From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Subject: Re: [PATCH] qla2xxx: Resolved a performance issue in interrupt handler Date: Tue, 9 Jun 2009 15:41:27 -0600 Message-ID: <20090609214127.GP3274@parisc-linux.org> References: <1244575944.12321.58.camel@mulgrave.site> <19C9538E-B7B2-4924-859F-37E56660D95E@qlogic.com> <1244580029.12321.138.camel@mulgrave.site> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from palinux.external.hp.com ([192.25.206.14]:52111 "EHLO mail.parisc-linux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754191AbZFIVlZ (ORCPT ); Tue, 9 Jun 2009 17:41:25 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Giridhar Malavali Cc: Anirban Chakraborty , linux-scsi@vger.kernel.org, douglas.w.styner@intel.com, James Bottomley , Peter Zijlstra On Tue, Jun 09, 2009 at 02:28:01PM -0700, Giridhar Malavali wrote: > On Jun 9, 2009, at 1:40 PM, James Bottomley wrote: >> It depends what the root cause is ... if it's really latency >> introduced >> by other interrupts, then IRQF_DISABLED might be the better course. >> If >> it's purely interrupt problems in the spin locked critical sections, >> then spin_lock_irq might be the better solution ... what would be >> useful >> is to have the test rig at intel which turned up the problem see what >> happens to the results for each case. > > Earlier, I have seen that when IRQ's are shared across multiple > controllers and if the first one to register (among shared controllers) > does not disable the IRQ with IRQF_DISABLED flag,then irrespective of the > IRQ registration from other controllers, the IRQ will be enabled by > default. With this behavior and qla2xxx sharing the IRQ, just disabling > the IRQ may not be sufficient. But MSI interrupts are never shared. Also, almost every driver *should* be using IRQF_DISABLED these days (there was a proposal to eliminate IRQF_DISABLED and force every driver to explicitly re-enable interrupts if it needed them on back in March). -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step."