From: Marcelo Tosatti <email@example.com> To: Christopher Lameter <firstname.lastname@example.org> Cc: Matthew Wilcox <email@example.com>, firstname.lastname@example.org, Andrew Morton <email@example.com> Subject: Re: [PATCH] mm: introduce sysctl file to flush per-cpu vmstat statistics Date: Tue, 17 Nov 2020 17:23:17 -0300 [thread overview] Message-ID: <20201117202317.GA282679@fuller.cnet> (raw) In-Reply-To: <alpine.DEB.firstname.lastname@example.org> 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? The application should not start its time sensitive loop until the workqueues have finished execution. > 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. Are you suggesting that instead of a specific file to control vmstat workqueue only, a more generic sysctl could be used? About NOHZ mode: the CPU should enter NOHZ automatically as soon as there is a single thread running, so unclear why that would be needed. Thanks.
next prev parent reply other threads:[~2020-11-17 20:23 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 2020-11-20 18:04 ` Christopher Lameter 2020-11-17 20:23 ` Marcelo Tosatti [this message] 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=20201117202317.GA282679@fuller.cnet \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.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