From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 BD8DF1804A for ; Sat, 1 Nov 2025 00:08:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761955710; cv=none; b=MjrZDDible2OcFibKgjxqozoq7FY4QgdzE4gPT8LYtFgfOaOqKULlXpJCUcnfHXaJD3n2sj56LFij/AlYhtIL8KX9WhUSmUKoRykrzVa6uwXapk9aKYBOQ4GbVfK4VMJZNlepREL9gzb3d7P19zJDprcpJQQE/k+L4L/ME8gidg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761955710; c=relaxed/simple; bh=pad/gjWGpUixHKSXyeTky6Rtp0C5JSdvHOBTuXBlQZM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GYJcc7moi/WYh3bqt9wD5DY2yssKNRjbqT1HLd2PDOq2HqZjIm1/DaNvutRMike2Hs9IKgGJ3MtVN8DWJS7a/hrU5NGFFrmbw8LvoPNPkOWchG7JNyNMMdg2nytdLmW0EA/N2+9XjKMUutFxfvqILXV+nulmmm8ezMNCu5Ou/1Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (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=mhBMGSIc; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (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="mhBMGSIc" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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=dkAgA5Pw3hOQfdBPhvZT0O/RXRqugoIYYaa/9/hEr9E=; b=mhBMGSIci7+07nNJ/GENxkVA9r IzwVdsOLLQWgAdZzpbJ5YRDUFImhmgIZr8t3mol+GTWfiocGF6prFZFRxXen301jP5Cj2VGZEG0RN HGJSTMcmi0Wt8BMXcy7KC4jXLzw67WB926MPNLDNJjSaUrZ6SItn1nNYJSbtAWJQIrvyzKZXfOdor jxNK7DAaAzETR8yTqcJSkxYyMhPlirtkmoIYMq9dW8dM4iSMrwhub3on1xSPNldnQhOMEmPL74Jq2 t5fnldaNvOHFQO0gcLJn9/JFmtM7CMB6wVCyaeBD7oWWXgN2WIX32aaKhKHPae4O6KloMFmfMl1ZB uT2Z1l8g==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1vEyIM-0000000CDrC-3V3s; Fri, 31 Oct 2025 23:12:53 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id BAA48300289; Sat, 01 Nov 2025 01:08:03 +0100 (CET) Date: Sat, 1 Nov 2025 01:08:03 +0100 From: Peter Zijlstra To: Gabriele Monaco Cc: Juri Lelli , linux-kernel@vger.kernel.org, Ingo Molnar , Clark Williams , arighi@nvidia.com Subject: Re: [RFC PATCH] sched/deadline: Avoid dl_server boosting with expired deadline Message-ID: <20251101000803.GA2212249@noisy.programming.kicks-ass.net> References: <20251014193300.GA1206438@noisy.programming.kicks-ass.net> <20251020141130.GJ3245006@noisy.programming.kicks-ass.net> <8dc29e28a4d87954378ef1d989e0374526b44723.camel@redhat.com> <20251030184205.GB2989771@noisy.programming.kicks-ass.net> <20251031130543.GV4068168@noisy.programming.kicks-ass.net> <1f2ad071e59db2ed8bc0b382ae202b7474d07afc.camel@redhat.com> <20251031152005.GT3245006@noisy.programming.kicks-ass.net> <2daa2e6217eeaa239616303626c0d73d808ae947.camel@redhat.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: <2daa2e6217eeaa239616303626c0d73d808ae947.camel@redhat.com> On Fri, Oct 31, 2025 at 04:41:22PM +0100, Gabriele Monaco wrote: > On Fri, 2025-10-31 at 16:20 +0100, Peter Zijlstra wrote: > > On Fri, Oct 31, 2025 at 02:24:17PM +0100, Gabriele Monaco wrote: > > > > > > Different scenario if I have the CPU busy with other tasks (e.g. RT > > > policies), there I can see the server stopping and starting again. > > > After I do this I seem to get a different behaviour (even some boosting > > > after idle), I'm trying to understand what's going on. > > > > > After running some heavy RT workload (stress-ng --cpu 10 --sched rr) I do see > the server stopping and starting as the models would expect, but somehow it's > always boosting as soon as it's started. > > Apparently dl_defer_running is always 1 in that scenario. Perhaps running idle > counts as running something too, so it never defers. But I can't really see how > this happens.. The transition [4], will retain dl_defer_running, such that a timely re-start of the dl_server can immediately run again.