From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 49B981BDDC for ; Mon, 2 Oct 2023 15:20:25 +0000 (UTC) Received: from mout.gmx.net (mout.gmx.net [212.227.17.22]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8B543DD for ; Mon, 2 Oct 2023 08:20:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.de; s=s31663417; t=1696260008; x=1696864808; i=efault@gmx.de; bh=WvFv/02aIRQRfW/WN5YGX90t8mwO4vULzSd8xWRLid8=; h=X-UI-Sender-Class:Subject:From:To:Cc:Date:In-Reply-To:References; b=PA8/IpoeObhhr80fE8e6WmdChHKyPHP2CMu0ADhS7+kdZsPcgPDmyGh1vkwKHXd4WQT90XHQ2iK gf4inMZiC8GfPMSWTf59SZ5ayOOwEEwOK701wURDB7hp7hE84tMJyi0CnK5xBrwX8CZJO0qaq6bu6 ht+TPHnOas1GtAROAG6gi+hJDFheAhQAhtuQuwsR13s0eLsWkvZmJXCtRDSwdygsLeX3XROTe3A/k KtQFnlOPiBjSThuqVL1tV7g4qBUJp5NH4uY6shHIEPkLG6qslqjcLOL63NicVAwFIbZG5nqCjvbNb XA6VUqC/OuzH/C7kuIA3eYhfFZe56KRgf3wA== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from homer.fritz.box ([212.114.172.11]) by mail.gmx.net (mrgmx105 [212.227.17.168]) with ESMTPSA (Nemesis) id 1MfYPY-1rFleC27dQ-00fwNs; Mon, 02 Oct 2023 17:20:08 +0200 Message-ID: Subject: Re: High latency of a system based on 5.19 rt From: Mike Galbraith To: Sebastian Andrzej Siewior Cc: Clark Williams , "g.medini" , RT Date: Mon, 02 Oct 2023 17:20:07 +0200 In-Reply-To: <20231002141611.f1H8qyiR@linutronix.de> References: <8eb75f2118086edf828ac059999fd52b64382576.camel@gmx.de> <20231002100542.59fbxJ0f@linutronix.de> <8586b9812dccc6248e0518efaf973c4467324b70.camel@gmx.de> <20231002141611.f1H8qyiR@linutronix.de> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.4 Precedence: bulk X-Mailing-List: linux-rt-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:Y2BcSNpx8PQGt7/6QEDPvI017oAnxhNqfp/0pgqChWv8MR9RnI9 CklnvW4n2VQYFyUw8rWxGlvAwNE3+UoWLk6TeQg+AI6PoF32INUzx7mEcOidyDOZWbr5r0+ CBxTEacZ2fwYKA4S9c5BHJXlOM97iSM0Pv+Xjgu7sl4KepTtcbLOS9NbIQ8QYGoJD6nv/yg 6rE55gdxX3hbgKitYe0TA== UI-OutboundReport: notjunk:1;M01:P0:p5mzxco8UAk=;YF5d0UC8XH1vHHDIqHEF92AU4CS mvX3X6zODjxe2LXSvnMTaxYZNveYnnKQrKF0ca9aTtf/KJbjrKLSfgDR4DaEX+vQ+ttowM4g5 v2/vLyf0PmTb3vuoZW0u/dquF0snE/OMXdesmot+yCl6Y6iRLdj/VFk0eFHHdFyfqCB39Ij9U GqoTVzowarF6VTjAfb4F64vob5hBhBKraf8PtQqnxT9+cVxTbojddtZA3E8XGvvRNW2vbTSF4 ceUxgUBCbwg58tVCBwewErXMMN1QPUBXjeLbJFQ1nlHq5uTv3/CnY0zCq/Gi2mwTHWDqcRGjb Kit1WGYEXpCS24mZBHFnMOSjmqpFeqfS13G+ShBhmgsHCADChLoaVEqWZnMvmjq1nv5pbv5te DPQ8fGIS+r25TH1foKQ6OwS+efCkYImqQATGiYGYAZxxvh9uBIec1cBgvBd0xklz5YGckGeXY +Y5TBAOAVjnV2UBZ9rIJOme8Dtkt3DRt9w2tkbp9y4qZ+g1j618073sVdLuvrSsWbNnEXlplv Hkr+S3d3lmeXpUtj16yPJuUtp8R1gkSqfCcWrhYBmjj5fEZU5PRaozLMmmym+yWhZpojUasoT GoacQf0kBcrkaNydKxeAcUV0Zzy/dlTOcyUwmmKP7l86duz9PVg3jdN28HKYAKjboy9/XNzFG aWFZv99iXowipOdv5E+YDoerQCsj+GvY24t9PErNKRYDa1GawuFyhh98Fta7SrBw5vo6PbDRi tVJlilhcQN47iYcYwEKD9V0yEMsLBTigbxD2XGrIPn2kfyZZiZm6w/JMdtRavu7Ucn/lteEYI AgNhrH9c4q7WXYksMTk7Yqci3ToJbN3vYBYahO6UIls9nLhNJh2v8WPpUxZLufH+C97v9ABjU wchtisa0oZKeamRsgA2V4ckvGiYsQam63LRhuCXcm1F49XTUw9czs0UDarUqhe9eYa3V2S9ng Oh40vA== X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_BLOCKED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On Mon, 2023-10-02 at 16:16 +0200, Sebastian Andrzej Siewior wrote: > On 2023-10-02 13:58:57 [+0200], Mike Galbraith wrote: > > > Why not perform all wakes from hardirq then? > > > > Sounds good to me iff we're talking about a dinky irq width delta. > > > > Threads bundling up what are otherwise irq context cycles is loaded > > with goodness, but static priority leaves you holding a bill and payin= g > > context switch fees on top.=C2=A0 Pick your poison carefully applies I > > suppose.=C2=A0 A tiny swig of hemlock can't do _too_ much harm, right = ;-) > > A swarm of wake-ups for SCHED_OTHER at prio 50+ will delay your threaded > interrupt handler and everything else that runs 50 and lower. > Since SCHED_OTHER is less important than any RT task, the delay is > usually of lower concern. Sure, but you also have to weigh when to stop caring about inversion.=C2= =A0 I'd personally prefer an ever so slightly wider IRQ, but yeah, there is no free lunch, it's a trade. (wrt SCHED_OTHER wakeup swarm, in an environment where it's a concern, those perturbations are likely the least of your perturbation worries) -Mike