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Tue, 22 Sep 2020 13:55:13 +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 29AE827C21; Tue, 22 Sep 2020 13:55:00 +0000 (UTC) Subject: Re: [RFC][Patch v1 3/3] PCI: Limit pci_alloc_irq_vectors as per housekeeping CPUs From: Nitesh Narayan Lal To: Marcelo Tosatti , frederic@kernel.org, bhelgaas@google.com Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-pci@vger.kernel.org, sassmann@redhat.com, jeffrey.t.kirsher@intel.com, jacob.e.keller@intel.com, jlelli@redhat.com, hch@infradead.org, 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> <20200909150818.313699-4-nitesh@redhat.com> <20200910192208.GA24845@fuller.cnet> 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: <75a398cd-2050-e298-d718-eb56d4910133@redhat.com> Date: Tue, 22 Sep 2020 09:54:58 -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: X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 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="QUlCYZirVSnzLEka9GGa8MU8J8LhWkkvL" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --QUlCYZirVSnzLEka9GGa8MU8J8LhWkkvL Content-Type: multipart/mixed; boundary="FcDyyLvNvIuwxqbIsEYXJONQcvkR6PsHT" --FcDyyLvNvIuwxqbIsEYXJONQcvkR6PsHT Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US On 9/10/20 3:31 PM, Nitesh Narayan Lal wrote: > On 9/10/20 3:22 PM, Marcelo Tosatti wrote: >> On Wed, Sep 09, 2020 at 11:08:18AM -0400, Nitesh Narayan Lal wrote: >>> This patch limits the pci_alloc_irq_vectors max vectors that is passed = on >>> by the caller based on the available housekeeping CPUs by only using th= e >>> minimum of the two. >>> >>> A minimum of the max_vecs passed and available housekeeping CPUs is >>> derived to ensure that we don't create excess vectors which can be >>> problematic specifically in an RT environment. This is because for an R= T >>> environment unwanted IRQs are moved to the housekeeping CPUs from >>> isolated CPUs to keep the latency overhead to a minimum. If the number = of >>> housekeeping CPUs are significantly lower than that of the isolated CPU= s >>> we can run into failures while moving these IRQs to housekeeping due to >>> per CPU vector limit. >>> >>> Signed-off-by: Nitesh Narayan Lal >>> --- >>> include/linux/pci.h | 16 ++++++++++++++++ >>> 1 file changed, 16 insertions(+) >>> >>> diff --git a/include/linux/pci.h b/include/linux/pci.h >>> index 835530605c0d..750ba927d963 100644 >>> --- a/include/linux/pci.h >>> +++ b/include/linux/pci.h >>> @@ -38,6 +38,7 @@ >>> #include >>> #include >>> #include >>> +#include >>> #include >>> =20 >>> #include >>> @@ -1797,6 +1798,21 @@ static inline int >>> pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs, >>> =09=09 unsigned int max_vecs, unsigned int flags) >>> { >>> +=09unsigned int num_housekeeping =3D num_housekeeping_cpus(); >>> +=09unsigned int num_online =3D num_online_cpus(); >>> + >>> +=09/* >>> +=09 * Try to be conservative and at max only ask for the same number o= f >>> +=09 * vectors as there are housekeeping CPUs. However, skip any >>> +=09 * modification to the of max vectors in two conditions: >>> +=09 * 1. If the min_vecs requested are higher than that of the >>> +=09 * housekeeping CPUs as we don't want to prevent the initializat= ion >>> +=09 * of a device. >>> +=09 * 2. If there are no isolated CPUs as in this case the driver shou= ld >>> +=09 * already have taken online CPUs into consideration. >>> +=09 */ >>> +=09if (min_vecs < num_housekeeping && num_housekeeping !=3D num_online= ) >>> +=09=09max_vecs =3D min_t(int, max_vecs, num_housekeeping); >>> =09return pci_alloc_irq_vectors_affinity(dev, min_vecs, max_vecs, flag= s, >>> =09=09=09=09=09 NULL); >>> } >> If min_vecs > num_housekeeping, for example: >> >> /* PCI MSI/MSIx support */ >> #define XGBE_MSI_BASE_COUNT 4 >> #define XGBE_MSI_MIN_COUNT (XGBE_MSI_BASE_COUNT + 1) >> >> Then the protection fails. > Right, I was ignoring that case. > >> How about reducing max_vecs down to min_vecs, if min_vecs > >> num_housekeeping ? > Yes, I think this makes sense. > I will wait a bit to see if anyone else has any other comment and will po= st > the next version then. > Are there any other comments/concerns on this patch that I need to address = in the next posting? --=20 Nitesh --FcDyyLvNvIuwxqbIsEYXJONQcvkR6PsHT-- --QUlCYZirVSnzLEka9GGa8MU8J8LhWkkvL Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEkXcoRVGaqvbHPuAGo4ZA3AYyozkFAl9qAjIACgkQo4ZA3AYy ozk33w//QnSYbMCUx+8+VUAoHYDuyHaWIzzfcxjcrd9UXCQMI6hqcnoXfTx4yZxi daHkOR3jQPzlAZskWRCe1HHQsvkSFSJa8Ux1SbtB+JW1jSJgDWB6trt43GlrZN02 tyzNDfqYpFEwxdXzjYQcAp9eWuRzo0KDojWQ0FJyL2Rqgc7U4CNA2W0DsTx/lZUP UQMc4nbdBLwYd9RwZn/MKyrT3WCGgGnHLVx8nmUsvX5kH+jI9Z71csbN2kX3AhiF sVZuYY4Xmqf+hbFmbXynN0af/WijUrNWFh3KRpOtMVBtErPO5E6CN90kq3xOs5zT ngd4Zku2WydJptrZPprLPDMcyfQZjzbggfneW1+jTnI1r3PLiQMzUfG5AWo8YhZP HEPZ6J7bjqr+pfYzSUIB5WkuRO6S3nEIBLN0mpR62Ss3WUz73/HakQaFrKdulJR+ yFSF/5+CYxSzn8CNM2XWGPCgU9BFIiJy5koUsJYtjpsxcnSApxINtYK4Zsb43Xht V6ki3CY7ZNtaDVQGpdmWa/wqOuC/Sb4grdTCMMygp/Cv0RbNTCCN8n7XQcRwnfIP 1sSCnuqxKcAwvcXMOfRLCA9niM3cxfeBhauL+YzfkowM5GDvrHbZ/uqO0SMWy6cL zqrMEiblm5ycee1ajc0shb3SV8Uf/gIZv5hOMLtHHZSSXoXmV2o= =92yK -----END PGP SIGNATURE----- --QUlCYZirVSnzLEka9GGa8MU8J8LhWkkvL--