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 5EF1437A3C8 for ; Thu, 30 Oct 2025 18:42:08 +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=1761849730; cv=none; b=bpMO8yHO0NJLEEpJKIqoOk76R1JCQG4bYX2FjarFCd59l7DjPujnclHLqKVvw6nfJA0yl1rNvzvEErxVQv8IlIub7rU7icNs1D9SCS6fdTImWt9mNXzmgXIRu1kSoWnP3eauuMp+sQdsGz+J9gS1Dp7qgdLT/SDiQ/zypKE1wLk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761849730; c=relaxed/simple; bh=qfWVp/47gDYfMV04cUy/+JxeEB45pBCZPvYNWIkA2Tg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=H43foorXPOWaA6jUAq9Q9XQqtWnYBnJZMS3bsoobshpSSSjxQ5rMINq7BYHkGOtBhODxWnUF6omLv/k3UwulqGqR/6X1yVhUICKmlX6BYnvW4XD71l5GkQEcONDCRVWQlqMChVIPqDCyyCpzgPedZffuoadYwODOXx3I2J+vSkk= 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=jhj+rZRc; 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="jhj+rZRc" 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=VuDtk6Wfak+z/PHOCu2vMlEQrltrT5X8Ug5SksNAYSo=; b=jhj+rZRcsQ4+mzhzN3eGx8eXO/ WVoRqVsbq7J2wsK8BfEZRlW8UpXjG0GDrC+/pWxA+ruzWXQCXA3L9jH84jHZo++nb8rRe7gWXhwtK NBZuFe48KzwzpWIstySmJVpMav6Ss7kbjQWMeijIcG38T4PDfP8lmFG+Y9y4PTUPU3a1GRRmph7Vq RukM91dVr0Rfv7VxMsftfBKXGcHjvXMRkwPZU3twV/59z9VDHyhomeoavg0k/9uPicAF2ziWBTG5G 4pK5tR0gWSmO/7woJPztGCQqGsTuVABbJYyvfcKWA+Wo3JcemUr2bG+mJBTHBl0rBn1+9aylft8t5 mI/X4S0Q==; 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 1vEWjL-00000009m0N-1s8q; Thu, 30 Oct 2025 17:46:35 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 5143C30029E; Thu, 30 Oct 2025 19:42:05 +0100 (CET) Date: Thu, 30 Oct 2025 19:42:05 +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: <20251030184205.GB2989771@noisy.programming.kicks-ass.net> References: <20251007122904.31611-1-gmonaco@redhat.com> <20251014095407.GM4067720@noisy.programming.kicks-ass.net> <20251014102541.GS3245006@noisy.programming.kicks-ass.net> <83a5971ef07226737421737f889795ec57b6fa6c.camel@redhat.com> <20251014193300.GA1206438@noisy.programming.kicks-ass.net> <20251020141130.GJ3245006@noisy.programming.kicks-ass.net> <8dc29e28a4d87954378ef1d989e0374526b44723.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: <8dc29e28a4d87954378ef1d989e0374526b44723.camel@redhat.com> On Wed, Oct 22, 2025 at 12:11:51PM +0200, Gabriele Monaco wrote: Sorry, finally cycling back to this. > > So how about something like this for starters? > > > > Thanks Peter for sharing this patch, I run it through my test and the model > seems to pass (i.e. no more boosting after deadline). What I found curious > however, is that throughout the test, servers went only through replenish > events. > The system under test is mostly idle (6 periodic dl tasks on a 16 CPUs virtme-ng > VM), so I expect not to see any task boosted by the servers, but in 5 minutes I > didn't even observe any start/stop for the server. > > I'm not sure why this is happening, but looking at traces it seems replenish > occurs more often and perhaps doesn't let the server stop: > > -0 [009] d.h3. 14.312395: (+950124) event_nomiss: -9: idle x dl_replenish_idle -> idle > -0 [009] d.h3. 14.312401: (+6) sched_dl_replenish: comm=server pid=-9 runtime=50000000 deadline=15253307235 yielded=0 > -0 [009] d.h3. 15.262771: (+950370) event_nomiss: -9: idle x dl_replenish_idle -> idle > -0 [009] d.h3. 15.262781: (+10) sched_dl_replenish: comm=server pid=-9 runtime=50000000 deadline=16203668554 yielded=0 > -0 [009] d.h3. 16.213117: (+950336) event_nomiss: -9: idle x dl_replenish_idle -> idle > -0 [009] d.h3. 16.213123: (+6) sched_dl_replenish: comm=server pid=-9 runtime=50000000 deadline=17154029879 yielded=0 > > Is this expected? Sort of, that was next on the list. Let me see if I can make it stop a little more.