Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753141AbbKMWM3 (ORCPT ); Fri, 13 Nov 2015 17:12:29 -0500 Received: from mail.fireflyinternet.com ([87.106.93.118]:55326 "EHLO fireflyinternet.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752990AbbKMWM0 (ORCPT ); Fri, 13 Nov 2015 17:12:26 -0500 X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Date: Fri, 13 Nov 2015 22:12:12 +0000 From: Chris Wilson To: Jens Axboe Cc: Mike Galbraith , Daniel Vetter , DRI Development , LKML Subject: Re: __i915_spin_request() sucks Message-ID: <20151113221212.GJ569@nuc-i3427.alporthouse.com> Mail-Followup-To: Chris Wilson , Jens Axboe , Mike Galbraith , Daniel Vetter , DRI Development , LKML References: <5644F850.2060803@kernel.dk> <5644F941.9090505@kernel.dk> <20151112221908.GA26194@nuc-i3427.alporthouse.com> <56451812.2050704@kernel.dk> <20151113091558.GN6247@nuc-i3427.alporthouse.com> <20151113153629.GB8939@kernel.dk> <1447431225.5655.66.camel@gmail.com> <56460E5C.6000602@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56460E5C.6000602@kernel.dk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1175 Lines: 27 On Fri, Nov 13, 2015 at 09:22:52AM -0700, Jens Axboe wrote: > On 11/13/2015 09:13 AM, Mike Galbraith wrote: > >On Fri, 2015-11-13 at 08:36 -0700, Jens Axboe wrote: > >>Previous patch was obvious pre-coffee crap, this should work for using > >>ktime to spin max 1usec. > > > >1us seems a tad low. I doubt the little wooden gears and pulleys of my > >core2 Toshiba Satellite lappy can get one loop ground out in a usec :) > > Maybe it is, it's based off the original intent of the function, > though. See the original commit referenced. I've been looking at numbers from one laptop and I can set the timeout at 2us before we see a steep decline in what is more or less synchronous request handling (which affects a variety of rendering workloads). Looking around, other busy loops seem to use local_clock() (i.e. rdstcll with a fair wind). Is that worth using here? -Chris -- Chris Wilson, Intel Open Source Technology Centre -- 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/