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Dietmar Eggemann de40f33e78 sched/deadline: Reduce rq lock contention in dl_add_task_root_domain()
dl_add_task_root_domain() is called during sched domain rebuild:

  rebuild_sched_domains_locked()
    partition_and_rebuild_sched_domains()
      rebuild_root_domains()
         for all top_cpuset descendants:
           update_tasks_root_domain()
             for all tasks of cpuset:
               dl_add_task_root_domain()

Change it so that only the task pi lock is taken to check if the task
has a SCHED_DEADLINE (DL) policy. In case that p is a DL task take the
rq lock as well to be able to safely de-reference root domain's DL
bandwidth structure.

Most of the tasks will have another policy (namely SCHED_NORMAL) and
can now bail without taking the rq lock.

One thing to note here: Even in case that there aren't any DL user
tasks, a slow frequency switching system with cpufreq gov schedutil has
a DL task (sugov) per frequency domain running which participates in DL
bandwidth management.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Quentin Perret <qperret@google.com>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20210119083542.19856-1-dietmar.eggemann@arm.com
2021-02-17 14:12:42 +01:00
arch sched: Harden PREEMPT_DYNAMIC 2021-02-17 14:12:42 +01:00
block
certs
crypto
Documentation preempt: Introduce CONFIG_PREEMPT_DYNAMIC 2021-02-17 14:12:24 +01:00
drivers Linux 5.11 2021-02-17 14:04:39 +01:00
fs for-5.11-rc7-tag 2021-02-13 11:55:29 -08:00
include sched: Harden PREEMPT_DYNAMIC 2021-02-17 14:12:42 +01:00
init Linux 5.11 2021-02-17 14:04:39 +01:00
ipc
kernel sched/deadline: Reduce rq lock contention in dl_add_task_root_domain() 2021-02-17 14:12:42 +01:00
lib rbtree, timerqueue: Use rb_add_cached() 2021-02-17 14:08:01 +01:00
LICENSES
mm mm, slub: better heuristic for number of cpus when calculating slab order 2021-02-10 11:19:27 -08:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2021-02-10 11:33:39 -08:00
samples
scripts Kbuild fixes for v5.11 (3rd) 2021-02-14 11:36:32 -08:00
security
sound
tools static_call: Allow module use without exposing static_call_key 2021-02-17 14:12:42 +01:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap MAINTAINERS: update Andrey Ryabinin's email address 2021-02-09 17:26:44 -08:00
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Merge branch 'for-5.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2021-02-13 12:25:42 -08:00
Makefile Linux 5.11 2021-02-14 14:32:24 -08:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.