Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v4 2/4] sched/isolation: Extend nohz_full to isolate
 managed IRQs
To:     Peter Zijlstra <peterz@infradead.org>
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 <tglx@linutronix.de>
References: <20200928183529.471328-1-nitesh@redhat.com>
 <20200928183529.471328-3-nitesh@redhat.com>
 <20201023132505.GZ2628@hirez.programming.kicks-ass.net>
From:   Nitesh Narayan Lal <nitesh@redhat.com>
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: <ef8fbae8-06e1-b947-30b1-281afd330f01@redhat.com>
Date:   Fri, 23 Oct 2020 09:45:53 -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: <20201023132505.GZ2628@hirez.programming.kicks-ass.net>
Content-Type: multipart/signed; micalg=pgp-sha256;
 protocol="application/pgp-signature";
 boundary="HBIX5p6AJD4cCUtOGUhTn4euRVxpQy3ZZ"
Precedence: bulk

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 <frederic@kernel.org>
>> Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com>
>> ---
>>  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-----
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=evaw
-----END PGP SIGNATURE-----

--HBIX5p6AJD4cCUtOGUhTn4euRVxpQy3ZZ--