From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Widawsky Subject: Re: [PATCH] [RFT] drm/i915: Don't waste our paultry cache on a context object Date: Fri, 20 Sep 2013 08:24:44 -0700 Message-ID: <20130920152443.GA8348@bwidawsk.net> References: <1379689502-7462-1-git-send-email-benjamin.widawsky@intel.com> <20130920151237.GB10182@nuc-i3427.alporthouse.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail.bwidawsk.net (bwidawsk.net [166.78.191.112]) by gabe.freedesktop.org (Postfix) with ESMTP id 59F15E70AF for ; Fri, 20 Sep 2013 08:24:49 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20130920151237.GB10182@nuc-i3427.alporthouse.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: Chris Wilson , Ben Widawsky , Intel GFX , Eero Tamminen List-Id: intel-gfx@lists.freedesktop.org On Fri, Sep 20, 2013 at 04:12:37PM +0100, Chris Wilson wrote: > On Fri, Sep 20, 2013 at 08:05:02AM -0700, Ben Widawsky wrote: > > Context save and restore is by definition a slow process, however it is > > also an infrequent process. Don't try to optimize the save restore at > > the cost of any of our precious cache space. Contexts begin to get quite > > large on HSW and beyond. > > Infrequent? Relative to operations which use the cache. > > > At least for benchmarks people seem to care about, there is almost > > always only 1 context running, which means I don't expect this to do any > > harm. For benchmarks with many contexts, there could be performance > > degradation - but I have a sneaking suspicion the HW will do some fancy > > magic to speak up context save & restores anyway. > > There are at least 2 contexts in every benchmark QA cares about. It > wasn't like making them L3 objects in the first place was motivated by > benchmark results... > No, I've no doubt it was motivated by benchmarks, but I think making it L3 (which I still have a hard time believe would do at all what it's intended to do) would only prove further that not wasting LLC space is a good thing. The theory follows that not wasting L3 space is also a good thing. > Anyway the idea was to see if QA still notice a difference... > -Chris > I'll try to be an optimist for once. -- Ben Widawsky, Intel Open Source Technology Center