linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: Matthew Wilcox <willy@infradead.org>
To: Christopher Lameter <cl@linux.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] mm: introduce sysctl file to flush per-cpu vmstat statistics
Date: Tue, 17 Nov 2020 19:09:26 +0000	[thread overview]
Message-ID: <20201117190926.GU29991@casper.infradead.org> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2011171855500.215602@www.lameter.com>

On Tue, Nov 17, 2020 at 07:06:33PM +0000, Christopher Lameter wrote:
> On Tue, 17 Nov 2020, Matthew Wilcox wrote:
> 
> > On Tue, Nov 17, 2020 at 01:28:06PM -0300, Marcelo Tosatti wrote:
> > > For isolated applications that busy loop (packet processing with DPDK,
> > > for example), workqueue functions either stall (if the -rt app priority
> > > is higher than kworker thread priority) or interrupt the -rt app
> > > (if the -rt app priority is lower than kworker thread priority.
> >
> > This seems a bit obscure to expect an application to do.  Can we make
> > this happen automatically when we bind an rt task to a group of CPUs?
> 
> Well the way we used it was just to let things be and run in the busy
> loop. There could be another flush of the vmstat data and then the vmstat
> worker will disable itself. So two more workqueue executions before the
> processor completely dies down. But then we also need a period like
> that to trigger the NOHZ logic to switch off the timer. Right?
> 
> So what we would need would be something like a sysctl that puts the
> system into a quiet state by completing all workqueue items. Idle all
> subsystems that need it and put the cpu into NOHZ mode.

Why does it need to be something userspace does?  It would seem reasonable
that the kernel could figure out for itself that it's about to start
this CPU operating in isolated mode and flush all the work first?


  reply	other threads:[~2020-11-17 19:09 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-17 16:28 Marcelo Tosatti
2020-11-17 18:03 ` Matthew Wilcox
2020-11-17 19:06   ` Christopher Lameter
2020-11-17 19:09     ` Matthew Wilcox [this message]
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
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

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=20201117190926.GU29991@casper.infradead.org \
    --to=willy@infradead.org \
    --cc=akpm@linux-foundation.org \
    --cc=cl@linux.com \
    --cc=linux-mm@kvack.org \
    --cc=mtosatti@redhat.com \
    --subject='Re: [PATCH] mm: introduce sysctl file to flush per-cpu vmstat statistics' \
    /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

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox