From: Christoph Lameter <cl@linux.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Alex Belits <abelits@marvell.com>, Phil Auld <pauld@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Frederic Weisbecker <frederic@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] mm: introduce sysctl file to flush per-cpu vmstat statistics
Date: Mon, 30 Nov 2020 09:31:47 +0000 (UTC) [thread overview]
Message-ID: <alpine.DEB.2.22.394.2011300927120.337729@www.lameter.com> (raw)
In-Reply-To: <20201127154845.GA9100@fuller.cnet>
On Fri, 27 Nov 2020, Marcelo Tosatti wrote:
> Decided to switch to prctl interface, and then it starts
> to become similar to "task mode isolation" patchset API.
Right I think that was a good approach.
> In addition to quiescing pending activities on the CPU, it would
> also be useful to assign a per-task attribute (which is then assigned
> to a per-CPU attribute), indicating whether that CPU is running
> an isolated task or not.
Sounds good but what would this do? Give a warning like the isolation
patchset?
> This per-CPU attribute can be used to, for example, return -EBUSY
> from ring_buffer_resize() (or any other IPI generating activity
> which can return an error to userspace).
Yes good.
> So rather than:
>
> prctl(PR_QUIESCE_CPU) (current interface, similar to
> initial message on the thread but with prctl rather than
> sysfs)
>
> To be called before real time loop, one would have:
>
> prctl(PR_SET_TASK_ISOLATION, ISOLATION_ENABLE) [1]
> real time loop
> prctl(PR_SET_TASK_ISOLATION, ISOLATION_DISABLE)
>
> (with the attribute also being cleared on task exit).
>
> The general description would be:
>
> "Set task isolated mode for a given task, returning an error
> if the task is not pinned to a single CPU.
>
> In this mode, the kernel will avoid interruptions to isolated
> CPUs when possible."
>
> Any objections against such an interface ?
Maybe do both like in the isolation patchset?
Often code can tolerate a few interruptions (in some code branches
regular syscalls may be needed) but one wants the thread to be
as quiet as possible.
next prev parent reply other threads:[~2020-11-30 9:32 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-17 16:28 [PATCH] mm: introduce sysctl file to flush per-cpu vmstat statistics Marcelo Tosatti
2020-11-17 18:03 ` Matthew Wilcox
2020-11-17 19:06 ` Christopher Lameter
2020-11-17 19:09 ` Matthew Wilcox
2020-11-20 18:04 ` Christopher Lameter
2020-11-17 20:23 ` Marcelo Tosatti
2020-11-20 18:02 ` Marcelo Tosatti
2020-11-20 18:20 ` Christopher Lameter
2020-11-23 18:02 ` Marcelo Tosatti
2020-11-24 17:12 ` Vlastimil Babka
2020-11-24 19:52 ` Marcelo Tosatti
2020-11-27 15:48 ` Marcelo Tosatti
2020-11-28 3:49 ` [EXT] " Alex Belits
2020-11-30 18:18 ` Marcelo Tosatti
2020-11-30 18:29 ` Marcelo Tosatti
2020-12-03 22:47 ` Alex Belits
2020-12-03 22:21 ` Alex Belits
2020-11-30 9:31 ` Christoph Lameter [this message]
2020-12-02 12:43 ` Marcelo Tosatti
2020-12-02 15:57 ` Thomas Gleixner
2020-12-02 17:43 ` Christoph Lameter
2020-12-03 3:17 ` Thomas Gleixner
2020-12-07 8:08 ` Christoph Lameter
2020-12-07 16:09 ` Thomas Gleixner
2020-12-07 19:01 ` Thomas Gleixner
2020-12-02 18:38 ` Marcelo Tosatti
2020-12-04 0:20 ` Frederic Weisbecker
2020-12-04 13:31 ` Marcelo Tosatti
2020-12-04 1:43 ` [EXT] " Alex Belits
2021-01-13 12:15 ` [RFC] tentative prctl task isolation interface Marcelo Tosatti
2021-01-14 9:22 ` Christoph Lameter
2021-01-14 19:34 ` Marcelo Tosatti
2021-01-15 13:24 ` Christoph Lameter
2021-01-15 18:35 ` Alex Belits
2021-01-21 15:51 ` Marcelo Tosatti
2021-01-21 16:20 ` Marcelo Tosatti
2021-01-22 13:05 ` Marcelo Tosatti
2021-02-01 10:48 ` Christoph Lameter
2021-02-01 12:47 ` Alex Belits
2021-02-01 18:20 ` Marcelo Tosatti
2021-01-18 15:18 ` Marcelo Tosatti
2020-11-24 5:02 ` [mm] e655d17ffa: BUG:using_smp_processor_id()in_preemptible kernel test robot
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