Graeme Geldenhuys wrote: > pointed out). This sounds like an interesting topic and something > work understanding. After all, it gave me enough headaches and a > false positive - thinking it is a bug.
Btw, here is a quote from the interview, default length seems to be 150ms: (it also explains the usefulness of longer timeslices: caches) <quote> another property of SCHED_BATCH scheduling is the use of much longer timeslices. Eg. right now it's 3 seconds for a default priority SCHED_BATCH task - while normal tasks have 150 msec timeslices. For things like numeric calculations it's good to have as long timeslices as possible, to minimize the effect of cache trashing. Eg. on a sufficiently powerful CPU with a 2 MB L2 cache, the 'population time' of the cache can be as high as 10 milliseconds. So if there are two numeric calculation tasks that both fully utilize the L2 cache (in nonobvious patterns), and which context-switch every 150 milliseconds, then they will waste 10 milliseconds on cache-rebuilding in the first 6% of their timeslice. This shows up as a direct 6% slowdown of the numeric calculation jobs. Now, if SCHED_BATCH is used, and each task has a 3000 milliseconds timeslice, then the cache-rebuild overhead can be at most 0.3% - a far more acceptable number. </quote> Micha _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
