From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754526AbcFPPj1 (ORCPT ); Thu, 16 Jun 2016 11:39:27 -0400 Received: from mail-bl2on0081.outbound.protection.outlook.com ([65.55.169.81]:50048 "EHLO na01-bl2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753840AbcFPPjX (ORCPT ); Thu, 16 Jun 2016 11:39:23 -0400 Authentication-Results: spf=pass (sender IP is 63.163.107.21) smtp.mailfrom=sandisk.com; lst.de; dkim=none (message not signed) header.d=none;lst.de; dmarc=bestguesspass action=none header.from=sandisk.com; X-AuditID: ac160c69-33fff70000000bcf-42-5762c6faafda Subject: Re: [PATCH 02/13] irq: Introduce IRQD_AFFINITY_MANAGED flag To: Christoph Hellwig References: <1465934346-20648-1-git-send-email-hch@lst.de> <1465934346-20648-3-git-send-email-hch@lst.de> <0412b942-ea0d-d4eb-c724-8243d12ff6f3@sandisk.com> <20160615102311.GA16619@lst.de> <67ef7a1c-56e1-db2c-b038-f9784fc1f52f@sandisk.com> <20160615151415.GA1919@localhost.localdomain> <7f0b16bd-b39f-99e6-c1c1-6a508bf9bbbf@sandisk.com> <20160615160316.GB1919@localhost.localdomain> <86aa652b-48d0-a7bb-683e-bf43939aa811@sandisk.com> <20160616152006.GA13615@lst.de> CC: Keith Busch , "tglx@linutronix.de" , "axboe@fb.com" , "linux-block@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "linux-kernel@vger.kernel.org" From: Bart Van Assche Message-ID: Date: Thu, 16 Jun 2016 17:39:07 +0200 User-Agent: Mozilla/5.0 (X11; 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Once we've got it in the core IRQ code we can tweak the > algorithm to be optimal. Sorry but I'm afraid that we are embedding policy in the kernel, something we should not do. I know that there are workloads for which dedicating some CPU cores to interrupt processing and other CPU cores to running kernel threads improves throughput, probably because this results in less cache eviction on the CPU cores that run kernel threads and some degree of interrupt coalescing on the CPU cores that process interrupts. My concern is that I doubt that there is an interrupt assignment scheme that works optimally for all workloads. Hence my request to preserve the ability to modify interrupt affinity from user space. Bart.