convert mach tick units to nsecs

[rmalouf]

Summary

• OS: macOS 11.4
• Bug fix: yes
• Type: core
• Fixes: [macOS / M1] cpu_percent() gives incorrect information #1956, Apple M1, glances shows wrong cpu usage for processes. nicolargo/glances#1827

Description

{{{
Mach sys calls report cpu time in "tick units" -- on intel cpus, these happen to be nsecs but on M1 machines they're about 40 nsecs. This PR corrects for this, but I think it still needs two improvements: the value of mach_timebase_info should be cached somewhere, and there are probably other places where the code depends on 1 tick=1 nsec that also need to be updated. Sounds reasonable? I can work on both of those, but I wanted to get some feedback first before I spend any more time on this.
}}}

[giampaolo]

Shouldn't this be executed on M1 only (if M1 {do_this} else {do_old_stuff})?

[rmalouf]

No, that's not necessary: mach_timebase_info will always give you a valid conversion factor, even if it happens to be 1/1.

[giampaolo]

(closing & reopening to trigger a CI test run)

[giampaolo]

(closing & reopening to trigger a CI test run)

[giampaolo]

@rmalouf looks like there are compilation issues:

2021-10-02T09:27:47.8665360Z   psutil/_psutil_osx.c:224:25: error: use of undeclared identifier 'info'; did you mean 'sinf'?
2021-10-02T09:27:47.8666080Z       mach_timebase_info(&info);
2021-10-02T09:27:47.8666510Z                           ^~~~
2021-10-02T09:27:47.8666870Z                           sinf
2021-10-02T09:27:47.8668040Z   /Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/math.h:328:14: note: 'sinf' declared here
2021-10-02T09:27:47.8668860Z   extern float sinf(float);
2021-10-02T09:27:47.8669250Z                ^
2021-10-02T09:27:47.8670190Z   psutil/_psutil_osx.c:225:39: error: use of undeclared identifier 'info'
2021-10-02T09:27:47.8670860Z       total_user = pti.pti_total_user * info.numer;
2021-10-02T09:27:47.8671370Z                                         ^
2021-10-02T09:27:47.8672280Z   psutil/_psutil_osx.c:226:19: error: use of undeclared identifier 'info'
2021-10-02T09:27:47.8672930Z       total_user /= info.denom;
2021-10-02T09:27:47.8673330Z                     ^
2021-10-02T09:27:47.8674210Z   psutil/_psutil_osx.c:227:43: error: use of undeclared identifier 'info'
2021-10-02T09:27:47.8675150Z       total_system = pti.pti_total_system * info.numer;
2021-10-02T09:27:47.8675680Z                                             ^
2021-10-02T09:27:47.8676670Z   psutil/_psutil_osx.c:228:21: error: use of undeclared identifier 'info'
2021-10-02T09:27:47.8677690Z       total_system /= info.denom;
2021-10-02T09:27:47.8678100Z                       ^
2021-10-02T09:27:47.8678490Z   5 errors generated.
2021-10-02T09:27:47.8679390Z   error: command 'gcc' failed with exit status 1

[odormond]

Hi @giampaolo!

The compilation error is fixed for me by applying the following patch:

diff --git a/psutil/_psutil_osx.c b/psutil/_psutil_osx.c
index 67a52aa9..2effa0a0 100644
--- a/psutil/_psutil_osx.c
+++ b/psutil/_psutil_osx.c
@@ -214,6 +214,7 @@ static PyObject *
 psutil_proc_pidtaskinfo_oneshot(PyObject *self, PyObject *args) {
     pid_t pid;
     struct proc_taskinfo pti;
+    struct mach_timebase_info info;
     uint64_t total_user, total_system;
 
     if (! PyArg_ParseTuple(args, _Py_PARSE_PID, &pid))

I have only tested it on Intel mac yet but will give it a shot tomorrow on M1.

[odormond]

I have only tested it on Intel mac yet but will give it a shot tomorrow on M1.

I finally managed to get my hands on an M1 and I can now confirm that this works.

I've tested it on intel Monterey with python 3.9.6 from brew and M1 BigSur with python 3.8.2 from Apple.

[giampaolo]

Closing this out since it's been outdated / fixed by #2011.