From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56C1FC43464 for ; Thu, 17 Sep 2020 22:09:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0D78F20878 for ; Thu, 17 Sep 2020 22:09:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="RTEWp4fA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726218AbgIQWJV (ORCPT ); Thu, 17 Sep 2020 18:09:21 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:28953 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725858AbgIQWJV (ORCPT ); Thu, 17 Sep 2020 18:09:21 -0400 X-Greylist: delayed 12341 seconds by postgrey-1.27 at vger.kernel.org; Thu, 17 Sep 2020 18:09:19 EDT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600380558; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=/6zFeSGPAG8xBPGsswa+zaFQxvJLetl2hxSyTaDI24g=; b=RTEWp4fAmop83NsWw9d0v/lqxy58jn572zwv/+93HeKL5c2fWLKNnxm1XVcK5ndL9YJASj RdOfQEsBnnK7LWEkGqxy7kPBFAWqachzaIgMXhJELnDX3awCWcX8B0EC27wHXJ0hXss81a nn6qmbWwxpCT692lGST5rqrOXZxByvM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-245-RM-hK7SZOwSS_3T8EivU9Q-1; Thu, 17 Sep 2020 18:09:16 -0400 X-MC-Unique: RM-hK7SZOwSS_3T8EivU9Q-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 19C9E10A7AE4; Thu, 17 Sep 2020 22:09:14 +0000 (UTC) Received: from [10.10.112.95] (ovpn-112-95.rdu2.redhat.com [10.10.112.95]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F416955761; Thu, 17 Sep 2020 22:09:05 +0000 (UTC) Subject: Re: [RFC][Patch v1 1/3] sched/isolation: API to get num of hosekeeping CPUs To: Bjorn Helgaas Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-pci@vger.kernel.org, frederic@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, Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot References: <20200917201123.GA1726926@bjorn-Precision-5520> 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: Thu, 17 Sep 2020 18:09:04 -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: <20200917201123.GA1726926@bjorn-Precision-5520> 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="qPHOouy6gPmk35aXRjjLdKpe2k9JahaLW" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --qPHOouy6gPmk35aXRjjLdKpe2k9JahaLW Content-Type: multipart/mixed; boundary="z470jYo3zBx5K3PjRdsFarqxC09qC8piH" --z470jYo3zBx5K3PjRdsFarqxC09qC8piH Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US On 9/17/20 4:11 PM, Bjorn Helgaas wrote: > [+cc Ingo, Peter, Juri, Vincent (scheduler maintainers)] > > s/hosekeeping/housekeeping/ (in subject) > > On Wed, Sep 09, 2020 at 11:08:16AM -0400, Nitesh Narayan Lal wrote: >> Introduce a new API num_housekeeping_cpus(), that can be used to retriev= e >> the number of housekeeping CPUs by reading an atomic variable >> __num_housekeeping_cpus. This variable is set from housekeeping_setup(). >> >> This API is introduced for the purpose of drivers that were previously >> relying only on num_online_cpus() to determine the number of MSIX vector= s >> to create. In an RT environment with large isolated but a fewer >> housekeeping CPUs this was leading to a situation where an attempt to >> move all of the vectors corresponding to isolated CPUs to housekeeping >> CPUs was failing due to per CPU vector limit. > Totally kibitzing here, but AFAICT the concepts of "isolated CPU" and > "housekeeping CPU" are not currently exposed to drivers, and it's not > completely clear to me that they should be. > > We have carefully constructed notions of possible, present, online, > active CPUs, and it seems like whatever we do here should be > somehow integrated with those. At one