a7y18lte-ubports/android_kernel_samsung_universal7885
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

documentation: Update NO_HZ_FULL interaction with POSIX timers

Browse Source 
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: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2015-01-25 11:28:28 -08:00
parent 89bf5d82ed
commit c25197841e
1 changed files with 3 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
Documentation/timers/NO_HZ.txt
View File

@ -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