From: Ingo Molnar <mingo@kernel.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] sched: Provide a pointer to the valid CPU mask
Date: Thu, 2 May 2019 17:10:55 +0200 [thread overview]
Message-ID: <20190502151055.GA50195@gmail.com> (raw)
In-Reply-To: <20190423142636.14347-1-bigeasy@linutronix.de>
* Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
> In commit 4b53a3412d66 ("sched/core: Remove the tsk_nr_cpus_allowed()
> wrapper") the tsk_nr_cpus_allowed() wrapper was removed. There was not
> much difference in !RT but in RT we used this to implement
> migrate_disable(). Within a migrate_disable() section the CPU mask is
> restricted to single CPU while the "normal" CPU mask remains untouched.
>
> As an alternative implementation Ingo suggested to use
> struct task_struct {
> const cpumask_t *cpus_ptr;
> cpumask_t cpus_mask;
> };
> with
> t->cpus_allowed_ptr = &t->cpus_allowed;
>
> In -RT we then can switch the cpus_ptr to
> t->cpus_allowed_ptr = &cpumask_of(task_cpu(p));
>
> in a migration disabled region. The rules are simple:
> - Code that 'uses' ->cpus_allowed would use the pointer.
> - Code that 'modifies' ->cpus_allowed would use the direct mask.
>
> I proposed this patch as a series earlier and it was shutdown due to the
> migrate_disable() bits. It has been said that migrate_disable() should
> only be used with RT and thus not introduced without it.
> I hereby propose only the mask CPU-bits.
>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> arch/ia64/kernel/mca.c | 2 +-
> arch/mips/include/asm/switch_to.h | 4 +--
> arch/mips/kernel/mips-mt-fpaff.c | 2 +-
> arch/mips/kernel/traps.c | 6 ++--
> arch/powerpc/platforms/cell/spufs/sched.c | 2 +-
> arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 2 +-
> drivers/infiniband/hw/hfi1/affinity.c | 6 ++--
> drivers/infiniband/hw/hfi1/sdma.c | 3 +-
> drivers/infiniband/hw/qib/qib_file_ops.c | 7 ++--
> fs/proc/array.c | 4 +--
> include/linux/sched.h | 5 +--
> init/init_task.c | 3 +-
> kernel/cgroup/cpuset.c | 2 +-
> kernel/fork.c | 2 ++
> kernel/sched/core.c | 40 +++++++++++-----------
> kernel/sched/cpudeadline.c | 4 +--
> kernel/sched/cpupri.c | 4 +--
> kernel/sched/deadline.c | 6 ++--
> kernel/sched/fair.c | 34 +++++++++---------
> kernel/sched/rt.c | 4 +--
> kernel/trace/trace_hwlat.c | 2 +-
> lib/smp_processor_id.c | 2 +-
> samples/trace_events/trace-events-sample.c | 2 +-
> 23 files changed, 75 insertions(+), 73 deletions(-)
Looks good to me in principle - Peter, Thomas, any fundamental
objections?
Thanks,
Ingo
next prev parent reply other threads:[~2019-05-02 15:11 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-23 14:26 [PATCH] sched: Provide a pointer to the valid CPU mask Sebastian Andrzej Siewior
2019-05-02 10:46 ` Sebastian Andrzej Siewior
2019-05-02 15:10 ` Ingo Molnar [this message]
2019-05-06 19:12 ` Thomas Gleixner
2019-05-08 9:47 ` Peter Zijlstra
2019-06-03 13:00 ` [tip:sched/core] sched/core: " tip-bot for Sebastian Andrzej Siewior
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=20190502151055.GA50195@gmail.com \
--to=mingo@kernel.org \
--cc=bigeasy@linutronix.de \
--cc=linux-kernel@vger.kernel.org \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
/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).