From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:38216 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756576Ab2IDJcu (ORCPT ); Tue, 4 Sep 2012 05:32:50 -0400 Date: Tue, 4 Sep 2012 11:32:31 +0200 From: Alexander Gordeev To: Yinghai Lu Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Thomas Gleixner , Bjorn Helgaas , Suresh Siddha , Jeff Garzik , Matthew Wilcox , x86@kernel.org, linux-pci@vger.kernel.org, linux-ide@vger.kernel.org Subject: Re: [PATCH v2 -tip 1/5] x86, MSI: Support multiple MSIs in presense of IRQ remapping Message-ID: <20120904093230.GA17873@dhcp-26-207.brq.redhat.com> References: <034a9cbb168501954408f1004a28c827f3a4158b.1346653435.git.agordeev@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-pci-owner@vger.kernel.org List-ID: On Mon, Sep 03, 2012 at 11:53:39AM -0700, Yinghai Lu wrote: > On Mon, Sep 3, 2012 at 2:17 AM, Alexander Gordeev wrote: > You may update create_irq_nr to be __create_irq_nr, and it could take > extra count. > > and later have create_irq_nr to be __create_irq_nr(,1,) > and create_irqs to be __create_irq_nr(,count,) > .... Indeed. Will do. > BTW, in short, how much performance benefits for adding 500 lines code? Unfortunatelly, I do not have a short answer here. There are three types of performance this series deals with - I'll try to summarize: - devices - 3 SATA HDDs generate roughly one interrupt every 273 us while it get handled in less than 5 us. So there is/could be no increase here; - the hardware context interrupt handler - its performance dropped 2.5 times (little bit more in fact) at the expense of increase of 1.3 times in overall interrupt handling time (hardware context + threaded context); - overall system performance - I *assume* it should increase, because: (a) AHCI interrupt handlers keep local interrupts disabled 2.5 times less (b) separate AHCI IRQs become subjects of IRQ balancing (c) threaded handlers are per-device, per-CPU (well, up to irqbalanced) and executed with local interrupts enabled; -- Regards, Alexander Gordeev agordeev@redhat.com