Bug 99401
| Summary: | /proc/timer_list prints out raw kernel jiffies | ||
|---|---|---|---|
| Product: | Timers | Reporter: | William Breathitt Gray (vilhelm.gray) |
| Component: | Other | Assignee: | john stultz (john.stultz) |
| Status: | CLOSED INVALID | ||
| Severity: | low | ||
| Priority: | P1 | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Kernel Version: | 4.0.4 | Subsystem: | |
| Regression: | No | Bisected commit-id: | |
This is not a bug; behaviour is intentional. To quote TThomas Gleixner (http://lkml.org/lkml/2015/8/22/86): > All instances which are de facto APIs, syscalls and also various files > in proc/ must be in USER_HZ because userspace applications depend on > the USER_HZ value. > > proc/timer_list is exempt from that because its more a debugging > interface which is not part of the strict kernel API. And we really > want to see the real values and not the scaled USER_HZ ones for that > purpose. I hope that answers your question. |
I noticed that the “jiffies” line from the /proc/timer_list file has a value that is not scaled via the USER_HZ constant. Looking into the source code of the kernel/time/timer_list.c file, I found lines 189-190 to be the cause: SEQ_printf(m, "jiffies: %Lu\n", (unsigned long long)jiffies); The actual kernel jiffies are printed out directly without scaling. I was under the impression that all kernel jiffies should be scaled via USER_HZ -- e.g. through the jiffies_to_clock_t function provided by include/linux/jiffies.h -- before exposure in userspace. Is my impression correct? If not, when are kernel jiffies scaled via USER_HZ, and when are they not?