From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chuck Ebbert Subject: Re: [PATCH RESEND v3 5/6] AHCI: Optimize single IRQ interrupt processing Date: Wed, 24 Sep 2014 08:27:12 -0500 Message-ID: <20140924082713.7ddd718e@as> References: <20140923205710.GB17332@mtj.dyndns.org> <20140924104213.GA2695@agordeev.usersys.redhat.com> <20140924130444.GA16555@htj.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ob0-f171.google.com ([209.85.214.171]:45181 "EHLO mail-ob0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753067AbaIXN1R (ORCPT ); Wed, 24 Sep 2014 09:27:17 -0400 In-Reply-To: <20140924130444.GA16555@htj.dyndns.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: Alexander Gordeev , linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org On Wed, 24 Sep 2014 09:04:44 -0400 Tejun Heo wrote: > Hello, Alexander. > > On Wed, Sep 24, 2014 at 11:42:15AM +0100, Alexander Gordeev wrote: > > On Tue, Sep 23, 2014 at 04:57:10PM -0400, Tejun Heo wrote: > > > Hmmm... how does it affect single device operation tho? It does make > > > individual interrupt handling heavier, no? > > > > I think it is difficult to assess "individual interrupt handling", since > > it depends from both the hardware and device access pattern. On the system > > I use the results are rather counter-intuitive: ahci_thread_fn() does not > > show up in perf report at all, nor ahci_single_irq_intr(). While before > > the change ahci_single_irq_intr() reported 0.00%. > > > > But since the handling is split in two parts it is rather incorrect to > > apply the same metric to the threaded context. Obviously, the threaded > > handler is expected slowed down by other interrupts handlers, but the > > whole system should benefit from it, which is exactly the aim of this > > change. > > Hmmm, how would the whole system benefit from it if there's only > single device? Each individual servicing of the interrupt does more > now which includes scheduling which may end up adding to completion > latency. > I think he meant other, non-AHCI, interrupt handlers would benefit. A good test of this patch might be to stream 10Gb ethernet while also streaming writes to an AHCI device.