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Commit c2519784 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

documentation: Update NO_HZ_FULL interaction with POSIX timers 



POSIX timers are no longer starved on adaptive-ticks CPUs.  Instead, they
prevent affected CPUs from entering adaptive-ticks mode.  This commit
therefore updates the NO_HZ.txt documentation.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 89bf5d82

Documentation/timers/NO_HZ.txt

+3 −7
Original line number Original line Diff line number Diff line
@@ -158,13 +158,9 @@ not come for free: 
	to the need to inform kernel subsystems (such as RCU) about

	to the need to inform kernel subsystems (such as RCU) about

	the change in mode.

	the change in mode.





3.	POSIX CPU timers on adaptive-tick CPUs may miss their deadlines

3.	POSIX CPU timers prevent CPUs from entering adaptive-tick mode.

	(perhaps indefinitely) because they currently rely on

	Real-time applications needing to take actions based on CPU time

	scheduling-tick interrupts.  This will likely be fixed in

	consumption need to use other means of doing so.

	one of two ways: (1) Prevent CPUs with POSIX CPU timers from

	entering adaptive-tick mode, or (2) Use hrtimers or other

	adaptive-ticks-immune mechanism to cause the POSIX CPU timer to

	fire properly.





4.	If there are more perf events pending than the hardware can

4.	If there are more perf events pending than the hardware can

	accommodate, they are normally round-robined so as to collect

	accommodate, they are normally round-robined so as to collect