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> 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. 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