point I thought about tweaking num_online_cpus(), but then I quickly moved away from that just because it is extensively used in the kernel and = we don't have to modify the behavior at all those places. Thank you for including Peter and Vincent as well. I would be happy to discuss/explore other options. > >> If there are no isolated CPUs specified then the API returns the number >> of all online CPUs. >> >> Signed-off-by: Nitesh Narayan Lal >> --- >> include/linux/sched/isolation.h | 7 +++++++ >> kernel/sched/isolation.c | 23 +++++++++++++++++++++++ >> 2 files changed, 30 insertions(+) >> >> diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isola= tion.h >> index cc9f393e2a70..94c25d956d8a 100644 >> --- a/include/linux/sched/isolation.h >> +++ b/include/linux/sched/isolation.h >> @@ -25,6 +25,7 @@ extern bool housekeeping_enabled(enum hk_flags flags); >> extern void housekeeping_affine(struct task_struct *t, enum hk_flags fl= ags); >> extern bool housekeeping_test_cpu(int cpu, enum hk_flags flags); >> extern void __init housekeeping_init(void); >> +extern unsigned int num_housekeeping_cpus(void); >> =20 >> #else >> =20 >> @@ -46,6 +47,12 @@ static inline bool housekeeping_enabled(enum hk_flags= flags) >> static inline void housekeeping_affine(struct task_struct *t, >> =09=09=09=09 enum hk_flags flags) { } >> static inline void housekeeping_init(void) { } >> + >> +static unsigned int num_housekeeping_cpus(void) >> +{ >> +=09return num_online_cpus(); >> +} >> + >> #endif /* CONFIG_CPU_ISOLATION */ >> =20 >> static inline bool housekeeping_cpu(int cpu, enum hk_flags flags) >> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c >> index 5a6ea03f9882..7024298390b7 100644 >> --- a/kernel/sched/isolation.c >> +++ b/kernel/sched/isolation.c >> @@ -13,6 +13,7 @@ DEFINE_STATIC_KEY_FALSE(housekeeping_overridden); >> EXPORT_SYMBOL_GPL(housekeeping_overridden); >> static cpumask_var_t housekeeping_mask; >> static unsigned int housekeeping_flags; >> +static atomic_t __num_housekeeping_cpus __read_mostly; >> =20 >> bool housekeeping_enabled(enum hk_flags flags) >> { >> @@ -20,6 +21,27 @@ bool housekeeping_enabled(enum hk_flags flags) >> } >> EXPORT_SYMBOL_GPL(housekeeping_enabled); >> =20 >> +/* >> + * 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, enum= hk_flags flags) >> =20 >> =09housekeeping_flags |=3D flags; >> =20 >> +=09atomic_set(&__num_housekeeping_cpus, cpumask_weight(housekeeping_mas= k)); >> =09free_bootmem_cpumask_var(non_housekeeping_mask); >> =20 >> =09return 1; >> --=20 >> 2.27.0 >> --=20 Nitesh --z470jYo3zBx5K3PjRdsFarqxC09qC8piH-- --qPHOouy6gPmk35aXRjjLdKpe2k9JahaLW Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEkXcoRVGaqvbHPuAGo4ZA3AYyozkFAl9j3oAACgkQo4ZA3AYy ozkFzhAAre38UgoNY3QsPxENtstDExHNr59GinuBuAQFl/fQz3WTaG3p9BWrLXxB T1zP0C2xCWMS93UHReZWpRdkPSLqFMd35tmq6u5HyHBlvEUKMV6eX6By2LT7o52Z 2Uw2e21ZdQhXCj1WCq+3+OSvZvtlwr9oCSoAKibiKQUrVuofti43t5sJIaILxk4s 7pnzMiQZZJt2Ku6IaYpo5ydW9i2GEMLMmpSZt+9ZrS894GAp2NHPAzInp+yfyTRP iWG3ER4EzS6FTcRMuZ2Gt2dcToKP5ap4e95pGOx9Zk2aLlte6vfsEutww85GbWrK QaKWL9MEuYM3SSBt9NZ0Uo+6EptkK9w8WjRamW5FJPnaZ0TUDW0GAUXhV6PEb8+u htujjTvbWtQSsxgH3hkByUV7QB52IcobSvCKX1OOpuhiccBkRJ5HpykyDcj61kcK 04ZcoYzy20nLE36bHTSWjsblEbnAEEScY0OnMvJEn7MNC1UKdlSRM5mSckQDSmCA R7NFbxzzUFbGwltYDTEmq0Fs3M2nUptugn4qSU2A5k3mMh9QZdEi2cpH//tmA+hi 5a4OgzCQqvCoWM8s3fejSobgBn+QwUO20F2K2iskOp9vhXlleVDPYGpsVR8rr1Xg cFite/wdu8coI1wEKxQVr+l6+IQJN/3gP4vrQZYw42c5yELZGXA= =Ka3q -----END PGP SIGNATURE----- --qPHOouy6gPmk35aXRjjLdKpe2k9JahaLW--