From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH v2 02/11] locking/ww_mutex: Re-check ww->ctx in the inner optimistic spin loop Date: Tue, 6 Dec 2016 19:29:35 +0100 Message-ID: <20161206182935.GD3107@twins.programming.kicks-ass.net> References: <1480601214-26583-1-git-send-email-nhaehnle@gmail.com> <1480601214-26583-3-git-send-email-nhaehnle@gmail.com> <20161206150620.GT3045@worktop.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:4978:20e::2]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3EE966E3EF for ; Tue, 6 Dec 2016 18:29:45 +0000 (UTC) Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Waiman Long Cc: Maarten Lankhorst , Nicolai =?iso-8859-1?Q?H=E4hnle?= , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Ingo Molnar List-Id: dri-devel@lists.freedesktop.org T24gVHVlLCBEZWMgMDYsIDIwMTYgYXQgMTE6MDM6MjhBTSAtMDUwMCwgV2FpbWFuIExvbmcgd3Jv dGU6Cj4gCj4gVGhlIG11dGV4X3NwaW5fb25fb3duZXIoKSBmdW5jdGlvbiB3YXMgb3JpZ2luYWxs eSBtYXJrZWQgbm9pbmxpbmUKPiBiZWNhdXNlIGl0IGNvdWxkIGJlIGEgbWFqb3IgY29uc3VtZXIg b2YgQ1BVIGN5Y2xlcyBpbiBhIGNvbnRlbmRlZCBsb2NrLgo+IEhhdmluZyBpdCBzaG93biBzZXBh cmF0ZWx5IGluIHRoZSBwZXJmIG91dHB1dCB3aWxsIGhlbHAgdGhlIHVzZXJzIGhhdmUgYQo+IGJl dHRlciB1bmRlcnN0YW5kaW5nIG9mIHdoYXQgaXMgY29uc3VtaW5nIGFsbCB0aGUgQ1BVIGN5Y2xl cy4gU28gSSB3b3VsZAo+IHN0aWxsIGxpa2UgdG8ga2VlcCBpdCB0aGlzIHdheS4KCmFoISwgSSB0 cmllZCB0byBkaWcgdGhyb3VnaCBoaXN0b3J5IGJ1dCBjb3VsZG4ndCBmaW5kIGEgcmVhc29uIGZv ciBpdC4KCj4gCj4gSWYgeW91IGhhdmUgY29uY2VybiBhYm91dCBhZGRpdGlvbmFsIGxhdGVuY3kg Zm9yIG5vbi13d19tdXRleCBjYWxscywgb25lCj4gYWx0ZXJuYXRpdmUgY2FuIGJlOgoKVGhhdCdz IHByZXR0eSBob3JyaWZpYyA6LwpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fXwpkcmktZGV2ZWwgbWFpbGluZyBsaXN0CmRyaS1kZXZlbEBsaXN0cy5mcmVlZGVz a3RvcC5vcmcKaHR0cHM6Ly9saXN0cy5mcmVlZGVza3RvcC5vcmcvbWFpbG1hbi9saXN0aW5mby9k cmktZGV2ZWwK From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753630AbcLFTIn (ORCPT ); Tue, 6 Dec 2016 14:08:43 -0500 Received: from merlin.infradead.org ([205.233.59.134]:37388 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752355AbcLFTIl (ORCPT ); Tue, 6 Dec 2016 14:08:41 -0500 Date: Tue, 6 Dec 2016 19:29:35 +0100 From: Peter Zijlstra To: Waiman Long Cc: Nicolai =?iso-8859-1?Q?H=E4hnle?= , linux-kernel@vger.kernel.org, Nicolai =?iso-8859-1?Q?H=E4hnle?= , Ingo Molnar , Maarten Lankhorst , Daniel Vetter , Chris Wilson , dri-devel@lists.freedesktop.org Subject: Re: [PATCH v2 02/11] locking/ww_mutex: Re-check ww->ctx in the inner optimistic spin loop Message-ID: <20161206182935.GD3107@twins.programming.kicks-ass.net> References: <1480601214-26583-1-git-send-email-nhaehnle@gmail.com> <1480601214-26583-3-git-send-email-nhaehnle@gmail.com> <20161206150620.GT3045@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 06, 2016 at 11:03:28AM -0500, Waiman Long wrote: > > The mutex_spin_on_owner() function was originally marked noinline > because it could be a major consumer of CPU cycles in a contended lock. > Having it shown separately in the perf output will help the users have a > better understanding of what is consuming all the CPU cycles. So I would > still like to keep it this way. ah!, I tried to dig through history but couldn't find a reason for it. > > If you have concern about additional latency for non-ww_mutex calls, one > alternative can be: That's pretty horrific :/