From 0bef253ec5b526747861a65518ecd3216b839915 Mon Sep 17 00:00:00 2001 From: Michael Kerrisk Date: Tue, 9 Oct 2018 11:45:43 +0200 Subject: [PATCH] cgroups.7: Add more detail on v2 'cpu' controller and realtime threads Explicitly note the scheduling policies that are relevant for the v2 'cpu' controller. Signed-off-by: Michael Kerrisk --- man7/cgroups.7 | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/man7/cgroups.7 b/man7/cgroups.7 index f6ea348ff..5ab1070da 100644 --- a/man7/cgroups.7 +++ b/man7/cgroups.7 @@ -1541,8 +1541,17 @@ so as to minimize the (small) cost of traversing the cgroup hierarchy. .SS The cgroups v2 """cpu""" controller and realtime processes As at Linux 4.15, the cgroups v2 .I cpu -controller does not support control of realtime processes, -and the controller can be enabled in the root cgroup only +controller does not support control of realtime threads +(specifically threads scheduled under any of the policies +.BR SCHED_FIFO , +.BR SCHED_RR , +described +.BR SCHED_DEADLINE ; +see +.BR sched (7)). +Therefore, the +.I cpu +controller can be enabled in the root cgroup only if all realtime threads are in the root cgroup. (If there are realtime processes in nonroot cgroups, then a .BR write (2)