From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5ACC3C46469 for ; Wed, 12 Sep 2018 17:42:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 01FEF20880 for ; Wed, 12 Sep 2018 17:42:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Df9TfgGm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 01FEF20880 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728043AbeILWsQ (ORCPT ); Wed, 12 Sep 2018 18:48:16 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:38878 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726862AbeILWsQ (ORCPT ); Wed, 12 Sep 2018 18:48:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=ENP3GbDyOQnD1mynbxYqp5fvvdRJktS2bf05jAAEepE=; b=Df9TfgGmQEYa6VHlPaG0aZX1Q E8PDDOleY7/dj4/+iBGSHjxk1h+iUMne3FCJJqCfckbPEb7V8yAFzOZXEzkkZs37r0GW07jF38TDi yxIB+6tBJQbOrpOcu2cRlce4Di/Uu4kHewpUQhCEeB5qtJRI49vW85nfJu8j4Ex+d83s8sYoZJsYq T5BV1wX+7KV/ud3h+qii3+cqNI/o7NGK4UGQ+awC3M2g2YDjOGMOBz97GgFLavzFC2A/wpUPCI/Uk el6hhrAsYUr2b1QgEa0GY/NgEHwZQBK72KyLPP2t7xjWgZ1/gUbQHhhI388v+yRWiONYZ4EmHuLnr L+04E+wZA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1g099x-0006x1-JM; Wed, 12 Sep 2018 17:42:37 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 1B349202C1A09; Wed, 12 Sep 2018 19:42:36 +0200 (CEST) Date: Wed, 12 Sep 2018 19:42:36 +0200 From: Peter Zijlstra To: Patrick Bellasi Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Ingo Molnar , Tejun Heo , "Rafael J . Wysocki" , Viresh Kumar , Vincent Guittot , Paul Turner , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan Subject: Re: [PATCH v4 02/16] sched/core: uclamp: map TASK's clamp values into CPU's clamp groups Message-ID: <20180912174236.GB24106@hirez.programming.kicks-ass.net> References: <20180828135324.21976-1-patrick.bellasi@arm.com> <20180828135324.21976-3-patrick.bellasi@arm.com> <20180912134945.GZ24106@hirez.programming.kicks-ass.net> <20180912155619.GG1413@e110439-lin> <20180912161218.GW24082@hirez.programming.kicks-ass.net> <20180912173515.GH1413@e110439-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180912173515.GH1413@e110439-lin> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 12, 2018 at 06:35:15PM +0100, Patrick Bellasi wrote: > On 12-Sep 18:12, Peter Zijlstra wrote: > > No idea; but if you want to go all fancy you can replace he whole > > uclamp_map thing with something like: > > > > struct uclamp_map { > > union { > > struct { > > unsigned long v : 10; > > unsigned long c : BITS_PER_LONG - 10; > > }; > > atomic_long_t s; > > }; > > }; > > That sounds really cool and scary at the same time :) > > The v:10 requires that we never set SCHED_CAPACITY_SCALE>1024 > or that we use it to track a percentage value (i.e. [0..100]). Or we pick 11 bits, it seems unlikely that capacity be larger than 2k. > One of the last patches introduces percentage values to userspace. > But, I was considering that in kernel space we should always track > full scale utilization values. > > The c:(BITS_PER_LONG-10) restricts the range of concurrently active > SE refcounting the same clamp value. Which, for some 32bit systems is > only 4 milions among tasks and cgroups... maybe still reasonable... Yeah, on 32bit having 4M tasks seems 'unlikely'.