Time namespace
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Two things (for now) we want to solve with this:
- Shift timer's offsets
- Make start-time remain "unchanged" after C/R
- Continuous flow of monotonic time (CLOCK_MONOTONIC).
What about other kinds of counters like perf events and trace events?
TODO
Required in RFC
- selftests to test all we've added
- TIME_NS iffdefery everywhere
Maybe later
- CLONE_NEWTIME reuses the last free flag from sys_clone() - any way to still keep extensibility for the syscall?
- arm64/arm32/s390/power64 - add archs vvar support (nit: big/little-endianess for timespec::nsec)
- REALTIME-related:
- REALTIME offsets
- vvar offsets will need synchronization (like gtod_read_begin()/gtod_read_retry())
- vfs modification/creation time should work
- starttime in /proc/pid/stat
- btime in /proc/stat
- utime()/utimes()/futimesat() (with times == NULL)
- utimensat()/futimens() - with UTIME_NOW
- mq_timedsend()/mq_timedreceive()
- semtimedop()
- timerfd
- timer_create()
- COARSE times
- clock_nanosleep()
- Adjtime (too complicated for PoC)
- Cpu time for thread/pid/pgid (times())
- /proc/stat ticks? (top uses them e.g.)
- pid creation time (probably different unrelated API)
- clock_tai - if we care about isolation from host's time
Git
Links
- PATCH 00/32 kernel: Introduce Time Namespace
- 11/2018 [Ksummit-discuss] [TECH-TOPIC] Multiple time domains
- 09/2018 LWN: Time namespaces
- 09/2018 RFC 00/20 ns: Introduce Time Namespace
- 06/2018 The progress of Time namespace
- 04/2017 Two Objects not Namespaced by the Linux Kernel
- 00/2017 VirtualTimeKernel
- 00/2016 Article about usage of time namespace in VirtualTimeKernel
- 08/2015 What's missing from upstream kernel containers?
- 09/2009 LPC2009
- 00/2006 Multiple Instances of the Global Linux Namespaces
- 04/2006 LWN: Virtual time