Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751526AbaJFHSe (ORCPT ); Mon, 6 Oct 2014 03:18:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48616 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750888AbaJFHSc (ORCPT ); Mon, 6 Oct 2014 03:18:32 -0400 Date: Mon, 6 Oct 2014 08:27:11 +0100 From: Alexander Gordeev To: Tejun Heo Cc: linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org Subject: Re: [PATCH RESEND v3 5/6] AHCI: Optimize single IRQ interrupt processing Message-ID: <20141006072710.GH8971@agordeev.usersys.redhat.com> References: <20140923205710.GB17332@mtj.dyndns.org> <20140924104213.GA2695@agordeev.usersys.redhat.com> <20140924130444.GA16555@htj.dyndns.org> <20140924140844.GB2695@agordeev.usersys.redhat.com> <20140924143913.GH16555@htj.dyndns.org> <20141001153114.GE8971@agordeev.usersys.redhat.com> <20141005022311.GD8549@htj.dyndns.org> <20141005161646.GB22223@mtj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141005161646.GB22223@mtj.dyndns.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 05, 2014 at 12:16:46PM -0400, Tejun Heo wrote: > I think the thing which bothers me is that due to softirq we end up > bouncing the context twice. IRQ schedules threaded IRQ handler after > doing minimal amount of work. The threaded IRQ handler gets scheduled > and again it doesn't do much but basically just schedules block > softirq to actually run completions which is the heavier part. > Apparently this doesn't seem to hurt measureably but it's just weird. Hi Tejun, That is exactly the point I was concerned with when stated in one of changelogs "The downside of this change is introduction of a kernel thread". Splitting the service routine in two parts is a small change (in terms of code familiarity). Yet it right away provides benefits I could observe and justify (to myself at least). > Why are we bouncing the context twice? I *did* consider moving the threaded handler code to the softirq part. I just wanted to get updates in stages: to address hardware interrupts latency first and possibly threaded hander next. Getting done these two together would be too big change for me ;) > -- > tejun -- Regards, Alexander Gordeev agordeev@redhat.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/