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| author | Borislav Petkov <bp@suse.de> | 2021-09-14 22:33:55 +0200 |
|---|---|---|
| committer | Jonathan Corbet <corbet@lwn.net> | 2021-09-27 11:31:11 -0600 |
| commit | 15ce51f55e15d512a8e3467c0bcbb0f49cd42e05 (patch) | |
| tree | 32bd2c8340c04e12c3f31684d3fd2d13126ae1f1 /Documentation/timers/no_hz.rst | |
| parent | 9770a132656cb5462afaedcb645ce5aa256b0ba9 (diff) | |
| download | linux-15ce51f55e15d512a8e3467c0bcbb0f49cd42e05.tar.bz2 | |
Documentation/no_hz: Introduce "dyntick-idle mode" before using it
The CONFIG_NO_HZ_IDLE paragraph is using "dyntick-idle mode" before
having defined it while the definition comes a couple of paragraphs
later.
That is leaving the reader with scratching head what that dyntick-idle
mode might be. Pull its definition up so that it is clear.
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20210914203355.21360-1-bp@alien8.de
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/timers/no_hz.rst')
| -rw-r--r-- | Documentation/timers/no_hz.rst | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/Documentation/timers/no_hz.rst b/Documentation/timers/no_hz.rst index 6cadad7c3aad..20ad23a6c618 100644 --- a/Documentation/timers/no_hz.rst +++ b/Documentation/timers/no_hz.rst @@ -70,6 +70,10 @@ interrupt. After all, the primary purpose of a scheduling-clock interrupt is to force a busy CPU to shift its attention among multiple duties, and an idle CPU has no duties to shift its attention among. +An idle CPU that is not receiving scheduling-clock interrupts is said to +be "dyntick-idle", "in dyntick-idle mode", "in nohz mode", or "running +tickless". The remainder of this document will use "dyntick-idle mode". + The CONFIG_NO_HZ_IDLE=y Kconfig option causes the kernel to avoid sending scheduling-clock interrupts to idle CPUs, which is critically important both to battery-powered devices and to highly virtualized mainframes. @@ -91,10 +95,6 @@ Therefore, systems with aggressive real-time response constraints often run CONFIG_HZ_PERIODIC=y kernels (or CONFIG_NO_HZ=n for older kernels) in order to avoid degrading from-idle transition latencies. -An idle CPU that is not receiving scheduling-clock interrupts is said to -be "dyntick-idle", "in dyntick-idle mode", "in nohz mode", or "running -tickless". The remainder of this document will use "dyntick-idle mode". - There is also a boot parameter "nohz=" that can be used to disable dyntick-idle mode in CONFIG_NO_HZ_IDLE=y kernels by specifying "nohz=off". By default, CONFIG_NO_HZ_IDLE=y kernels boot with "nohz=on", enabling |