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Fri, 23 Oct 2020 13:46:07 +0000 (UTC) Received: from [10.10.113.74] (ovpn-113-74.rdu2.redhat.com [10.10.113.74]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A70276F7C4; Fri, 23 Oct 2020 13:45:54 +0000 (UTC) Subject: Re: [PATCH v4 2/4] sched/isolation: Extend nohz_full to isolate managed IRQs To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-pci@vger.kernel.org, intel-wired-lan@lists.osuosl.org, frederic@kernel.org, mtosatti@redhat.com, sassmann@redhat.com, jesse.brandeburg@intel.com, lihong.yang@intel.com, helgaas@kernel.org, jeffrey.t.kirsher@intel.com, jacob.e.keller@intel.com, jlelli@redhat.com, hch@infradead.org, bhelgaas@google.com, mike.marciniszyn@intel.com, dennis.dalessandro@intel.com, thomas.lendacky@amd.com, jiri@nvidia.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, lgoncalv@redhat.com, Thomas Gleixner References: <20200928183529.471328-1-nitesh@redhat.com> <20200928183529.471328-3-nitesh@redhat.com> <20201023132505.GZ2628@hirez.programming.kicks-ass.net> From: Nitesh Narayan Lal Autocrypt: addr=nitesh@redhat.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20201023132505.GZ2628@hirez.programming.kicks-ass.net> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=nitesh@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="HBIX5p6AJD4cCUtOGUhTn4euRVxpQy3ZZ" Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org Archived-At: List-Archive: List-Post: This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --HBIX5p6AJD4cCUtOGUhTn4euRVxpQy3ZZ Content-Type: multipart/mixed; boundary="wdjsMI8fejvw0TA72zPZM8sdeudoQSyk5" --wdjsMI8fejvw0TA72zPZM8sdeudoQSyk5 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US On 10/23/20 9:25 AM, Peter Zijlstra wrote: > On Mon, Sep 28, 2020 at 02:35:27PM -0400, Nitesh Narayan Lal wrote: >> Extend nohz_full feature set to include isolation from managed IRQS. Thi= s > So you say it's for managed-irqs, the feature is actually called > MANAGED_IRQ, but, AFAICT, it does *NOT* in fact affect managed IRQs. Ah my bad! I should replace the managed IRQS with MANAGED_IRQ. I can send another version with this fixed. > > Also, as per Thomas' earlier points, managed-irqs are in fact perfectly > fine and don't need help at at... Since the introduction of "genirq, sched/isolation: Isolate from handling managed interrupts" Within irq_do_set_affinity(), it is ensured that for managed intrrupts as well, the isolated CPUs are removed from the affinity mask. Hence, IMHO before this change managed interrupts were affecting the isolated CPUs. My intent of having this change is to basically allow isolation for nohz_full CPUs even when we don't have something like isolcpus. Does that make sense? > >> is required specifically for setups that only uses nohz_full and still >> requires isolation for maintaining lower latency for the listed CPUs. >> >> Suggested-by: Frederic Weisbecker >> Signed-off-by: Nitesh Narayan Lal >> --- >> kernel/sched/isolation.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c >> index 5a6ea03f9882..9df9598a9e39 100644 >> --- a/kernel/sched/isolation.c >> +++ b/kernel/sched/isolation.c >> @@ -141,7 +141,7 @@ static int __init housekeeping_nohz_full_setup(char = *str) >> =09unsigned int flags; >> =20 >> =09flags =3D HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU | >> -=09=09HK_FLAG_MISC | HK_FLAG_KTHREAD; >> +=09=09HK_FLAG_MISC | HK_FLAG_KTHREAD | HK_FLAG_MANAGED_IRQ; >> =20 >> =09return housekeeping_setup(str, flags); >> } >> --=20 >> 2.18.2 >> --=20 Nitesh --wdjsMI8fejvw0TA72zPZM8sdeudoQSyk5-- --HBIX5p6AJD4cCUtOGUhTn4euRVxpQy3ZZ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEkXcoRVGaqvbHPuAGo4ZA3AYyozkFAl+S3pEACgkQo4ZA3AYy ozmz/g/+NNlYNsGOBqRo+QTnk+ou/DfBVJmQBKlUzzd3Q2+duRldt2NPCXZfssJ9 ISHUMQNNGLlzrIl2D1IBR8Or3ng6s+Ou/pSfUA0xUIS6JRAySF2tFpG3boJmqBvL kbE3ty2oZnfox5pdJ/diJK5DmKAFsT9SDeDlgLhybiUbn+YQxcw/8FSw9xt9wRjL RBIt+9rctdaYdZBoP1xx9eFCh+gO6SBDvXoMARDOJ0kPmxhDAbjYo7lQzRdWK0g6 fXqzfRgK6kiwuh0LzJ95CzB1xh3Z4hiIQ/Q5N2JrB72sair3YaJMOnyeDIci8lCh p0YA95yjwS8fPDNRsWB6MMymrhhfZhvD9aVa3SjEBKgIHgg9QNnv+b0EAUDmLL5s yaqWePVxNS1vzq+/k4PgtTEBFlrxyxVzyTqOz7wDdYO9shTBt13C2sbCqjJGo5Rl utZXTYKN0vQTWxHoTlR0xgVAWrF+YmMYNAwkWKrybonmffemEEjJ8N2Slo4KJHr4 XLx2OnCOWI8qJIh0Dm4HK3ZrABWgDHBCMnCaGQBL3U6Hq6QtZ83IFd6sMwk56ykH 5ZXm7wFiiyIUNjjveWKJfEAV2ZheFrLh11CZfX7AwaRMeAbc45dVd/XB2CMAWCAB lgKtuvpwCEloPuRsPVPLtFgper6/El8FC0DYJoBNXh3BWvTM8vY= =evaw -----END PGP SIGNATURE----- --HBIX5p6AJD4cCUtOGUhTn4euRVxpQy3ZZ--