Hi Vignesh, Thank you. I understood from your description that SCHED_SOFTIRQ has no relation with scheduling directly but only deals with load balancing between groups. I have one more question regarding timer interrupts and its relation to schedule() function. As I said, my understanding was that schedule() function is invoked in 2 cases 1. When a process goes to sleep or waiting for a resource 2. For each timer tick Regarding point 2, I am still not clear how each timer tick invokes the scheduler.Please give any pointers On Wed, Jan 28, 2015 at 11:23 PM, Vignesh Radhakrishnan <vignesh1192@xxxxxxxxx> wrote: > Hey Sreejith, > > > softirq's are run as bottom half processing (after an interrupt is handled > or when there is no work to be done - > https://www.kernel.org/doc/htmldocs/kernel-hacking/basics-softirqs.html ) > and sched_softirq is one such soft irq whose only function is confined to > the routine run_rebalance_domain(). > > > __schedule() is the main scheduling function that tries to pick the next > task and then perform context switch and other associated scheduling > functions. Since run_rebalance_domain() need not be run at that exact time > frame, it is scheduled for later time when the cpu can take it up using > softirq's. Therefore __schedule() need not be called in this softirq context > as such because these are independent operations. > > Hope this helps. > > Thanks and regards, > Vignesh Radhakrishnan > > On Wed, Jan 28, 2015 at 10:25 PM, Sreejith M M <sreejith.mm@xxxxxxxxx> > wrote: >> >> Hi, >> >> I was reading LKD by Robert Love. I got the following idea from the book. >> >> >> Correct me if I am worng >> I was checking through source code and I found that on every timer >> interrupt, through sched/fair.c we are raising the SCHED_SOFTIRQ(). >> I was checking the relation between SCHED_SOFTIRQ and actual >> __schedule() function. >> >> My assumption: >> schedule() function is the function which selects the processes which >> are ready to run in run queue. schedule() function is called in every >> timer tick. >> >> What I was thinking is that schedule() will be called as part of >> handling SCHED_SOFTIRQ() . But in source code, SCHED_SOFTIRQ is >> handled through run_rebalance_domain() function (sched/fair.c) . I am >> unable to trace __schedule() from this function. >> >> Am I missing anything or my assumptions are wrong? >> -- >> Regards, >> Sreejith >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies@xxxxxxxxxxxxxxxxx >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > > > -- > http://vigneshradhakrishnan.blogspot.com/ -- Regards, Sreejith _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
