Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752540AbZKPSaG (ORCPT ); Mon, 16 Nov 2009 13:30:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751634AbZKPSaF (ORCPT ); Mon, 16 Nov 2009 13:30:05 -0500 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:41941 "EHLO www.etchedpixels.co.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751458AbZKPSaE (ORCPT ); Mon, 16 Nov 2009 13:30:04 -0500 Date: Mon, 16 Nov 2009 18:31:17 +0000 From: Alan Cox To: Linus Torvalds Cc: Ingo Molnar , Stijn Devriendt , Mike Galbraith , Peter Zijlstra , Andrea Arcangeli , Thomas Gleixner , Andrew Morton , peterz@infradead.org, linux-kernel@vger.kernel.org Subject: Re: [RFC] observe and act upon workload parallelism: PERF_TYPE_PARALLELISM (Was: [RFC][PATCH] sched_wait_block: wait for blocked threads) Message-ID: <20091116183117.48a02426@lxorguk.ukuu.org.uk> In-Reply-To: References: <1258311859-6189-1-git-send-email-HIGHGuY@gmail.com> <20091116083521.GC20672@elte.hu> X-Mailer: Claws Mail 3.7.3 (GTK+ 2.14.7; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1248 Lines: 30 On Mon, 16 Nov 2009 10:02:50 -0800 (PST) Linus Torvalds wrote: > > > On Mon, 16 Nov 2009, Ingo Molnar wrote: > > > > Regarding the API and your patch, i think we can and should do something > > different and more capable - while still keeping your basic idea: > > Actually, I'd suggest exactly the reverse. > > Yes, do something different, but _less_ capable, and much simpler: > introduce the notion of "grouped thread scheduling", where a _group_ of > threads gets scheduled as one thread. And preferably expose it so it can be used by groups of processes as well as just "threads" in the userspace shared pid etc sense. There are quite a few applications where both "only run one of us" and "don't pre-empt within the group" are a useful semantic (you often don't want the pre-empting within the group of threads because it messes up all the improved locking opportunities). In particular the usual buzz locks don't mix well with "only run one of us". Alan -- 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/