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Wed, 25 Oct 2023 09:44:27 -0400 (EDT) From: Thomas Monjalon <thomas@monjalon.net> To: Bruce Richardson <bruce.richardson@intel.com>, Tyler Retzlaff <roretzla@linux.microsoft.com> Cc: dev@dpdk.org, Morten =?ISO-8859-1?Q?Br=F8rup?= <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 15:44:25 +0200 Message-ID: <3187925.5fSG56mABF@thomas> In-Reply-To: <ZTkZUKMbLs06MY2N@bricha3-MOBL.ger.corp.intel.com> References: <20231024125416.798897-1-thomas@monjalon.net> <3767229.kQq0lBPeGt@thomas> <ZTkZUKMbLs06MY2N@bricha3-MOBL.ger.corp.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" X-BeenThere: stable@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: patches for DPDK stable branches <stable.dpdk.org> List-Unsubscribe: <https://mails.dpdk.org/options/stable>, <mailto:stable-request@dpdk.org?subject=unsubscribe> List-Archive: <http://mails.dpdk.org/archives/stable/> List-Post: <mailto:stable@dpdk.org> List-Help: <mailto:stable-request@dpdk.org?subject=help> List-Subscribe: <https://mails.dpdk.org/listinfo/stable>, <mailto:stable-request@dpdk.org?subject=subscribe> Errors-To: stable-bounces@dpdk.org 25/10/2023 15:34, Bruce Richardson: > 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 Br=F8rup <mb@smartsharesystems.com> wrote: > > >=20 > > > > >=20 > > > > > 4. It MAY be used by preemptible multi-producer and/or preempt= ible multi- > > > > > consumer pthreads whose scheduling policy are all SCHED_OTHER(cfs= ), SCHED_IDLE > > > > > or SCHED_BATCH. User SHOULD be aware of the performance penalty b= efore using > > > > > it. > > > > >=20 > > > > > - 5. It MUST not be used by multi-producer/consumer pthreads, wh= ose > > > > > 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``)= =2E =20 > > > >=20 > > > > Do the RTS or HTS ring modes make any difference here? > > > >=20 > > > > Anyway, I agree that real-time priority should not be forbidden on = Unix. > > > >=20 > > > > Acked-by: Morten Br=F8rup <mb@smartsharesystems.com> > > >=20 > > > Please add a big warning message in the rte_thread.c and the document= ation > > > to describe the problem. Need to have the "you have been warned" acti= on. > >=20 > > Yes I can add more warnings. > >=20 > > > Use of RT priority is incompatible with 100% poll mode as is typicall= y done > > > in DPDK applications. A real time thread has higher priority than oth= er necessary > > > kernel threads on the same CPU. Therefore if the RT thread never slee= ps, critical > > > system actions such as delayed writes, network packet processing and = timer updates > > > will not happen which makes the system unstable. > >=20 > > 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 > >=20 > > I'll try to pass the test by adding a sleep in the test thread. > >=20 >=20 > "sched_yield()" rather than sleep perhaps? Might better convey the > intention of the call. Do we have sched_yield on Windows?