2009/5/20 Steven Rostedt <rostedt@xxxxxxxxxxx>: > > On Wed, 20 May 2009, GeunSik Lim wrote: > >> >> >> commit 43bf3fdddfd6b0ac65ef59bec3c79d9f9064e8bd >> Author: GeunSik,Lim <leemgs1@xxxxxxxxx> >> Date: Thu May 14 13:39:18 2009 +0900 >> >> ftrace: fix typo in ftrace.txt file. >> >> Fix typo about chart to map the kernel priority to >> user land priorities. >> >> About sched_setscheduler(2) >> Processes scheduled under SCHED_FIFO or SCHED_RR >> can have a static priority in the range 1 to 99. >> >> Signed-off-by: GeunSik Lim <geunsik.lim@xxxxxxxxxxx> >> >> diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt >> index fd9a3e6..0e17632 100644 >> --- a/Documentation/trace/ftrace.txt >> +++ b/Documentation/trace/ftrace.txt >> @@ -518,9 +518,14 @@ priority with zero (0) being the highest priority and the nice >> values starting at 100 (nice -20). Below is a quick chart to map >> the kernel priority to user land priorities. >> >> - Kernel priority: 0 to 99 ==> user RT priority 99 to 0 >> - Kernel priority: 100 to 139 ==> user nice -20 to 19 >> - Kernel priority: 140 ==> idle task priority >> + Kernel priority: 0(high) to 99(low) ==> user RT priority 99(high) to 1(low) > > Shouldn't that be: > > Kernel priority: 0(high) to 98(low) ==> user RT priority 99(high) to 1(low) > Thank you for your opinion. I think about corrected expression for quick chart to map between kernel space and user space in ftrace . > 100 items does not map to 99. Which begs the question, what can have > internal kernel priority 99? > 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; } >> + Kernel priority: 100(high) to 139(low) ==> user nice -20(high) to 19(low) >> + Kernel priority: 140 ==> idle task priority >> + >> +Processes scheduled with SCHED_OTHER or SCHED_BATCH must be assigned >> +the static priority 0. Processes scheduled under SCHED_FIFO or SCHED_RR > > This line is confusing. "static priorty 0" really has no meaning here. > Those now enter the "nice" priorities, and this statement does not > represent what is shown in the ftrace output. > I agree with your opinion about exact understanding of ftrace output. I will remove this additional description to avoid confusing when we use this document as ftrace how to. >> +can have a static priority in the range 1 to 99. >> + (reference: $> man 2 sched_setscheduler) >> > > -- 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
