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Fri, 11 Jun 2021 16:49:55 +0000 From: Krishna Reddy To: Sai Prakash Ranjan CC: Robin Murphy , "linux-arm-msm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "iommu@lists.linux-foundation.org" , Will Deacon , "linux-arm-kernel@lists.infradead.org" , Thierry Reding Subject: RE: [PATCH] iommu/io-pgtable-arm: Optimize partial walk flush for large scatter-gather list Thread-Topic: [PATCH] iommu/io-pgtable-arm: Optimize partial walk flush for large scatter-gather list Thread-Index: AQHXXT84btg0466hEE2rkvq94oyuZasMBHAAgACy+QCAAD6WAIAAB6mAgAAg2ACAAAWcgIAAPESAgACQdxCAAA05AIABAqfQ Date: Fri, 11 Jun 2021 16:49:54 +0000 Message-ID: References: <20210609145315.25750-1-saiprakash.ranjan@codeaurora.org> <35bfd245-45e2-8083-b620-330d6dbd7bd7@arm.com> <12067ffb8243b220cf03e83aaac3e823@codeaurora.org> <266f190e-99ae-9175-cf13-7a77730af389@arm.com> <61c69d23-324a-85d7-2458-dfff8df9280b@arm.com> <07001b4ed6c0a491eacce6e4dc13ab5e@codeaurora.org> In-Reply-To: <07001b4ed6c0a491eacce6e4dc13ab5e@codeaurora.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: codeaurora.org; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: BY5PR12MB3764.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 1e148353-9cbe-4fa9-1b21-08d92cf8f0da X-MS-Exchange-CrossTenant-originalarrivaltime: 11 Jun 2021 16:49:55.2144 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: OKRDVM9JdY620BWzdf2TshCKxIJT7Jy2rlcOfar5qJXfRWIqeYk6XiTTc3bfOCerWPx2yoBw9RVqmiMiJDxQtw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR12MB4744 Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org Hi Sai, > >> > No, the unmap latency is not just in some test case written, the > >> > issue is very real and we have workloads where camera is reporting > >> > frame drops because of this unmap latency in the order of 100s of > milliseconds. > Not exactly, this issue is not specific to camera. If you look at the num= bers in the > commit text, even for the test device its the same observation. It depend= s on > the buffer size we are unmapping which affects the number of TLBIs issue.= I am > not aware of any such HW side bw issues for camera specifically on QCOM > devices. It is clear that reducing number of TLBIs reduces the umap API latency. Bu= t, It is at the expense of throwing away valid tlb entries.=20 Quantifying the impact of arbitrary invalidation of valid tlb entries at co= ntext level is not straight forward and use case dependent. The side-effects might be rare or won't be known until = they are noticed. Can you provide more details on How the unmap latency is causing camera to = drop frames? Is unmap performed in the perf path? If unmap is queued and performed on a back ground thread, would it resolve = the frame drops? -KR 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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_RED autolearn=no 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 C7F4BC48BD1 for ; Fri, 11 Jun 2021 16:50:04 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 67951613C3 for ; Fri, 11 Jun 2021 16:50:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 67951613C3 Authentication-Results: mail.kernel.org; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" Hi Sai, > >> > No, the unmap latency is not just in some test case written, the > >> > issue is very real and we have workloads where camera is reporting > >> > frame drops because of this unmap latency in the order of 100s of > milliseconds. > Not exactly, this issue is not specific to camera. If you look at the numbers in the > commit text, even for the test device its the same observation. It depends on > the buffer size we are unmapping which affects the number of TLBIs issue. I am > not aware of any such HW side bw issues for camera specifically on QCOM > devices. It is clear that reducing number of TLBIs reduces the umap API latency. But, It is at the expense of throwing away valid tlb entries. Quantifying the impact of arbitrary invalidation of valid tlb entries at context level is not straight forward and use case dependent. The side-effects might be rare or won't be known until they are noticed. Can you provide more details on How the unmap latency is causing camera to drop frames? Is unmap performed in the perf path? If unmap is queued and performed on a back ground thread, would it resolve the frame drops? -KR _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu 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=-4.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 5658AC48BE0 for ; Fri, 11 Jun 2021 16:52:15 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 18912613BA for ; 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Fri, 11 Jun 2021 16:49:55 +0000 Received: from BY5PR12MB3764.namprd12.prod.outlook.com ([fe80::d05:4bca:ea51:15af]) by BY5PR12MB3764.namprd12.prod.outlook.com ([fe80::d05:4bca:ea51:15af%6]) with mapi id 15.20.4219.024; Fri, 11 Jun 2021 16:49:55 +0000 From: Krishna Reddy To: Sai Prakash Ranjan CC: Robin Murphy , "linux-arm-msm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "iommu@lists.linux-foundation.org" , Will Deacon , "linux-arm-kernel@lists.infradead.org" , Thierry Reding Subject: RE: [PATCH] iommu/io-pgtable-arm: Optimize partial walk flush for large scatter-gather list Thread-Topic: [PATCH] iommu/io-pgtable-arm: Optimize partial walk flush for large scatter-gather list Thread-Index: AQHXXT84btg0466hEE2rkvq94oyuZasMBHAAgACy+QCAAD6WAIAAB6mAgAAg2ACAAAWcgIAAPESAgACQdxCAAA05AIABAqfQ Date: Fri, 11 Jun 2021 16:49:54 +0000 Message-ID: References: <20210609145315.25750-1-saiprakash.ranjan@codeaurora.org> <35bfd245-45e2-8083-b620-330d6dbd7bd7@arm.com> <12067ffb8243b220cf03e83aaac3e823@codeaurora.org> <266f190e-99ae-9175-cf13-7a77730af389@arm.com> <61c69d23-324a-85d7-2458-dfff8df9280b@arm.com> <07001b4ed6c0a491eacce6e4dc13ab5e@codeaurora.org> In-Reply-To: <07001b4ed6c0a491eacce6e4dc13ab5e@codeaurora.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: codeaurora.org; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Sai, > >> > No, the unmap latency is not just in some test case written, the > >> > issue is very real and we have workloads where camera is reporting > >> > frame drops because of this unmap latency in the order of 100s of > milliseconds. > Not exactly, this issue is not specific to camera. If you look at the numbers in the > commit text, even for the test device its the same observation. It depends on > the buffer size we are unmapping which affects the number of TLBIs issue. I am > not aware of any such HW side bw issues for camera specifically on QCOM > devices. It is clear that reducing number of TLBIs reduces the umap API latency. But, It is at the expense of throwing away valid tlb entries. Quantifying the impact of arbitrary invalidation of valid tlb entries at context level is not straight forward and use case dependent. The side-effects might be rare or won't be known until they are noticed. Can you provide more details on How the unmap latency is causing camera to drop frames? Is unmap performed in the perf path? If unmap is queued and performed on a back ground thread, would it resolve the frame drops? -KR _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel