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Mon, 5 Oct 2020 18:52:56 +0000 (UTC) Received: from [10.10.115.89] (ovpn-115-89.rdu2.redhat.com [10.10.115.89]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2609055767; Mon, 5 Oct 2020 18:52:52 +0000 (UTC) Subject: Re: [EXT] Re: [PATCH v4 03/13] task_isolation: userspace hard isolation from kernel To: Frederic Weisbecker , Alex Belits Cc: "mingo@kernel.org" , "davem@davemloft.net" , "linux-api@vger.kernel.org" , "rostedt@goodmis.org" , "peterz@infradead.org" , "linux-arch@vger.kernel.org" , "catalin.marinas@arm.com" , "tglx@linutronix.de" , "will@kernel.org" , Prasun Kapoor , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" References: <04be044c1bcd76b7438b7563edc35383417f12c8.camel@marvell.com> <20201001135640.GA1748@lothringen> <7e54b3c5e0d4c91eb64f2dd1583dd687bc34757e.camel@marvell.com> <20201004231404.GA66364@lothringen> 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: Mon, 5 Oct 2020 14:52:49 -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: <20201004231404.GA66364@lothringen> 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="FZsMq2mJZeIH5dAtjmHM1IGNAg59yNcN1" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --FZsMq2mJZeIH5dAtjmHM1IGNAg59yNcN1 Content-Type: multipart/mixed; boundary="iXkXMJXBMjNjUkrwCUh5aCwKUrA8HgQ0S" --iXkXMJXBMjNjUkrwCUh5aCwKUrA8HgQ0S Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US On 10/4/20 7:14 PM, Frederic Weisbecker wrote: > On Sun, Oct 04, 2020 at 02:44:39PM +0000, Alex Belits wrote: >> On Thu, 2020-10-01 at 15:56 +0200, Frederic Weisbecker wrote: >>> External Email >>> >>> ------------------------------------------------------------------- >>> --- >>> On Wed, Jul 22, 2020 at 02:49:49PM +0000, Alex Belits wrote: >>>> +/* >>>> + * Description of the last two tasks that ran isolated on a given >>>> CPU. >>>> + * This is intended only for messages about isolation breaking. We >>>> + * don't want any references to actual task while accessing this >>>> from >>>> + * CPU that caused isolation breaking -- we know nothing about >>>> timing >>>> + * and don't want to use locking or RCU. >>>> + */ >>>> +struct isol_task_desc { >>>> +=09atomic_t curr_index; >>>> +=09atomic_t curr_index_wr; >>>> +=09bool=09warned[2]; >>>> +=09pid_t=09pid[2]; >>>> +=09pid_t=09tgid[2]; >>>> +=09char=09comm[2][TASK_COMM_LEN]; >>>> +}; >>>> +static DEFINE_PER_CPU(struct isol_task_desc, isol_task_descs); >>> So that's quite a huge patch that would have needed to be split up. >>> Especially this tracing engine. >>> >>> Speaking of which, I agree with Thomas that it's unnecessary. It's >>> too much >>> code and complexity. We can use the existing trace events and perform >>> the >>> analysis from userspace to find the source of the disturbance. >> The idea behind this is that isolation breaking events are supposed to >> be known to the applications while applications run normally, and they >> should not require any analysis or human intervention to be handled. > Sure but you can use trace events for that. Just trace interrupts, workqu= eues, > timers, syscalls, exceptions and scheduler events and you get all the loc= al > disturbance. You might want to tune a few filters but that's pretty much = it. > > As for the source of the disturbances, if you really need that informatio= n, > you can trace the workqueue and timer queue events and just filter those = that > target your isolated CPUs. > I agree that we can do all those things with tracing. However, IMHO having a simplified logging mechanism to gather the source of violation may help in reducing the manual effort. Although, I am not sure how easy will it be to maintain such an interface over time. -- Thanks Nitesh --iXkXMJXBMjNjUkrwCUh5aCwKUrA8HgQ0S-- --FZsMq2mJZeIH5dAtjmHM1IGNAg59yNcN1 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEkXcoRVGaqvbHPuAGo4ZA3AYyozkFAl97a4EACgkQo4ZA3AYy oznBWxAAlhg9XOo89MStI92WCr4vACZOesnTMkmqmEwR20N1mxYpbpTGO8ewEJVv B/bFRU6fCizkzaD1BVGeRjwv5i/kNl7EcqbFgHquzdat8Lypn5mx93hJyGz1SYrr IKg8oH0AHD6dR3zeil/wxDe8xFDb29Bjz2B8ncGmvHrH4B7yvgLnKShsCYonv5Yu w2I6W9yROnImpJF2nYP9ZGyHyGcElrHB3367vAlPwH9lv6UhXZP2L5WplvEV5Zec pnLGYwlxMnbP1lW6gzEGnUF71fK7x3E3Q9eoFMqIZkmpfpmpjSlVW4Vd+Xu2hNeZ WYaHevr7hC/WxIwOR4o0uo322TgshcI86XHKyhrDH8sj9Zuy8brUt5zIwYdcZOZS 8+gkWKRbE21KmMQ/I9TZfmd1c/n1h56Z3d45KEkdrPZjP6pb1BG9DemgIrtNm1SI GTpjM6UBrTCGleWObLOJYbE/UDWbzLHPQmADUl45Zfti4T/2L4LZEBh0+qyAbEEk A28X9gY7D2eEx3w+sNbpWIX8dFPclAYliKMucM1nOv4MCcoF8K3dR8Wm8qFr7SnH GCNU/0IA4mUP+/h1C7eyBynRLPid5QGBmdlbFAYx36C9Qmr9GZJs3bbRAAKaUSW/ 6SJ6GfPHWpf7uhaieX4OHIvjLwlc3UPur/UWqqAPPYQxumSUxCg= =2AIi -----END PGP SIGNATURE----- --FZsMq2mJZeIH5dAtjmHM1IGNAg59yNcN1--