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Tue, 22 Sep 2020 13:50:59 +0000 (UTC) Received: from [10.10.115.78] (ovpn-115-78.rdu2.redhat.com [10.10.115.78]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AF02E3782; Tue, 22 Sep 2020 13:50:56 +0000 (UTC) Subject: Re: [RFC][Patch v1 1/3] sched/isolation: API to get num of hosekeeping CPUs To: Frederic Weisbecker Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-pci@vger.kernel.org, mtosatti@redhat.com, sassmann@redhat.com, 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, jerinj@marvell.com, mathias.nyman@intel.com, jiri@nvidia.com References: <20200909150818.313699-1-nitesh@redhat.com> <20200909150818.313699-2-nitesh@redhat.com> <20200921234044.GA31047@lenoir> <20200922100817.GB5217@lenoir> From: Nitesh Narayan Lal Autocrypt: addr=nitesh@redhat.com; prefer-encrypt=mutual; keydata= mQINBFl4pQoBEADT/nXR2JOfsCjDgYmE2qonSGjkM1g8S6p9UWD+bf7YEAYYYzZsLtbilFTe z4nL4AV6VJmC7dBIlTi3Mj2eymD/2dkKP6UXlliWkq67feVg1KG+4UIp89lFW7v5Y8Muw3Fm uQbFvxyhN8n3tmhRe+ScWsndSBDxYOZgkbCSIfNPdZrHcnOLfA7xMJZeRCjqUpwhIjxQdFA7 n0s0KZ2cHIsemtBM8b2WXSQG9CjqAJHVkDhrBWKThDRF7k80oiJdEQlTEiVhaEDURXq+2XmG jpCnvRQDb28EJSsQlNEAzwzHMeplddfB0vCg9fRk/kOBMDBtGsTvNT9OYUZD+7jaf0gvBvBB lbKmmMMX7uJB+ejY7bnw6ePNrVPErWyfHzR5WYrIFUtgoR3LigKnw5apzc7UIV9G8uiIcZEn C+QJCK43jgnkPcSmwVPztcrkbC84g1K5v2Dxh9amXKLBA1/i+CAY8JWMTepsFohIFMXNLj+B RJoOcR4HGYXZ6CAJa3Glu3mCmYqHTOKwezJTAvmsCLd3W7WxOGF8BbBjVaPjcZfavOvkin0u DaFvhAmrzN6lL0msY17JCZo046z8oAqkyvEflFbC0S1R/POzehKrzQ1RFRD3/YzzlhmIowkM BpTqNBeHEzQAlIhQuyu1ugmQtfsYYq6FPmWMRfFPes/4JUU/PQARAQABtCVOaXRlc2ggTmFy YXlhbiBMYWwgPG5pbGFsQHJlZGhhdC5jb20+iQI9BBMBCAAnBQJZeKUKAhsjBQkJZgGABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheAAAoJEKOGQNwGMqM56lEP/A2KMs/pu0URcVk/kqVwcBhU SnvB8DP3lDWDnmVrAkFEOnPX7GTbactQ41wF/xwjwmEmTzLrMRZpkqz2y9mV0hWHjqoXbOCS 6RwK3ri5e2ThIPoGxFLt6TrMHgCRwm8YuOSJ97o+uohCTN8pmQ86KMUrDNwMqRkeTRW9wWIQ EdDqW44VwelnyPwcmWHBNNb1Kd8j3xKlHtnS45vc6WuoKxYRBTQOwI/5uFpDZtZ1a5kq9Ak/ MOPDDZpd84rqd+IvgMw5z4a5QlkvOTpScD21G3gjmtTEtyfahltyDK/5i8IaQC3YiXJCrqxE r7/4JMZeOYiKpE9iZMtS90t4wBgbVTqAGH1nE/ifZVAUcCtycD0f3egX9CHe45Ad4fsF3edQ ESa5tZAogiA4Hc/yQpnnf43a3aQ67XPOJXxS0Qptzu4vfF9h7kTKYWSrVesOU3QKYbjEAf95 NewF9FhAlYqYrwIwnuAZ8TdXVDYt7Z3z506//sf6zoRwYIDA8RDqFGRuPMXUsoUnf/KKPrtR ceLcSUP/JCNiYbf1/QtW8S6Ca/4qJFXQHp0knqJPGmwuFHsarSdpvZQ9qpxD3FnuPyo64S2N Dfq8TAeifNp2pAmPY2PAHQ3nOmKgMG8Gn5QiORvMUGzSz8Lo31LW58NdBKbh6bci5+t/HE0H pnyVf5xhNC/FuQINBFl4pQoBEACr+MgxWHUP76oNNYjRiNDhaIVtnPRqxiZ9v4H5FPxJy9UD Bqr54rifr1E+K+yYNPt/Po43vVL2cAyfyI/LVLlhiY4yH6T1n+Di/hSkkviCaf13gczuvgz4 KVYLwojU8+naJUsiCJw01MjO3pg9GQ+47HgsnRjCdNmmHiUQqksMIfd8k3reO9SUNlEmDDNB XuSzkHjE5y/R/6p8uXaVpiKPfHoULjNRWaFc3d2JGmxJpBdpYnajoz61m7XJlgwl/B5Ql/6B