On Oct 8, 2012 6:33 PM, "Alexandre Ratchov" <a...@caoua.org> wrote: > > On Sat, Oct 06, 2012 at 10:38:34PM +0200, Gregor Best wrote: > > Hi Alexandre, > > > > > [...] > > > This change is unclear for me; AFAIU, it removes the mechanism > > > which makes processes wake up with a priority depending on what > > > they are blocked on. > > > [...] > > > > Where do you see that? The code I removed/changed simply calulated the queue from > > which to remove `p` and removed it from there (similar for insertion). That needed > > to be changed to modify the RB tree used as a new runqueue. > > > > > [...] > > > For instance processes waking up from poll(2) or audio read/write > > > won't be prioritized any longer. If so, this would hurt audio and > > > other interactive processes but would improve cpu-intesive > > > bloatware. > > > [...] > > > > They weren't prioritised with the old version of this code either. > > > > AFAIU, when a process waits for an event (with tsleep(9)), it > provides the priority of the event it's waiting for (eg an audio > interrupt). When the event occurs, the process is put in the > runnable queue calculated from the priority. This way, interactive > processes (i.e. waiting for external events) are prioritized during > the event processing. > > This mechanism ensures audio and midi are usable without having to > manually tweak priorities. Furthermore, priorities changed > depending on what the process is doing. > > The most notable exception to above "rule" is the poll(2) > implementation, which still ignores priorities; it may need to be > fixed one day, but this is not the most urgent problem hurting > interactive processes. > [A > -- Alexandre >
Ratchov is correct, when a process sleeps you specify the priority you should have when waking up. I think george was referring to the old version of his code. The 4.4 bsd scheduler relies heavily on these priority boosts, i still didnt have a look at George's code, but an equivalent mechanism is usually needed. On cfs scheduling for example the processes forces a new delta calculation and gets a fraction proportional to all other runnables processes.
