| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20230314235403.GB30287@ranerica-svr.sc.intel.com>
Date: Tue, 14 Mar 2023 16:54:03 -0700
From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To: Tim Chen <tim.c.chen@...ux.intel.com>
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Ricardo Neri <ricardo.neri@...el.com>,
"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
Ben Segall <bsegall@...gle.com>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Len Brown <len.brown@...el.com>, Mel Gorman <mgorman@...e.de>,
"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
Steven Rostedt <rostedt@...dmis.org>,
Valentin Schneider <vschneid@...hat.com>,
Ionela Voinescu <ionela.voinescu@....com>, x86@...nel.org,
linux-kernel@...r.kernel.org, "Tim C . Chen" <tim.c.chen@...el.com>
Subject: Re: [PATCH v3 04/10] sched/fair: Let low-priority cores help
high-priority busy SMT cores
On Thu, Mar 09, 2023 at 04:51:35PM -0800, Tim Chen wrote:
> On Mon, 2023-02-06 at 20:58 -0800, Ricardo Neri wrote:
> > Using asym_packing priorities within an SMT core is straightforward.
> > Just
> > follow the priorities that hardware indicates.
> >
> > When balancing load from an SMT core, also consider the idle of its
> > siblings. Priorities do not reflect that an SMT core divides its
> > throughput
> > among all its busy siblings. They only makes sense when exactly one
> > sibling
> > is busy.
> >
> > Indicate that active balance is needed if the destination CPU has
> > lower
> > priority than the source CPU but the latter has busy SMT siblings.
> >
> > Make find_busiest_queue() not skip higher-priority SMT cores with
> > more than
> > busy sibling.
> >
> > Cc: Ben Segall <bsegall@...gle.com>
> > Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
> > Cc: Dietmar Eggemann <dietmar.eggemann@....com>
> > Cc: Len Brown <len.brown@...el.com>
> > Cc: Mel Gorman <mgorman@...e.de>
> > Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Cc: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> > Cc: Steven Rostedt <rostedt@...dmis.org>
> > Cc: Tim C. Chen <tim.c.chen@...el.com>
> > Cc: Valentin Schneider <vschneid@...hat.com>
> > Cc: x86@...nel.org
> > Cc: linux-kernel@...r.kernel.org
> > Suggested-by: Valentin Schneider <vschneid@...hat.com>
> > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> > ---
> > Changes since v2:
> > * Introduced this patch.
> >
> > Changes since v1:
> > * N/A
> > ---
> > kernel/sched/fair.c | 31 ++++++++++++++++++++++++++-----
> > 1 file changed, 26 insertions(+), 5 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 80c86462c6f6..c9d0ddfd11f2 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -10436,11 +10436,20 @@ static struct rq *find_busiest_queue(struct
> > lb_env *env,
> > nr_running == 1)
> > continue;
> >
> > - /* Make sure we only pull tasks from a CPU of lower
> > priority */
> > + /*
> > + * Make sure we only pull tasks from a CPU of lower
> > priority
> > + * when balancing between SMT siblings.
> > + *
> > + * If balancing between cores, let lower priority
> > CPUs help
> > + * SMT cores with more than one busy sibling.
> > + */
> > if ((env->sd->flags & SD_ASYM_PACKING) &&
> > sched_asym_prefer(i, env->dst_cpu) &&
> > - nr_running == 1)
> > - continue;
> > + nr_running == 1) {
> > + if (env->sd->flags & SD_SHARE_CPUCAPACITY ||
> > + (!(env->sd->flags & SD_SHARE_CPUCAPACITY)
> > && is_core_idle(i)))
> > + continue;
> > + }
> >
> > switch (env->migration_type) {
> > case migrate_load:
> > @@ -10530,8 +10539,20 @@ asym_active_balance(struct lb_env *env)
> > * lower priority CPUs in order to pack all tasks in the
> > * highest priority CPUs.
> > */
> > - return env->idle != CPU_NOT_IDLE && (env->sd->flags &
> > SD_ASYM_PACKING) &&
> > - sched_asym_prefer(env->dst_cpu, env->src_cpu);
> > + if (env->idle != CPU_NOT_IDLE && (env->sd->flags &
> > SD_ASYM_PACKING)) {
> > + /* Always obey priorities between SMT siblings. */
> > + if (env->sd->flags & SD_SHARE_CPUCAPACITY)
> > + return sched_asym_prefer(env->dst_cpu, env-
> > >src_cpu);
> > +
> > + /*
> > + * A lower priority CPU can help an SMT core with
> > more than one
> > + * busy sibling.
> > + */
> > + return sched_asym_prefer(env->dst_cpu, env->src_cpu)
> > ||
> > + !is_core_idle(env->src_cpu);
> > + }
>
> Suppose we have the Atom cores in a sched group (e.g. a cluster),
> this will pull the tasks from those core to a SMT thread even if
> its sibling thread is busy. Suggest this change
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index da1afa99cd55..b671cb0d7ab3 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -10473,9 +10473,11 @@ asym_active_balance(struct lb_env *env)
> /*
> * A lower priority CPU can help an SMT core with more than one
> * busy sibling.
> + * Pull only if no SMT sibling busy.
> */
> - return sched_asym_prefer(env->dst_cpu, env->src_cpu) ||
> - !is_core_idle(env->src_cpu);
> + if (is_core_idle(env->dst_cpu))
> + return sched_asym_prefer(env->dst_cpu, env->src_cpu) ||
> + !is_core_idle(env->src_cpu);
Thank you Tim! Patch 3 does this check for asym_packing, but we could land
from other types of idle load balancing.
I wil integrate this change to the series.
Thanks and BR,
Ricardo
Powered by blists - more mailing lists