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 A3D8E338F20 for ; Wed, 12 Nov 2025 14:48:29 +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=1762958913; cv=none; b=BL14+vl4EzPAZzQQTT1ae8LFFEcvyBZHyKL+VI0Wc432coMNd9EbTXFVBhFUpIAXelDXIaN7FC60iOC/aFnIVV7yqZlxnlQv+83W1ydjFjDFDhRw+NE+yudznh+vPuRPuw2p1FeROk7xyqixiBqOcuKGOx8oBN/hJ+iCd9R4+ag= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762958913; c=relaxed/simple; bh=o6/bL4MYU+f2UOEryFTp4L5qf1SWg3IyYODLr4T3ckA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LniwkwCtqQs/4fLrpHb4GKsicw5mAmYqFLyvQwN2semWTxEgv19/dGlqm26SELCAZ+eC0VL/E7PjLYYyfislxGQP95ksimuVe0K90H/gwDeeZQlbber4jhD2PYQXOuuIF/CwvTKAmg+F3/x3cqkF5uIcM+Ga+rUDOxEXWHtfuYs= 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=jofjwsss; 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="jofjwsss" 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=xP/7ZgPtLxO6wgz0uO/5plwH3ptvWelS/+FdkJ+O+UA=; b=jofjwsssjrOe152ppgR2/xg6Pk 5vTN3xXY5fl/bBBtqBFl5XOPJNvn1RKmdLOAJ5aEKzP4H+RWIo1tOQRitpPSb/JQT34MOIv7E9ZN8 dNVqEJt4fnKAEO/Gai/pgsarpxPrLc/JpUOBx8W6TH5sYrfZZotUQbOXQCMmCo7eZMYUp8a+N1kZI hlDy/CwLhHy7sJPluNqBtvs2sFg4ksUmGogwimys2kiB5jm1CXc6sEiCw5e8erXAVeo1SokzhmtSj MEaWCJQC7XYffrQxqHD8phOGAKKKNjfoDG7ZMqPP8NpDcu9LAXhhw3SRhJeXf/eK6Whv/D6uz9CB9 8gYVt8Rw==; 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 1vJBHN-0000000FdOq-0OuA; Wed, 12 Nov 2025 13:52:57 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 12F2E300265; Wed, 12 Nov 2025 15:48:23 +0100 (CET) Date: Wed, 12 Nov 2025 15:48:23 +0100 From: Peter Zijlstra To: Mel Gorman Cc: Ingo Molnar , Juri Lelli , Dietmar Eggemann , Valentin Schneider , Chris Mason , Madadi Vineeth Reddy , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] sched/fair: Reimplement NEXT_BUDDY to align with EEVDF goals Message-ID: <20251112144823.GE3245006@noisy.programming.kicks-ass.net> References: <20251112122521.1331238-1-mgorman@techsingularity.net> <20251112122521.1331238-3-mgorman@techsingularity.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: <20251112122521.1331238-3-mgorman@techsingularity.net> On Wed, Nov 12, 2025 at 12:25:21PM +0000, Mel Gorman wrote: > + /* Prefer picking wakee soon if appropriate. */ > + if (sched_feat(NEXT_BUDDY) && > + set_preempt_buddy(cfs_rq, wake_flags, pse, se)) { > + > + /* > + * Decide whether to obey WF_SYNC hint for a new buddy. Old > + * buddies are ignored as they may not be relevant to the > + * waker and less likely to be cache hot. > + */ > + if (wake_flags & WF_SYNC) > + preempt_action = preempt_sync(rq, wake_flags, pse, se); > + } Why only do preempt_sync() when NEXT_BUDDY? Nothing there seems to depend on buddies.