Also, you can configure the kernel at boot to exclude certain cpus from the OS completely so no process can interfere with them - BUT - processes/threads can still be moved to these isolated cpus using setsched().
> On Sep 27, 2024, at 10:34 AM, robert engels <reng...@ix.netcom.com> wrote: > > What you want to do is start the process with a cset to restrict the cores it > can use - then use the setsched to move certain threads to cores that have > been excluded. > >> On Sep 27, 2024, at 10:26 AM, 'TheDiveO' via golang-nuts >> <golang-nuts@googlegroups.com <mailto:golang-nuts@googlegroups.com>> wrote: >> >> Are you running this on a multi-core? Your non-fifo tasks can be scheduled >> to other cores, et cetera. BTW, fifo 99 is a recipe for desaster as it can >> starve the kernel on a core, preventing necessary kernel house-keeping. >> Don't ask me how I know... >> >> What is the reason for setting GOMAXPROCS, I'm at a loss here, so >> appreciating help! IIRC, OS-thread locked goroutines don't count against >> this limit. >> >> This looks like a situation where I personally would fire off recording >> kernel scheduler tracepoint events and then having a close look at in >> kernelshark at what really is going on. There are syscalls in the FIFO >> scheduled path that might cause preemption. I would look at sched_switch >> here, as well as sched_switch_new. Maybe print the TIDs so you can find your >> go-routine related tasks in all the scheduler event noise, but maybe the >> binary's comm (name) might be already sufficient if you give it a catchy >> name. >> >> A steeper learning curve would be to prepare a bpftrace script matching on >> the comm/name on the scheduler trace events, to get an idea of whats going >> on. >> >> On Thursday, September 26, 2024 at 5:49:53 AM UTC+2 Zhao Weng wrote: >> Hi gophers, >> I'm doing a research on how to prioritise some goroutines over others.So I >> can allocate more CPU resource to more important part of the program. >> I try to do it by calling runtime.LockOSThread to assign the goroutine needs >> to be prioritise to a designated OS thread, and unix.SchedSetAttr to >> prioritise that OS thread. Here is the code: >> >> ```go >> package main >> >> import ( >> "flag" >> "fmt" >> "runtime" >> "sync" >> "time" >> >> "golang.org/x/sys/unix <http://golang.org/x/sys/unix>" >> ) >> >> var ( >> nPrioritizedGoroutines = flag.Int("p", 1, "# of prioritized goroutines") >> nNormalGoroutines = flag.Int("n", 1, "# of normal goroutines") >> restDuration = flag.Duration("r", 0, "rest for a certain >> amount of time between works") >> ) >> >> func prioritizeThread() { >> // set thread priority to the highest >> a := unix.SchedAttr{ >> Size: unix.SizeofSchedAttr, >> Policy: 1, >> Priority: 99, >> } >> >> if err := unix.SchedSetAttr(0, &a, 0); err != nil { >> panic(err) >> } >> } >> >> func doWorks(workerId int) { >> t := time.Now() >> for i := 0; i < 100; i++ { >> st := time.Now() >> res := 0 >> for ii := 0; ii < 1e9; ii++ { >> res += ii >> } >> fmt.Printf("%d@%d, timecost: %s, res: %d \n", workerId, >> unix.Gettid(), time.Since(st), res) >> >> // sleep for a while to simulate gaps between requests. >> if *restDuration > 0 { >> time.Sleep(*restDuration) >> } >> } >> fmt.Printf("total execute time for worker: %d is %s\n", workerId, >> time.Since(t)) >> } >> >> func main() { >> flag.Parse() >> >> runtime.GOMAXPROCS(*nPrioritizedGoroutines) >> var wg sync.WaitGroup >> >> workerId := 0 >> for i := 0; i < *nPrioritizedGoroutines; i++ { >> wg.Add(1) >> go func(workerId int) { >> // assign goroutine to a designated thread >> runtime.LockOSThread() >> // prioritize this thread >> prioritizeThread() >> >> defer wg.Done() >> doWorks(workerId) >> }(workerId) >> workerId++ >> } >> >> for i := 0; i < *nNormalGoroutines; i++ { >> wg.Add(1) >> go func(workerId int) { >> defer wg.Done() >> doWorks(workerId) >> }(workerId) >> workerId++ >> } >> >> wg.Wait() >> } >> ``` >> compile on linux, and run with command `sudo ./sche`, it seems not working, >> CPU resource is shared by two thread, and two goroutine execute `doWorks` in >> similar timecost(1.5 seconds). >> >> sudo ./sche >> 1@255429, timecost: 1.475347182s, res: 499999999500000000 >> 0@255425, timecost: 1.517077413s, res: 499999999500000000 >> 1@255429, timecost: 1.473167148s, res: 499999999500000000 >> 0@255425, timecost: 1.515322146s, res: 499999999500000000 >> 1@255429, timecost: 1.494751901s, res: 499999999500000000 >> 0@255425, timecost: 1.532692691s, res: 499999999500000000 >> >> while with 1 goroutine only, the timecost will be 0.75 seconds >> >> sudo ./sche -n 0 >> 0@257072, timecost: 751.18938ms, res: 499999999500000000 >> 0@257072, timecost: 747.364725ms, res: 499999999500000000 >> 0@257072, timecost: 745.362553ms, res: 499999999500000000 >> 0@257072, timecost: 748.353778ms, res: 499999999500000000 >> >> Am I doing anything wrong here? >> >> Zhao Weng >> >> -- >> You received this message because you are subscribed to the Google Groups >> "golang-nuts" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to golang-nuts+unsubscr...@googlegroups.com >> <mailto:golang-nuts+unsubscr...@googlegroups.com>. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/golang-nuts/27ad2fb1-97df-43eb-84a9-1c83669ad2e2n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/golang-nuts/27ad2fb1-97df-43eb-84a9-1c83669ad2e2n%40googlegroups.com?utm_medium=email&utm_source=footer>. > > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com > <mailto:golang-nuts+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/golang-nuts/1EA11541-07A1-4A85-8775-F256EC2338EB%40ix.netcom.com > > <https://groups.google.com/d/msgid/golang-nuts/1EA11541-07A1-4A85-8775-F256EC2338EB%40ix.netcom.com?utm_medium=email&utm_source=footer>. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/D62182F1-98FD-4E89-AD7E-72BCCABCBB97%40ix.netcom.com.
