From: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
To: "Peter Zijlstra (Intel)" <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>
Cc: Ricardo Neri <ricardo.neri@intel.com>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Ben Segall <bsegall@google.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Len Brown <len.brown@intel.com>, Mel Gorman <mgorman@suse.de>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Steven Rostedt <rostedt@goodmis.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
Valentin Schneider <vschneid@redhat.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Subject: [PATCH 0/4] sched/fair: Avoid unnecessary migrations within SMT domains
Date: Thu, 25 Aug 2022 15:55:25 -0700 [thread overview]
Message-ID: <20220825225529.26465-1-ricardo.neri-calderon@linux.intel.com> (raw)
Intel processors that support Intel Turbo Boost Max 3.0 use asym_packing
to assign higher priorities to CPUs with higher maximum frequencies. It
artificially assigns, however, a lower priority to the higher-numbered
SMT siblings to ensure that they are used last.
This results in unnecessary task migrations within the SMT domains.
On processors with a mixture of higher-frequency SMT cores and lower-
frequency non-SMT cores (such as Intel hybrid processors), a lower-
priority CPU pulls tasks from the higher-priority cores if more than one
SMT sibling is busy.
Do not use different priorities for each SMT sibling. Instead, tweak the
asym_packing load balancer to recognize SMT cores with more than one
busy sibling and let lower-priority CPUs pull tasks.
Removing these artificial priorities avoids superfluous migrations and
lets lower-priority cores inspect all SMT siblings for the busiest queue.
Thanks and BR,
Ricardo
Ricardo Neri (4):
sched/fair: Simplify asym_packing logic for SMT sched groups
sched/fair: Do not disqualify either runqueues of SMT sched groups
sched/fair: Let lower-priority CPUs do active balancing
x86/sched: Avoid unnecessary migrations within SMT domains
arch/x86/kernel/itmt.c | 23 +++++-----------------
kernel/sched/fair.c | 44 ++++++++++++++++++++----------------------
2 files changed, 26 insertions(+), 41 deletions(-)
--
2.25.1
next reply other threads:[~2022-08-25 22:49 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-25 22:55 Ricardo Neri [this message]
2022-08-25 22:55 ` [PATCH 1/4] sched/fair: Simplify asym_packing logic for SMT sched groups Ricardo Neri
2022-10-18 9:34 ` Peter Zijlstra
2022-10-20 1:25 ` Ricardo Neri
2022-08-25 22:55 ` [PATCH 2/4] sched/fair: Do not disqualify either runqueues of " Ricardo Neri
2022-08-25 22:55 ` [PATCH 3/4] sched/fair: Let lower-priority CPUs do active balancing Ricardo Neri
2022-08-25 22:55 ` [PATCH 4/4] x86/sched: Avoid unnecessary migrations within SMT domains Ricardo Neri
2022-10-18 2:35 ` [PATCH 0/4] sched/fair: " Ricardo Neri
2022-10-18 9:40 ` Peter Zijlstra
2022-10-20 1:38 ` Ricardo Neri
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=20220825225529.26465-1-ricardo.neri-calderon@linux.intel.com \
--to=ricardo.neri-calderon@linux.intel.com \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=dietmar.eggemann@arm.com \
--cc=juri.lelli@redhat.com \
--cc=len.brown@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=peterz@infradead.org \
--cc=rafael.j.wysocki@intel.com \
--cc=ravi.v.shankar@intel.com \
--cc=ricardo.neri@intel.com \
--cc=rostedt@goodmis.org \
--cc=srinivas.pandruvada@linux.intel.com \
--cc=tim.c.chen@linux.intel.com \
--cc=vincent.guittot@linaro.org \
--cc=vschneid@redhat.com \
--cc=x86@kernel.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).