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8b2383f5c1
This fix tries to address issues raised in #23768 where the CPU count is not updated after cpu ho-plugging. This fix follows the suggestion from #23768 and replace go's `runtime.NumCPU()` with `sysconf(_SC_NPROCESSORS_ONLN)` so that correct CPU count could be obtained even after CPU hot-plugging. This fix is tested manually, as is suggested in #23768. This fix fixes #23768. The NumCPU() in Linux is based on @wmark 's implementation. Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
55 lines
1.2 KiB
Go
55 lines
1.2 KiB
Go
// +build linux
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package sysinfo
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import (
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"runtime"
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"syscall"
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"unsafe"
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"golang.org/x/sys/unix"
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)
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// Returns bit count of 1
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func popcnt(x uint64) (n byte) {
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x -= (x >> 1) & 0x5555555555555555
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x = (x>>2)&0x3333333333333333 + x&0x3333333333333333
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x += x >> 4
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x &= 0x0f0f0f0f0f0f0f0f
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x *= 0x0101010101010101
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return byte(x >> 56)
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}
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// numCPU queries the system for the count of threads available
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// for use to this process.
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//
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// Issues two syscalls.
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// Returns 0 on errors. Use |runtime.NumCPU| in that case.
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func numCPU() int {
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// Gets the affinity mask for a process: The very one invoking this function.
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pid, _, _ := syscall.RawSyscall(unix.SYS_GETPID, 0, 0, 0)
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var mask [1024 / 64]uintptr
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_, _, err := syscall.RawSyscall(unix.SYS_SCHED_GETAFFINITY, pid, uintptr(len(mask)*8), uintptr(unsafe.Pointer(&mask[0])))
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if err != 0 {
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return 0
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}
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// For every available thread a bit is set in the mask.
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ncpu := 0
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for _, e := range mask {
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if e == 0 {
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continue
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}
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ncpu += int(popcnt(uint64(e)))
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}
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return ncpu
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}
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// NumCPU returns the number of CPUs which are currently online
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func NumCPU() int {
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if ncpu := numCPU(); ncpu > 0 {
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return ncpu
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}
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return runtime.NumCPU()
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}
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