From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 84A0B1E522; Thu, 14 Aug 2025 15:17:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755184632; cv=none; b=dlqMYiXrkP6uH+CGIBefjjH8KbGjryiHTveHI0TUOTY7pSD6fRvIBuWQbno8Zyml6kyo32StWDjmfBIAVUgSZo0SyEjtq7AMFzU5qERyu9fAKqMWJ9wFfrU5Vx90rfpNPYusI/16kUKMU3bOgblSUAvRZnjYHKMwG+YMzOysy9s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755184632; c=relaxed/simple; bh=qNO9HqA8hFJwdj2rfCz2c3nfuzWBv4KHkkzscMChIRQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=p8Enm4NwYMuTp6fScGf/v8Fr2sXOcuvdYMdKUiG/QuVsoYc3FlBdyhNPvgm4lJyR1fyF6Hr9BWCw2U9WCU+uNly06V0qIioq6wRrSQnsVC2er3SGq0wP6g+HB62PHpH7gFHTRdP036OKjPG6iXL/99zRuZ/CxeIXN9H/tsbCg6o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=tKRrFYmz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="tKRrFYmz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A4317C4CEF1; Thu, 14 Aug 2025 15:17:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755184631; bh=qNO9HqA8hFJwdj2rfCz2c3nfuzWBv4KHkkzscMChIRQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=tKRrFYmzIci9uqL/a8/Izgwv1VDid2XTIuaj7U/OW0D2BSA5p86kVM6j69O97MuWG S545dS8KmoZ8SDphvUE0tMyN9/dIur5LlIO+QAqzmHHx5O0UeeQGv/waKUjrP3E90h yEeQ6buPGQ2o/v00hbobf6lIPAxbPcDKm/EvvqmU= Date: Thu, 14 Aug 2025 17:17:07 +0200 From: Greg Kroah-Hartman To: Jiri Slaby Cc: stable@vger.kernel.org, patches@lists.linux.dev, Chris Mason , "Peter Zijlstra (Intel)" , Juri Lelli , Sasha Levin Subject: Re: [PATCH 6.16 199/627] sched/deadline: Less agressive dl_server handling Message-ID: <2025081451-geography-anchor-57a6@gregkh> References: <20250812173419.303046420@linuxfoundation.org> <20250812173426.853672780@linuxfoundation.org> <17955c87-1a82-4eae-94ee-3ac1447d4e71@kernel.org> <58c46200-95b0-4cd8-bb5e-44f963a66875@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <58c46200-95b0-4cd8-bb5e-44f963a66875@kernel.org> On Thu, Aug 14, 2025 at 10:37:22AM +0200, Jiri Slaby wrote: > On 14. 08. 25, 10:22, Jiri Slaby wrote: > > Hi, > > > > > > On 12. 08. 25, 19:28, Greg Kroah-Hartman wrote: > > > 6.16-stable review patch.  If anyone has any objections, please let > > > me know. > > > > > > ------------------ > > > > > > From: Peter Zijlstra > > > > > > [ Upstream commit cccb45d7c4295bbfeba616582d0249f2d21e6df5 ] > > > > > > Chris reported that commit 5f6bd380c7bd ("sched/rt: Remove default > > > bandwidth control") caused a significant dip in his favourite > > > benchmark of the day. Simply disabling dl_server cured things. > > > > > > His workload hammers the 0->1, 1->0 transitions, and the > > > dl_server_{start,stop}() overhead kills it -- fairly obviously a bad > > > idea in hind sight and all that. > > > > > > Change things around to only disable the dl_server when there has not > > > been a fair task around for a whole period. Since the default period > > > is 1 second, this ensures the benchmark never trips this, overhead > > > gone. > > > > This causes: > > sched: DL replenish lagged too much > > > > Maybe some prereq missing? > > Not really, this is present both in linus/master and tip/master. > > > Fixes: 557a6bfc662c ("sched/fair: Add trivial fair server") > > > Reported-by: Chris Mason > > > Signed-off-by: Peter Zijlstra (Intel) > > > Reviewed-by: Juri Lelli > > > Acked-by: Juri Lelli > > > Link: https://lkml.kernel.org/r/20250702121158.465086194@infradead.org > > > Signed-off-by: Sasha Levin > > > > thanks, Ok, I'll move this out of this release and queue it up for the "next one". thanks, greg k-h