Changes

553 bytes removed , 14:53, 29 April 2020

remove TODO, add LWN link

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~~Two things (for now) we want~~ to ~~solve with this:~~

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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.

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~~# Shift timer's offsets~~

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~~# Make start~~-time ~~remain "unchanged" after C/R~~

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~~# Continuous flow of monotonic time (CLOCK_MONOTONIC)~~.

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~~What about other kinds of counters like perf events and trace events?~~

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[https://github.com/checkpoint-restore/criu/pull/1002 The time namespace support] in CRIU has been merged in the [[Download/criu/3.14 | 3.14 release]].

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~~=TODO=~~

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[https://lwn.net/Articles/766089/ LWN article about time namespaces]

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~~==Required in RFC==~~

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* selftests to test all we've added

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* TIME_NS iffdefery everywhere

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~~==Maybe later==~~

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* CLONE_NEWTIME reuses the last free flag from sys_clone() - any way to still keep extensibility for the syscall?

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* arm64/arm32/s390/power64 - add archs vvar support (nit: big/little-endianess for timespec::nsec)

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* REALTIME-related:

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** REALTIME offsets

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** vvar offsets will need synchronization (like gtod_read_begin()/gtod_read_retry())

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** vfs modification/creation time should work

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** starttime in /proc/pid/stat

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** btime in /proc/stat

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** utime()/utimes()/futimesat() (with times == NULL)

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** utimensat()/futimens() - with UTIME_NOW

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** mq_timedsend()/mq_timedreceive()

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** semtimedop()

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** timerfd

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** timer_create()

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** COARSE times

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** clock_nanosleep()

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* Adjtime (too complicated for PoC)

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* Cpu time for thread/pid/pgid (times())

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* /proc/stat ticks? (top uses them e.g.)

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* pid creation time (probably different unrelated API)

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* clock_tai - if we care about isolation from host's time

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~~=Git=~~

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* [https://~~github~~.~~com~~/~~0x7f454c46~~/~~linux/tree/wip/time-ns https://github.com/0x7f454c46/linux/tree/wip~~/time~~-ns~~]

=Links=

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* [https://lkml.kernel.org/r/20190206001107.16488-1-dima@arista.com PATCH 00/32 kernel: Introduce Time Namespace]

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* [https://lwn.net/Articles/817650/ 04/2020 <nowiki>[PATCH v3 0/6] arm64: add the time namespace support</nowiki>]

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* [https://lore.kernel.org/lkml/158016896588.31887.14143226032971732742.tglx@nanos.tec.linutronix.de/ 01/2020<nowiki> [GIT pull] timers/core for 5.6-rc1</nowiki>]

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* [https://lkml.kernel.org/r/20191112012724.250792-1-dima@arista.com 11/2019 PATCHv8 00/34 kernel: Introduce Time Namespace]

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* [https://lkml.kernel.org/r/20190206001107.16488-1-dima@arista.com 02/2019 PATCH 00/32 kernel: Introduce Time Namespace]

* [https://lists.linuxfoundation.org/pipermail/ksummit-discuss/2018-November/006210.html 11/2018 <nowiki>[Ksummit-discuss] [TECH-TOPIC] Multiple time domains</nowiki>]

* [https://lwn.net/Articles/766089/ 09/2018 LWN: Time namespaces]

Dsafonov

105

edits

Changes

Time namespace (edit)

Revision as of 14:53, 29 April 2020