From: Bruce Richardson <bruce.richardson@intel.com>
To: Thomas Monjalon <thomas@monjalon.net>
Cc: "Morten Brørup" <mb@smartsharesystems.com>,
"Stephen Hemminger" <stephen@networkplumber.org>,
"Min Zhou" <zhoumin@loongson.cn>,
stable@dpdk.org, dev@dpdk.org,
"David Marchand" <david.marchand@redhat.com>,
"Anatoly Burakov" <anatoly.burakov@intel.com>,
"Narcisa Vasile" <navasile@linux.microsoft.com>,
"Tyler Retzlaff" <roretzla@linux.microsoft.com>,
"Dmitry Kozlyuk" <dmitry.kozliuk@gmail.com>,
"Konstantin Ananyev" <konstantin.v.ananyev@yandex.ru>,
"Andrew Rybchenko" <andrew.rybchenko@oktetlabs.ru>
Subject: Re: [PATCH] eal/unix: allow creating thread with real-time priority
Date: Wed, 25 Oct 2023 14:34:08 +0100 [thread overview]
Message-ID: <ZTkZUKMbLs06MY2N@bricha3-MOBL.ger.corp.intel.com> (raw)
In-Reply-To: <3767229.kQq0lBPeGt@thomas>
On Wed, Oct 25, 2023 at 03:15:49PM +0200, Thomas Monjalon wrote:
> 24/10/2023 18:04, Stephen Hemminger:
> > On Tue, 24 Oct 2023 15:55:13 +0200
> > Morten Brørup <mb@smartsharesystems.com> wrote:
> >
> > > >
> > > > 4. It MAY be used by preemptible multi-producer and/or preemptible multi-
> > > > consumer pthreads whose scheduling policy are all SCHED_OTHER(cfs), SCHED_IDLE
> > > > or SCHED_BATCH. User SHOULD be aware of the performance penalty before using
> > > > it.
> > > >
> > > > - 5. It MUST not be used by multi-producer/consumer pthreads, whose
> > > > scheduling policies are SCHED_FIFO or SCHED_RR.
> > > > + 5. It MUST not be used by multi-producer/consumer pthreads
> > > > + whose scheduling policies are ``SCHED_FIFO``
> > > > + or ``SCHED_RR`` (``RTE_THREAD_PRIORITY_REALTIME_CRITICAL``).
> > >
> > > Do the RTS or HTS ring modes make any difference here?
> > >
> > > Anyway, I agree that real-time priority should not be forbidden on Unix.
> > >
> > > Acked-by: Morten Brørup <mb@smartsharesystems.com>
> >
> > Please add a big warning message in the rte_thread.c and the documentation
> > to describe the problem. Need to have the "you have been warned" action.
>
> Yes I can add more warnings.
>
> > Use of RT priority is incompatible with 100% poll mode as is typically done
> > in DPDK applications. A real time thread has higher priority than other necessary
> > kernel threads on the same CPU. Therefore if the RT thread never sleeps, critical
> > system actions such as delayed writes, network packet processing and timer updates
> > will not happen which makes the system unstable.
>
> Yes, and it is shown by the test on loongarch:
> DPDK:fast-tests / threads_autotest TIMEOUT 80.01s
> http://mails.dpdk.org/archives/test-report/2023-October/488760.html
>
> I'll try to pass the test by adding a sleep in the test thread.
>
"sched_yield()" rather than sleep perhaps? Might better convey the
intention of the call.
next prev parent reply other threads:[~2023-10-25 13:34 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-24 12:54 Thomas Monjalon
2023-10-24 13:55 ` Morten Brørup
2023-10-24 16:04 ` Stephen Hemminger
2023-10-25 13:15 ` Thomas Monjalon
2023-10-25 13:34 ` Bruce Richardson [this message]
2023-10-25 13:44 ` Thomas Monjalon
2023-10-25 15:08 ` Stephen Hemminger
2023-10-25 15:14 ` Bruce Richardson
2023-10-25 15:18 ` Thomas Monjalon
2023-10-25 15:32 ` Thomas Monjalon
2023-10-25 15:13 ` [PATCH v2] " Thomas Monjalon
2023-10-25 15:37 ` Stephen Hemminger
2023-10-25 16:46 ` Thomas Monjalon
2023-10-25 17:54 ` Morten Brørup
2023-10-25 21:33 ` Stephen Hemminger
2023-10-26 7:33 ` Morten Brørup
2023-10-26 16:32 ` Stephen Hemminger
2023-10-26 17:07 ` Morten Brørup
2023-10-26 0:00 ` Stephen Hemminger
[not found] ` <20231025163352.1076755-1-thomas@monjalon.net>
2023-10-25 16:31 ` [PATCH v3 2/2] " Thomas Monjalon
[not found] ` <20231026134313.1165954-1-thomas@monjalon.net>
2023-10-26 13:37 ` [PATCH v4 " Thomas Monjalon
[not found] ` <20231026142749.1174372-1-thomas@monjalon.net>
2023-10-26 14:19 ` [PATCH v5 " Thomas Monjalon
2023-10-27 8:08 ` [PATCH v6 1/1] " Thomas Monjalon
2023-10-27 8:45 ` Morten Brørup
2023-10-27 9:11 ` Thomas Monjalon
2023-10-27 18:15 ` Stephen Hemminger
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