From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
peterz@infradead.org, vincent.guittot@linaro.org
Subject: Re: [PATCH v2 3/9] sched: Remove checks against SD_LOAD_BALANCE
Date: Mon, 23 Mar 2020 15:26:35 +0100 [thread overview]
Message-ID: <5decd96b-6fe0-3c35-4609-59378a0c8621@arm.com> (raw)
In-Reply-To: <jhjv9n0o8hf.mognet@arm.com>
On 19.03.20 13:05, Valentin Schneider wrote:
>
> On Thu, Mar 19 2020, Dietmar Eggemann wrote:
>> On 11.03.20 19:15, Valentin Schneider wrote:
[...]
> Your comments make me realize that changelog isn't great, what about the
> following?
>
> ---
>
> The SD_LOAD_BALANCE flag is set unconditionally for all domains in
> sd_init(). By making the sched_domain->flags syctl interface read-only, we
> have removed the last piece of code that could clear that flag - as such,
> it will now be always present. Rather than to keep carrying it along, we
> can work towards getting rid of it entirely.
>
> cpusets don't need it because they can make CPUs be attached to the NULL
> domain (e.g. cpuset with sched_load_balance=0), or to a partitionned
s/partitionned/partitioned
> root_domain, i.e. a sched_domain hierarchy that doesn't span the entire
> system (e.g. root cpuset with sched_load_balance=0 and sibling cpusets with
> sched_load_balance=1).
>
> isolcpus apply the same "trick": isolated CPUs are explicitly taken out of
> the sched_domain rebuild (using housekeeping_cpumask()), so they get the
> NULL domain treatment as well.
>
> Remove the checks against SD_LOAD_BALANCE.
Sounds better to me:
Essentially, I was referring to examples like:
Hikey960 - 2x4
(A) exclusive cpusets:
root@h960:/sys/fs/cgroup/cpuset# mkdir cs1
root@h960:/sys/fs/cgroup/cpuset# echo 1 > cs1/cpuset.cpu_exclusive
root@h960:/sys/fs/cgroup/cpuset# echo 0 > cs1/cpuset.mems
root@h960:/sys/fs/cgroup/cpuset# echo 0-2 > cs1/cpuset.cpus
root@h960:/sys/fs/cgroup/cpuset# mkdir cs2
root@h960:/sys/fs/cgroup/cpuset# echo 1 > cs2/cpuset.cpu_exclusive
root@h960:/sys/fs/cgroup/cpuset# echo 0 > cs2/cpuset.mems
root@h960:/sys/fs/cgroup/cpuset# echo 3-5 > cs2/cpuset.cpus
root@h960:/sys/fs/cgroup/cpuset# echo 0 > cpuset.sched_load_balance
root@h960:/proc/sys/kernel# tree -d sched_domain
├── cpu0
│ └── domain0
├── cpu1
│ └── domain0
├── cpu2
│ └── domain0
├── cpu3
│ └── domain0
├── cpu4
│ ├── domain0
│ └── domain1
├── cpu5
│ ├── domain0
│ └── domain1
├── cpu6
└── cpu7
(B) non-exclusive cpuset:
root@h960:/sys/fs/cgroup/cpuset# echo 0 > cpuset.sched_load_balance
[ 8661.240385] CPU1 attaching NULL sched-domain.
[ 8661.244802] CPU2 attaching NULL sched-domain.
[ 8661.249255] CPU3 attaching NULL sched-domain.
[ 8661.253623] CPU4 attaching NULL sched-domain.
[ 8661.257989] CPU5 attaching NULL sched-domain.
[ 8661.262363] CPU6 attaching NULL sched-domain.
[ 8661.266730] CPU7 attaching NULL sched-domain.
root@h960:/sys/fs/cgroup/cpuset# mkdir cs1
root@h960:/sys/fs/cgroup/cpuset# echo 0-5 > cs1/cpuset.cpus
root@h960:/proc/sys/kernel# tree -d sched_domain
├── cpu0
│ ├── domain0
│ └── domain1
├── cpu1
│ ├── domain0
│ └── domain1
├── cpu2
│ ├── domain0
│ └── domain1
├── cpu3
│ ├── domain0
│ └── domain1
├── cpu4
│ ├── domain0
│ └── domain1
├── cpu5
│ ├── domain0
│ └── domain1
├── cpu6
└── cpu7
next prev parent reply other threads:[~2020-03-23 14:26 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-11 18:15 [PATCH v2 0/9] sched: Streamline select_task_rq() & select_task_rq_fair() Valentin Schneider
2020-03-11 18:15 ` [PATCH v2 1/9] sched/fair: find_idlest_group(): Remove unused sd_flag parameter Valentin Schneider
2020-03-19 9:05 ` Dietmar Eggemann
2020-03-11 18:15 ` [PATCH v2 2/9] sched/debug: Make sd->flags sysctl read-only Valentin Schneider
2020-03-19 9:07 ` Dietmar Eggemann
2020-03-19 12:04 ` Valentin Schneider
2020-03-11 18:15 ` [PATCH v2 3/9] sched: Remove checks against SD_LOAD_BALANCE Valentin Schneider
2020-03-19 10:28 ` Dietmar Eggemann
2020-03-19 12:05 ` Valentin Schneider
2020-03-23 14:26 ` Dietmar Eggemann [this message]
2020-03-23 17:17 ` Valentin Schneider
2020-03-11 18:15 ` [PATCH v2 4/9] sched/topology: Kill SD_LOAD_BALANCE Valentin Schneider
2020-03-19 10:29 ` Dietmar Eggemann
2020-03-19 12:06 ` Valentin Schneider
2020-03-11 18:15 ` [PATCH v2 5/9] sched: Add WF_TTWU, WF_EXEC wakeup flags Valentin Schneider
2020-03-11 18:15 ` [PATCH v2 6/9] sched: Kill select_task_rq()'s sd_flag parameter Valentin Schneider
2020-03-11 18:15 ` [PATCH v2 7/9] sched/fair: Dissociate wakeup decisions from SD flag value Valentin Schneider
2020-03-11 18:16 ` [PATCH v2 8/9] sched/fair: Split select_task_rq_fair want_affine logic Valentin Schneider
2020-03-19 10:30 ` Dietmar Eggemann
2020-03-19 12:06 ` Valentin Schneider
2020-03-11 18:16 ` [PATCH v2 9/9] sched/topology: Define and use shortcut pointers for wakeup sd_flag scan Valentin Schneider
2020-03-19 10:46 ` Dietmar Eggemann
2020-03-19 12:22 ` Valentin Schneider
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