From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 79A9838B for ; Mon, 17 Mar 2025 10:31:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742207481; cv=none; b=At9EMfrgEiXxtN85y+bxMQfhoPkRsgHpkJOUJz9QMbFBqAPG0av2W9o8Bzh2jJN2hIHTz5n5sSsmSbG5cQgt0jZWwaK+b4UGd8Qzv0pVW8Z8WnSwFBrrUqTm5n5eDA7VY1N3KKy9UOB/la81EZeF58ds7qlOZrdWBaQjcnCDHEQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742207481; c=relaxed/simple; bh=p1kK8xRdVkgvTjsOb10aZe0DSNAANoFdjSyf/TKkmAA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=epMMgEc6YcmfrZbhi8nJ2609PqC9lBC6fQxN+GpDKGvB4A+1K/ZbbufSeBibNigdPMMCkcCpRVhTXh3bihVvrFN2qNAoXWGHjw+20/4+OvdacjAht0Hl7JZrv6wI2KpRsP0WStgn+Df82aLNikJeFllcLLu2xTUHDDWQ0VDL4Wc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=aXlsJW0f; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="aXlsJW0f" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=+fhTvmuo/XJpQAoRNZixWJv0sOe/uwdvXPJsR9JrbwE=; b=aXlsJW0f1pTvcXWHh9oZMonMTT t89FJZPqAHSUT8JTE6uADzaKRWPF5c8sfZYutvQHdtrX4/27L/KMFMBEUNlV6SVwjtOiNnjZ5nxYu dDIM2dEFVEfZDtPzATge6e9V6606sQTE8cUjGr+qqlyQsmVvnrc+KYPefDUDqri9ZeKdrEA56NfvJ Cg0XoNI8yXES9DGD/1ftoQPiYPJdVcAvRAjUnveSBrrgNuOYutW4ajNkpldhM5CF6cQoAlIU97Fo0 3+NlElpDleIRBmw7N3dXhDUzZlnnB3B9zB87b7D0oAs0C1/CClMN4sRPQQgxBT4h58mfjLhzfRCOY +/Sv5uWQ==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tu7kM-00000008V67-22Mz; Mon, 17 Mar 2025 10:31:02 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 6F141300783; Mon, 17 Mar 2025 11:31:01 +0100 (CET) Date: Mon, 17 Mar 2025 11:31:01 +0100 From: Peter Zijlstra To: Joel Fernandes Cc: linux-kernel@vger.kernel.org, Andrea Righi , Tejun Heo , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , David Vernet , Changwoo Min , Luigi De Matteis , paulmck@kernel.org, boqun.feng@gmail.com Subject: Re: [PATCH RFC 3/8] sched/ext: Add a DL server for sched_ext tasks Message-ID: <20250317103101.GC34541@noisy.programming.kicks-ass.net> References: <20250315022158.2354454-1-joelagnelf@nvidia.com> <20250315022158.2354454-4-joelagnelf@nvidia.com> <20250315072225.GG36322@noisy.programming.kicks-ass.net> <3b244939-6d55-4d86-8b77-a9a7629f8239@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3b244939-6d55-4d86-8b77-a9a7629f8239@nvidia.com> On Sat, Mar 15, 2025 at 07:15:27PM -0400, Joel Fernandes wrote: > > > On 3/15/2025 3:22 AM, Peter Zijlstra wrote: > > On Fri, Mar 14, 2025 at 10:21:50PM -0400, Joel Fernandes wrote: > >> sched_ext currently suffers starvation due to RT. The same workload when > >> converted to EXT can get zero runtime if RT is 100% running, causing EXT > >> processes to stall. Fix it by adding a DL server for EXT. > > > > This needs a lot more words on why you need a second server. Because I > > don't think you do. > > Sure, I will add more words to the change log to explain rationale. When you say > "I don't think you do", do you mean that both FAIR and EXT could be served by > the same server? Yeah, because now you get two deadline entities both having a reservation on bandwidth. One of which is not going to be used -- this is not nice. > If so, that will not handle the case where the system has both > FAIR and EXT tasks in the mix (EXT has a partial mode where certain tasks can be > made EXT with certain others left as FAIR) and FAIR runs 100% and starves EXT. Well, you did not mention that issue, you only babbled about RT. I did point out that issue with ext, and TJ said this mixed mode wasn't really meant to be used or somesuch. So if that's changed, this needs a separate discussion. Also; I gotta ask, why is nvidia looking at ext ?