On Thu, May 21, 2009 at 3:59 AM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > On Wed, 20 May 2009, GeunSik Lim wrote: > >> 2009/5/20 GeunSik Lim <leemgs1@xxxxxxxxx>: >> > >> > >> > Dear Ingo, >> > >> > >> > I made 2 patch files again about static prioriy levels according to ingo's advice >> > and explanation. (Reference: http://marc.info/?t=124211992800003&r=1&w=2 archives. ) >> > >> > Fix static priority related range and chart map(userspace/kernelspace) of ftrace. >> > - about chart map of static priority in ftrace.txt file >> > - about static priority levels(range) in sched-rt-group.txt file >> > >> > >> > commit d6af702008117ca489a2f5476239d1688a517e98 >> > Author: GeunSik,Lim <leemgs1@xxxxxxxxx> >> > Date: Tue May 12 17:20:32 2009 +0900 >> > >> > sched: fix typo in sched-rt-group.txt file >> > >> > Fix typo about static priority's range. >> > >> > * Kernel Space priority 0(high) to 99(low) --> User Space RT priority 99(high) to 1(low) >> > * Kernel Space priority 100(high) to 139(low)--> User Space nice -20(high) to 19(low) >> > >> >> Ingo, >> I want to change some descriptions according to below discussion. >> >> before) * Kernel Space priority 0(high) to 99(low) --> User Space RT >> priority 99(high) to 1(low) >> after) * Kernel Space priority 0(high) to 98(low) --> User Space >> RT priority 99(high) to 1(low) >> >> I want to your advice and opinion about this changes. >> >> If I mistook, Please correct me. >> >> thks. >> >> >> >> Steven Rostedt: >> Shouldn't that be: >> Kernel priority: 0(high) to 98(low) ==> user RT priority 99(high) to 1(low) >> >> GeunSik Lim : >> Thank you for your opinion. I think about corrected expression for >> quick chart to map between kernel space and user space in ftrace . >> >> Steven Rostedt: >> 100 items does not map to 99. Which begs the question, what can have >> internal kernel priority 99? >> >> GeunSik Lim : >> ok. Below example is about kernel (static) priority 99 that you said. >> please, refer >> to http://www.kernel.org/doc/man-pages/online/pages/man2/sched_setscheduler.2.html >> webpage. >> >> For processes scheduled under one of the normal scheduling policies >> (SCHED_OTHER, SCHED_IDLE, SCHED_BATCH), sched_priority is not used in >> scheduling decisions (it must be specified as 0). >> >> int main (int argc, char **argv) >> { int pidnumber, ret; >> struct sched_param p; >> p.sched_priority = 0; <------ Kernel (static) priority. >> if (argc != 2) { >> printf("usage: setbatch <pid>\n"); >> exit(-1); >> } >> pidnumber = atol(argv[1]); >> /* 3 = Number of SCHED_BATCH Constant */ >> ret = sched_setscheduler(pidnumber, 3, &p); >> if (ret) { >> printf("could not set pid %d to SCHED_BATCH: err %d.\n", pid, ret); >> return -1; >> } >> printf("pid %d is SCHED_BATCH from now on.\n", pid); >> return 0; >> } >> >> >> > >> > Processes scheduled with SCHED_OTHER or SCHED_BATCH must be assigned >> > the static priority 0. Processes scheduled under SCHED_FIFO or SCHED_RR >> > can have a static priority in the range 1 to 99. >> > (reference: $> man 2 sched_setscheduler) >> > >> > Signed-off-by: GeunSik Lim <geunsik.lim@xxxxxxxxxxx> >> > >> > diff --git a/Documentation/scheduler/sched-rt-group.txt b/Documentation/scheduler/sched-rt-group.txt >> > index 5ba4d3f..1537146 100644 >> > --- a/Documentation/scheduler/sched-rt-group.txt >> > +++ b/Documentation/scheduler/sched-rt-group.txt >> > @@ -169,7 +169,7 @@ get their allocated time. >> > >> > Implementing SCHED_EDF might take a while to complete. Priority Inheritance is >> > the biggest challenge as the current linux PI infrastructure is geared towards >> > -the limited static priority levels 0-139. With deadline scheduling you need to >> > +the limited static priority levels 0-99. With deadline scheduling you need to >> > do deadline inheritance (since priority is inversely proportional to the >> > deadline delta (deadline - now). > > Note, this document deals with internal kernel manipulations. The "prio" > inside the kernel is indeed 0-139. Actually, if we count the idle task, it > is 0-140. The PI code will also deal with non RT tasks so it is correct to > say that the priority inheritance deals with 0-139 (I don't think the idle > task ever touches anything needing PI). > > The sched_setscheduler user API uses a different priority mapping. I was > looking at the code inside sched.c and I believe this is the mapping: > > > 0 to 98 - maps to RT tasks 99 to 1 (SCHED_RR or SCHED_FIFO) > > 99 - maps to internal kernel threads that want to be lower than RT tasks > but higher than SCHED_OTHER tasks. Although I'm not sure if any > kernel thread actually uses this. I'm not even sure how this can be > set, because the internal sched_setscheduler function does not allow > for it. Thank you for additional explanation about kernel-space static priority 99 in the map of priority values between kernel-space and user-space. I will update like belows. Kernel priority: 0(high) to 98(low) ==> user RT priority 99(high) to 1(low) with SCHED_RR or SCHED_FIFO Kernel priority: 99 ==> sched_priority is not used in scheduling deci sions (it must be specified as 0) Kernel priority: 100(high) to 139(low) ==> user nice -20(high) to 19(low) Kernel priority: 140 ==> idle task priority > > 100 to 139 - maps nice levels -20 to 19. These are not set via > sched_setscheduler, but are set via the nice system call. > > 140 - reserved for idle tasks. > > -- Steve > -- Regards, GeunSik Lim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
