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_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 5A10FC433FF for ; Fri, 2 Aug 2019 14:33:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 29D2D21726 for ; Fri, 2 Aug 2019 14:33:33 +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="Q72XB1jM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2394969AbfHBOdc (ORCPT ); Fri, 2 Aug 2019 10:33:32 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:57368 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731131AbfHBOdb (ORCPT ); Fri, 2 Aug 2019 10:33:31 -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=rgOIxhvmzzRkxe+QepP7XIs/hwgiVex6JxHcwodnLQc=; b=Q72XB1jMyU/8NpNSF0oqEApFU C3dplxXJ8GMS3HZ/CblmNC4cz2iNERozDXsBXwKF8s2FBPpU4yuprWjRcX/xuAXQzn1om/mAbg2tn hAhrV8oL9WK+PjWNxKjnlp2aYnyt8nnLEUJk89u9UTm7YgR8s+4/v6l3Y5hNec0wvFmEXVhK0YzA/ tk1lpQ8dAV7BV6hi+OvQCWTW4HkfwknhGEGsNM+zY7VwPDbmYzIOOrRKw/DBU6S3xL2k2QVmxfjO/ VZs4wnQmYF1pvMfitzd8Unku9K/Z8QWo5w7Vf2fnqe3VpUXILNSbfhgwjNVcyRxFlpdQaMPC9kbTG iTs83bTUA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1htYcY-0002kW-Lw; Fri, 02 Aug 2019 14:33:26 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 6A501202953BA; Fri, 2 Aug 2019 16:33:24 +0200 (CEST) Date: Fri, 2 Aug 2019 16:33:24 +0200 From: Peter Zijlstra To: Qais Yousef Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, Geert Uytterhoeven , Thomas Gleixner Subject: Re: [PATCH 0/5] Fix FIFO-99 abuse Message-ID: <20190802143324.GH2332@hirez.programming.kicks-ass.net> References: <20190801111348.530242235@infradead.org> <20190801131707.5rpyydznnhz474la@e107158-lin.cambridge.arm.com> <20190802093244.GF2332@hirez.programming.kicks-ass.net> <20190802102611.54sae3onftck5fye@e107158-lin.cambridge.arm.com> <20190802124151.GG2332@hirez.programming.kicks-ass.net> <20190802140854.ixq4cmo5nsfdaj24@e107158-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190802140854.ixq4cmo5nsfdaj24@e107158-lin.cambridge.arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 02, 2019 at 03:08:54PM +0100, Qais Yousef wrote: > On 08/02/19 14:41, Peter Zijlstra wrote: > > On Fri, Aug 02, 2019 at 11:26:12AM +0100, Qais Yousef wrote: > > > > > Yes a somewhat enforced default makes more sense to me. I assume you no longer > > > want to put the kthreads that just need to be above OTHER in FIFO-1? > > > > I'm not sure, maybe, there's not that many of them, but possibly we add > > another interface for them. > > By the way, did you see this one which is set to priority 16? > > https://elixir.bootlin.com/linux/v5.3-rc2/source/drivers/gpu/drm/msm/msm_drv.c#L523 I did, I ignored it because it wasn't 99 or something silly like that, but I'd definitely mop it up when doing the proposed. > > Also; like said before, the admin had better configure. > > I agree. But I don't think an 'admin' is an easily defined entity for all > systems. On mobile, is it the SoC vendor, Android framework, or the > handset/platform vendor/integrator? Mostly Android I suspect, but if SoC specific drivers have RT threads, it's their responsibility to integrate properly with the rest of Android of course. > > Also also, RR-SMP is actually broken (and nobody has cared enough to > > bother fixing it). > > If you can give me enough pointers to understand the problem I might be able to > bother with it :-) So the push-pull balancer we have (designed for FIFO but also applied to RR) will only move a task if the destination CPU has a lower prio. In the case where one CPU has 3 tasks and the other 1, and they're all the same prio, it does nothing. For FIFO that is fine, for RR, not so much. Because then the one CPU will RR between 3 tasks, giving each task 1/3rd, while the other will only run the one task.