dHGaX3VHxOZsfRfugwYF9CkrPbyO5PK7yJ5vaiWre7aQ9bmCtXAomvF1q3/qRwZp77k6i9R3 tWfXjZDOQokw0u6d6DYJ0Vkfcwheg2i/Mf/epQl7Pf846G3PgSnyVK6cRwerBl5a68w7xqVU 4KgAh0DePjtDcbcXsKRT9D63cfyfrNE+ea4i0SVik6+N4nAj1HbzWHTk2KIxTsJXypibOKFX 2VykltxutR1sUfZBYMkfU4PogE7NjVEU7KtuCOSAkYzIWrZNEQrxYkxHLJsWruhSYNRsqVBy KvY6JAsq/i5yhVd5JKKU8wIOgSwC9P6mXYRgwPyfg15GZpnw+Fpey4bCDkT5fMOaCcS+vSU1 UaFmC4Ogzpe2BW2DOaPU5Ik99zUFNn6cRmOOXArrryjFlLT5oSOe4IposgWzdwARAQABiQIl BBgBCAAPBQJZeKUKAhsMBQkJZgGAAAoJEKOGQNwGMqM5ELoP/jj9d9gF1Al4+9bngUlYohYu 0sxyZo9IZ7Yb7cHuJzOMqfgoP4tydP4QCuyd9Q2OHHL5AL4VFNb8SvqAxxYSPuDJTI3JZwI7 d8JTPKwpulMSUaJE8ZH9n8A/+sdC3CAD4QafVBcCcbFe1jifHmQRdDrvHV9Es14QVAOTZhnJ vweENyHEIxkpLsyUUDuVypIo6y/Cws+EBCWt27BJi9GH/EOTB0wb+2ghCs/i3h8a+bi+bS7L FCCm/AxIqxRurh2UySn0P/2+2eZvneJ1/uTgfxnjeSlwQJ1BWzMAdAHQO1/lnbyZgEZEtUZJ x9d9ASekTtJjBMKJXAw7GbB2dAA/QmbA+Q+Xuamzm/1imigz6L6sOt2n/X/SSc33w8RJUyor SvAIoG/zU2Y76pKTgbpQqMDmkmNYFMLcAukpvC4ki3Sf086TdMgkjqtnpTkEElMSFJC8npXv 3QnGGOIfFug/qs8z03DLPBz9VYS26jiiN7QIJVpeeEdN/LKnaz5LO+h5kNAyj44qdF2T2AiF HxnZnxO5JNP5uISQH3FjxxGxJkdJ8jKzZV7aT37sC+Rp0o3KNc+GXTR+GSVq87Xfuhx0LRST NK9ZhT0+qkiN7npFLtNtbzwqaqceq3XhafmCiw8xrtzCnlB/C4SiBr/93Ip4kihXJ0EuHSLn VujM7c/b4pps Organization: Red Hat Inc, Message-ID: Date: Tue, 22 Sep 2020 09:50:55 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200922100817.GB5217@lenoir> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 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="6rGvnlUKxR9RsDui3Gutxxh1oToVXjqL0" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --6rGvnlUKxR9RsDui3Gutxxh1oToVXjqL0 Content-Type: multipart/mixed; boundary="cwBsE0kL1GlZot94IXd2XWzTp29pWSk4k" --cwBsE0kL1GlZot94IXd2XWzTp29pWSk4k Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US On 9/22/20 6:08 AM, Frederic Weisbecker wrote: > On Mon, Sep 21, 2020 at 11:16:51PM -0400, Nitesh Narayan Lal wrote: >> On 9/21/20 7:40 PM, Frederic Weisbecker wrote: >>> On Wed, Sep 09, 2020 at 11:08:16AM -0400, Nitesh Narayan Lal wrote: >>>> +/* >>>> + * num_housekeeping_cpus() - Read the number of housekeeping CPUs. >>>> + * >>>> + * This function returns the number of available housekeeping CPUs >>>> + * based on __num_housekeeping_cpus which is of type atomic_t >>>> + * and is initialized at the time of the housekeeping setup. >>>> + */ >>>> +unsigned int num_housekeeping_cpus(void) >>>> +{ >>>> +=09unsigned int cpus; >>>> + >>>> +=09if (static_branch_unlikely(&housekeeping_overridden)) { >>>> +=09=09cpus =3D atomic_read(&__num_housekeeping_cpus); >>>> +=09=09/* We should always have at least one housekeeping CPU */ >>>> +=09=09BUG_ON(!cpus); >>>> +=09=09return cpus; >>>> +=09} >>>> +=09return num_online_cpus(); >>>> +} >>>> +EXPORT_SYMBOL_GPL(num_housekeeping_cpus); >>>> + >>>> int