Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH rcu 1/3] doc: Remove obsolete kernel-per-CPU-kthreads RCU_FAST_NO_HZ advice | Date | Wed, 1 Dec 2021 16:06:40 -0800 |
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This document advises building with both CONFIG_NO_HZ=y and CONFIG_RCU_FAST_NO_HZ=y. However, CONFIG_NO_HZ=y offloads callbacks from all nohz_full CPUs, and CPUs with offloaded callbacks do not benefit from CONFIG_RCU_FAST_NO_HZ=y. Quite the opposite: CONFIG_RCU_FAST_NO_HZ=y simply adds a bit of idle entry/exit overhead.
This commit therefore changes that advice to only CONFIG_NO_HZ=y.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org> --- Documentation/admin-guide/kernel-per-CPU-kthreads.rst | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-per-CPU-kthreads.rst b/Documentation/admin-guide/kernel-per-CPU-kthreads.rst index 5e51ee5b03589..e4a5fc26f1a9d 100644 --- a/Documentation/admin-guide/kernel-per-CPU-kthreads.rst +++ b/Documentation/admin-guide/kernel-per-CPU-kthreads.rst @@ -208,7 +208,7 @@ Do at least one of the following: 2. Enable RCU to do its processing remotely via dyntick-idle by doing all of the following: - a. Build with CONFIG_NO_HZ=y and CONFIG_RCU_FAST_NO_HZ=y. + a. Build with CONFIG_NO_HZ=y. b. Ensure that the CPU goes idle frequently, allowing other CPUs to detect that it has passed through an RCU quiescent state. If the kernel is built with CONFIG_NO_HZ_FULL=y, -- 2.31.1.189.g2e36527f23
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