From: Valentin Schneider <valentin.schneider@arm.com>
To: Steve Sistare <steven.sistare@oracle.com>,
mingo@redhat.com, peterz@infradead.org
Cc: subhra.mazumdar@oracle.com, dhaval.giani@oracle.com,
daniel.m.jordan@oracle.com, pavel.tatashin@microsoft.com,
matt@codeblueprint.co.uk, umgwanakikbuti@gmail.com,
riel@redhat.com, jbacik@fb.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, quentin.perret@arm.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 03/10] sched/topology: Provide cfs_overload_cpus bitmap
Date: Mon, 12 Nov 2018 16:42:11 +0000 [thread overview]
Message-ID: <de2d2824-d66e-8852-d67a-d58b478b74c1@arm.com> (raw)
In-Reply-To: <1541767840-93588-4-git-send-email-steven.sistare@oracle.com>
Hi Steve,
On 09/11/2018 12:50, Steve Sistare wrote:
> From: Steve Sistare <steve.sistare@oracle.com>
>
> Define and initialize a sparse bitmap of overloaded CPUs, per
> last-level-cache scheduling domain, for use by the CFS scheduling class.
> Save a pointer to cfs_overload_cpus in the rq for efficient access.
>
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> ---
> include/linux/sched/topology.h | 1 +
> kernel/sched/sched.h | 2 ++
> kernel/sched/topology.c | 21 +++++++++++++++++++--
> 3 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
> index 6b99761..b173a77 100644
> --- a/include/linux/sched/topology.h
> +++ b/include/linux/sched/topology.h
> @@ -72,6 +72,7 @@ struct sched_domain_shared {
> atomic_t ref;
> atomic_t nr_busy_cpus;
> int has_idle_cores;
> + struct sparsemask *cfs_overload_cpus;
Thinking about misfit stealing, we can't use the sd_llc_shared's because
on big.LITTLE misfit migrations happen across LLC domains.
I was thinking of adding a misfit sparsemask to the root_domain, but
then I thought we could do the same thing for cfs_overload_cpus.
By doing so we'd have a single source of information for overloaded CPUs,
and we could filter that down during idle balance - you mentioned earlier
wanting to try stealing at each SD level. This would also let you get
rid of [PATCH 02].
The main part of try_steal() could then be written down as something like
this:
----->8-----
for_each_domain(this_cpu, sd) {
span = sched_domain_span(sd)
for_each_sparse_wrap(src_cpu, overload_cpus) {
if (cpumask_test_cpu(src_cpu, span) &&
steal_from(dts_rq, dst_rf, &locked, src_cpu)) {
stolen = 1;
goto out;
}
}
}
------8<-----
We could limit the stealing to stop at the highest SD_SHARE_PKG_RESOURCES
domain for now so there would be no behavioural change - but we'd
factorize the #ifdef SCHED_SMT bit. Furthermore, the door would be open
to further stealing.
What do you think?
[...]
next prev parent reply other threads:[~2018-11-12 16:42 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-09 12:50 [PATCH v3 00/10] steal tasks to improve CPU utilization Steve Sistare
2018-11-09 12:50 ` [PATCH v3 01/10] sched: Provide sparsemask, a reduced contention bitmap Steve Sistare
2018-11-27 15:16 ` Steven Sistare
2018-11-28 1:19 ` Omar Sandoval
2018-12-06 16:07 ` Steven Sistare
2018-12-06 18:19 ` Omar Sandoval
2018-11-09 12:50 ` [PATCH v3 02/10] sched/topology: Provide hooks to allocate data shared per LLC Steve Sistare
2018-11-09 12:50 ` [PATCH v3 03/10] sched/topology: Provide cfs_overload_cpus bitmap Steve Sistare
2018-11-09 17:38 ` Valentin Schneider
2018-11-19 17:32 ` Steven Sistare
2018-11-20 12:52 ` Valentin Schneider
2018-11-12 16:42 ` Valentin Schneider [this message]
2018-11-19 17:33 ` Steven Sistare
2018-11-20 12:42 ` Valentin Schneider
2018-11-26 19:06 ` Steven Sistare
2018-12-03 16:56 ` Valentin Schneider
2018-12-06 16:40 ` Steven Sistare
2018-12-06 17:28 ` Valentin Schneider
2018-11-09 12:50 ` [PATCH v3 04/10] sched/fair: Dynamically update cfs_overload_cpus Steve Sistare
2018-11-09 12:50 ` [PATCH v3 05/10] sched/fair: Hoist idle_stamp up from idle_balance Steve Sistare
2018-11-09 19:07 ` Valentin Schneider
2018-11-19 17:31 ` Steven Sistare
2018-11-20 10:24 ` Valentin Schneider
2018-11-09 12:50 ` [PATCH v3 06/10] sched/fair: Generalize the detach_task interface Steve Sistare
2018-11-09 12:50 ` [PATCH v3 07/10] sched/fair: Provide can_migrate_task_llc Steve Sistare
2018-11-09 12:50 ` [PATCH v3 08/10] sched/fair: Steal work from an overloaded CPU when CPU goes idle Steve Sistare
2018-11-09 12:50 ` [PATCH v3 09/10] sched/fair: disable stealing if too many NUMA nodes Steve Sistare
2018-11-09 12:50 ` [PATCH v3 10/10] sched/fair: Provide idle search schedstats Steve Sistare
2018-11-10 17:08 ` kbuild test robot
2018-11-09 15:02 ` hackbench run scripts Steven Sistare
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=de2d2824-d66e-8852-d67a-d58b478b74c1@arm.com \
--to=valentin.schneider@arm.com \
--cc=daniel.m.jordan@oracle.com \
--cc=dhaval.giani@oracle.com \
--cc=jbacik@fb.com \
--cc=juri.lelli@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=matt@codeblueprint.co.uk \
--cc=mingo@redhat.com \
--cc=pavel.tatashin@microsoft.com \
--cc=peterz@infradead.org \
--cc=quentin.perret@arm.com \
--cc=riel@redhat.com \
--cc=steven.sistare@oracle.com \
--cc=subhra.mazumdar@oracle.com \
--cc=umgwanakikbuti@gmail.com \
--cc=vincent.guittot@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).