Qais reported [1] that iterating over all tasks when rebuilding root
domains for finding out which ones are DEADLINE and need their bandwidth
correctly restored on such root domains can be a costly operation (10+
ms delays on suspend-resume). He proposed we skip rebuilding root
domains for certain operations, but that approach seemed arch specific
and possibly prone to errors, as paths that ultimately trigger a rebuild
might be quite convoluted (thanks Qais for spending time on this!).
This is v3 of an alternative approach (v2 at [4]) to fix the problem.
01/06 - Rename functions deadline with DEADLINE accounting (cleanup
suggested by Qais) - no functional change
02/06 - Bring back cpuset_mutex (so that we have write access to cpusets
from scheduler operations - and we also fix some problems
associated to percpu_cpuset_rwsem)
03/06 - Keep track of the number of DEADLINE tasks belonging to each cpuset
04/06 - Use this information to only perform the costly iteration if
DEADLINE tasks are actually present in the cpuset for which a
corresponding root domain is being rebuilt
05/06 - Create DL BW alloc, free & check overflow interface for bulk
bandwidth allocation/removal - no functional change
06/06 - Fix bandwidth allocation handling for cgroup operation
involving multiple tasks
With respect to the v2 posting [4]
1 - rebase on top of Linus' tree as of today (ac9a78681b92)
2 - add the 'why' to 5/6 changelog - Peter
3 - explicitly say that we need to keep cpuset_mutex a mutex for PI on
2/6 - Peter
This set is also available from
https://github.com/jlelli/linux.git deadline/rework-cpusets
Best,
Juri
1 - https://lore.kernel.org/lkml/20230206221428.2125324-1-qyousef@xxxxxxxxxxx/
2 - RFC https://lore.kernel.org/lkml/20230315121812.206079-1-juri.lelli@xxxxxxxxxx/
3 - v1 https://lore.kernel.org/lkml/20230329125558.255239-1-juri.lelli@xxxxxxxxxx/
4 - v2 https://lore.kernel.org/lkml/20230503072228.115707-1-juri.lelli@xxxxxxxxxx/
Dietmar Eggemann (2):
sched/deadline: Create DL BW alloc, free & check overflow interface
cgroup/cpuset: Free DL BW in case can_attach() fails
Juri Lelli (4):
cgroup/cpuset: Rename functions dealing with DEADLINE accounting
sched/cpuset: Bring back cpuset_mutex
sched/cpuset: Keep track of SCHED_DEADLINE task in cpusets
cgroup/cpuset: Iterate only if DEADLINE tasks are present
include/linux/cpuset.h | 12 +-
include/linux/sched.h | 4 +-
kernel/cgroup/cgroup.c | 4 +
kernel/cgroup/cpuset.c | 244 ++++++++++++++++++++++++++--------------
kernel/sched/core.c | 41 +++----
kernel/sched/deadline.c | 67 ++++++++---
kernel/sched/sched.h | 2 +-
7 files changed, 246 insertions(+), 128 deletions(-)
--
2.40.1
