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 BC21928D8F4 for ; Tue, 28 Oct 2025 19:04:28 +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=1761678272; cv=none; b=SSx8mloJ+GqU/1ZCWxiuxs16P6JZfgV8JEAzH9H65UzFFVgdTY8XJUoujhRveY0e63PRlu0XDoHaWmBteC64dWtTWaQkJFUtZryd0i5/XJFWxL2WlFSFMC1L+hp/gmz/PwUFuAlCjQS9QW8YSEGtnruwRPll3LlpTktPG25a0mo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761678272; c=relaxed/simple; bh=K/K0S9uNxaSOBN1rN5pdkkhmp7zyf8luqsky3wyoIBQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=qKiGgJiruKGMOEyp6fUn6YyLNOd/O0zMrQq8Rs4rZI8IKNZTKc+r4vg98XU4UCKcewgIL3oT7iogknalMy3euN+Rsl7fOfWzXTup9+3szuuCxSHVmOcODdhhodixODNxGkAuuZts/wpsmRuh7p2pqOF/nnri2mbeKFuVOzXAWa8= 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=OZQdB5iV; 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="OZQdB5iV" 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=BUFS8/GDoRKUssZ1xnDZcccJ1KTIaqWaEajKYESfb+k=; b=OZQdB5iV7ahZxUJD4keMym5PmU 4HI/IgiN21HNZE50SvnjiWrLOaL2fjCymXYFIsdoZVLslFDTSdXAymc8HpQXuUzIUjwhiZcV4u2VS 03VYQQ9ilY3hvkT3ZUwvuBxceMp/FUVpzremIExY7CewcFNiXAEtYggLEJJ3j5oBtxzKaYXpQdfTx TMERPGgJ6gLSi1viUKIYw8ZwR5Gmei3CZCfbqcLINLftdzdNKnnINrA39Spx9qurjFLRbqWUGOZ8s tmDVI6BCCYvFvnddVuuopyjlVLl7zhoaGiAZbPjbK+FQtz/aP8iQHN33YaBPGAwTLm2q/pB+jG/Fi LA9kZRvw==; 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 1vDo7o-000000056DK-21t8; Tue, 28 Oct 2025 18:08:52 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id C70B9300323; Tue, 28 Oct 2025 20:04:22 +0100 (CET) Date: Tue, 28 Oct 2025 20:04:22 +0100 From: Peter Zijlstra To: Namhyung Kim Cc: Ingo Molnar , Mark Rutland , Alexander Shishkin , Arnaldo Carvalho de Melo , Ian Rogers , Adrian Hunter , LKML , Eric Dumazet , Thomas Gleixner , Sebastian Andrzej Siewior Subject: Re: [PATCH] perf/x86: Add cond_resched() when allocate/release DS buffers Message-ID: <20251028190422.GE3419281@noisy.programming.kicks-ass.net> References: <20251027212724.1759322-1-namhyung@kernel.org> <20251028141518.GA4067720@noisy.programming.kicks-ass.net> <20251028152747.GR4068168@noisy.programming.kicks-ass.net> 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: On Tue, Oct 28, 2025 at 12:02:58PM -0700, Namhyung Kim wrote: > Hi Peter, > > On Tue, Oct 28, 2025 at 04:27:47PM +0100, Peter Zijlstra wrote: > > On Tue, Oct 28, 2025 at 03:15:18PM +0100, Peter Zijlstra wrote: > > > On Mon, Oct 27, 2025 at 02:27:24PM -0700, Namhyung Kim wrote: > > > > On large systems, it's possible to trigger sched latency warning during > > > > the DS buffer allocation or release. Add cond_resched() to avoid it. > > > > > > We're >.< close to deleting cond_resched(), it makes absolutely no sense > > > adding more. > > > > Specifically, IIRC the plan was to do something like the below after the > > next LTS release, and then continue to remove VOLUNTARY in subsequent > > releases, leaving NONE the only option for the legacy architectures that > > do not support preemption. > > Thanks for your review! > > I haven't followed the work in this area so was not aware of the > PREEMPT_LAZY. Looks great! I hope it'll work well on server platforms > with many batch jobs and interactive tasks. > > I will drop my patch then. Well, we've been trying to get people to test things... But realistically people will only test once you force them. So we'll see.