housekeeping_any_cpu(enum hk_flags flags) >>>> { >>>> =09int cpu; >>>> @@ -131,6 +153,7 @@ static int __init housekeeping_setup(char *str, en= um hk_flags flags) >>>> =20 >>>> =09housekeeping_flags |=3D flags; >>>> =20 >>>> +=09atomic_set(&__num_housekeeping_cpus, cpumask_weight(housekeeping_m= ask)); >>> So the problem here is that it takes the whole cpumask weight but you'r= e only >>> interested in the housekeepers who take the managed irq duties I guess >>> (HK_FLAG_MANAGED_IRQ ?). >> IMHO we should also consider the cases where we only have nohz_full. >> Otherwise, we may run into the same situation on those setups, do you ag= ree? > I guess it's up to the user to gather the tick and managed irq housekeepi= ng > together? TBH I don't have a very strong case here at the moment. But still, IMHO, this will force the user to have both managed irqs and nohz_full in their environments to avoid these kinds of issues. Is that how we would like to proceed? The reason why I want to get this clarity is that going forward for any RT related work I can form my thoughts based on this discussion. > > Of course that makes the implementation more complicated. But if this is > called only on drivers initialization for now, this could be just a funct= ion > that does: > > cpumask_weight(cpu_online_mask | housekeeping_cpumask(HK_FLAG_MANAGED_IRQ= )) Ack, this makes more sense. > > And then can we rename it to housekeeping_num_online()? It could be just me, but does something like hk_num_online_cpus() makes mor= e sense here? > > Thanks. > >>>> =09free_bootmem_cpumask_var(non_housekeeping_mask); >>>> =20 >>>> =09return 1; >>>> --=20 >>>> 2.27.0 >>>> >> --=20 >> Thanks >> Nitesh >> > > --=20 Thanks Nitesh --cwBsE0kL1GlZot94IXd2XWzTp29pWSk4k-- --6rGvnlUKxR9RsDui3Gutxxh1oToVXjqL0 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEkXcoRVGaqvbHPuAGo4ZA3AYyozkFAl9qAT8ACgkQo4ZA3AYy ozmBpw/9EKYTu09viJpapk2luJCLxDL/fV+jsf56t32jq2vM01Q3edO7ffPwEB+l GvqpJPgK2KyJgoxYLp4SmYdgRNhJ99RbhL0If6mbXBUV+l34wtGYBvgwFklq6Qjr 8C3QGShrEHLagiDkt3v89dpJDfTNvTyxFS4ftE4xtL9Cgw8Y8jJzezrFsSPtXTTl ZOEZYJb67GU+LECYI0SIxSiiW/qvvKnq4HkYJJ0/uDGSSXbfCPqwW+OMQGXN2ZUl oM/khLmpkwSgEc/bNul2nIf2pBclXa4nucC50jj8nVAMrPVvJMqdE4DHlCib06PW T303KvFtGTfZzfF0wNMeZXPFwSmB9jBuAxr3it0cLLB4+hHVD4FGX/ehegmvzXf3 sgpeWpKUVp18gmQgj4BEzdmCkVGDRvuQnLyffcDESzREUuWuMjsMrLfuPHdbwra7 rQcs5BGbC7ARlo4/i6RgEcTkrZjTXCO0z7y19Wuwh8LpQVHJHk6iY8d9LmeHnQlX HtOp/akiwPCsf4stfEXp0y/lFukHxfdTY6z9qi5rxUjtwDmf/lkDCWwQr5RDYWbZ 4WrlUaOc0KYDJIXdj7s6WbguRkQY6yw7iMwt74zNqqwGS00Nhio75FIz82KDHdVX 33nzVPF/S2TrKodGzQGiD7A8eG9pykApaC/A+5xAp/OJC2gDLNw= =C3Gd -----END PGP SIGNATURE----- --6rGvnlUKxR9RsDui3Gutxxh1oToVXjqL0--