Time namespace

The time namespace support has been merged in the 5.6 kernel. The current implementation allows setting per-namespace offsets to the system monotonic and boot-time clocks.

The time namespace support in CRIU has been merged in the 3.14 release.

TODO

Maybe later

• Make start-time remain "unchanged" after C/R
• 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()
• 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
• What about other kinds of counters like perf events and trace events?

Links

• 04/2020 [PATCH v3 0/6] arm64: add the time namespace support
• 01/2020 [GIT pull] timers/core for 5.6-rc1
• 11/2019 PATCHv8 00/34 kernel: Introduce Time Namespace
• 02/2019 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