along with a FPDMA command. > > ionice is about setting an I/O scheduling class for a *process*. So, > unless I've missed something, this does not seem like the right > interface for passing I/O hints. > > You mention fadvise hints, which sounds like a good fit (and madvise > would be equally interesting), but I don't see where you've wired them > up in this patch set. Did I miss it? It turns out we didn't need it. It's straightforward to add, but I think "80%" of the benefit can be had by just having a per-thread cache priority. It's more powerful to say "any page cache page this thread touches, or any direct i/o this thread does, goes down the stack at the given priority". -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
