On Jan 10, 2008 12:13 AM, dean gaudet <[EMAIL PROTECTED]> wrote: > w.r.t. dan's cfq comments -- i really don't know the details, but does > this mean cfq will misattribute the IO to the wrong user/process? or is > it just a concern that CPU time will be spent on someone's IO? the latter > is fine to me... the former seems sucky because with today's multicore > systems CPU time seems cheap compared to IO. >
I do not see this affecting the time slicing feature of cfq, because as Neil says the work has to get done at some point. If I give up some of my slice working on someone else's I/O chances are the favor will be returned in kind since the code does not discriminate. The io-priority capability of cfq currently does not work as advertised with current MD since the priority is tied to the current thread and the thread that actually submits the i/o on a stripe is non-deterministic. So I do not see this change making the situation any worse. In fact, it may make it a bit better since there is a higher chance for the thread submitting i/o to MD to do its own i/o to the backing disks. Reviewed-by: Dan Williams <[EMAIL PROTECTED]> - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
