From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail19.out.titan.email (mail19.out.titan.email [3.64.226.213]) (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 69AE822FE0E for ; Tue, 21 Oct 2025 14:45:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=3.64.226.213 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761057935; cv=none; b=myJsgmk+wCsb2a1etq5ZKL/ldGpTKdnfkERvrfvD+3diobQ/mQrYvDrJ5kZOva9JxFdjrPJ8pmKIgUZSiWlN+0qFkJywNcSSmhp52NNwA5RB/Louw6Vv/B2HC/YZnuOD2D3A5vSRbj8hIkcnOU4ZQCMPSl9V40dBuveinizokQQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761057935; c=relaxed/simple; bh=AveatL9pt5Ba1OWtudoGfLD4mfWX2mDy+IqL3/ucg3I=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=bzLeJ8oTX13XQC1zlD4uE3kzRU8VCD1E9mudYcK1mK+OPAIbdK0n9NXEpshG9lK2pjqRswrVBdszgvEpCT1Qdb67rvN0lTpHg+MuY7mlQHqGJedgPdkGKrgmKPyRRtfV83E14zmnyRIliOcikd/9IbVDazch9B84ha8p+kU55vQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=techsingularity.net; spf=pass smtp.mailfrom=techsingularity.net; dkim=pass (1024-bit key) header.d=techsingularity.net header.i=@techsingularity.net header.b=F0J6y++B; arc=none smtp.client-ip=3.64.226.213 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=techsingularity.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=techsingularity.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=techsingularity.net header.i=@techsingularity.net header.b="F0J6y++B" Received: from localhost (localhost [127.0.0.1]) by smtp-out0101.titan.email (Postfix) with ESMTP id 4crZRG5WC2z4vxJ; Tue, 21 Oct 2025 14:28:42 +0000 (UTC) DKIM-Signature: a=rsa-sha256; bh=FT6F8lxdsXIxZJ5Uz5oR0Tp97ixFg9xUf4/QWCRvvM4=; c=relaxed/relaxed; d=techsingularity.net; h=from:message-id:mime-version:cc:subject:to:date:from:to:cc:subject:date:message-id:in-reply-to:reply-to:references; q=dns/txt; s=titan1; t=1761056922; v=1; b=F0J6y++BM6PQ1Y5ac9nn8uS9DDNbNiAG1BTqeusCXqE5AcY9wm4m/MxQsIGAgRTLs29EMcMe 7mx0Fs6+42wx+llq9Wt0/u5R990ioOSdGcsRRwnpYA9LVx3yxW8Xim7DfbG8nU5SaGegONbQc9I OfiO6LzrNiSode8VxiU4Neqo= Received: from morpheus.112glenside.lan (ip-84-203-16-53.broadband.digiweb.ie [84.203.16.53]) by smtp-out0101.titan.email (Postfix) with ESMTPA id 4crZRF3nhpz4vxF; Tue, 21 Oct 2025 14:28:41 +0000 (UTC) Feedback-ID: :mgorman@techsingularity.net:techsingularity.net:flockmailId From: Mel Gorman To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Ingo Molnar , Juri Lelli , Dietmar Eggemann , Valentin Schneider , Chris Mason , Mel Gorman Subject: [RFC PATCH 0/2] Reintroduce NEXT_BUDDY for EEVDF v2 Date: Tue, 21 Oct 2025 15:28:22 +0100 Message-ID: <20251021142824.3747201-1-mgorman@techsingularity.net> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-F-Verdict: SPFVALID X-Titan-Src-Out: 1761056922593006664.2237.8990852766471748465@prod-euc1-smtp-out1002. X-CMAE-Score: 0 X-CMAE-Analysis: v=2.4 cv=Rqw/LDmK c=1 sm=1 tr=0 ts=68f7989a a=SAet2ifMzLisiRUXZwfs3w==:117 a=SAet2ifMzLisiRUXZwfs3w==:17 a=CEWIc4RMnpUA:10 a=QcgZxE_Df_qfIiiupLUA:9 a=zgiPjhLxNE0A:10 I've been chasing down a number of schedule issues recently like many others and found they were broadly grouped as 1. Failure to boost CPU frequency with powersave/ondemand governors 2. Processors entering idle states that are too deep 3. Differences in wakeup latencies for wakeup-intensive workloads Adding topology into account means that there is a lot of machine-specific behaviour which may explain why some discussions recently have reproduction problems. Nevertheless, the removal of LAST_BUDDY and NEXT_BUDDY being disabled has an impact on wakeup latencies. This RFC is to determine if this is valid approach to prefer selecting a wakee if it's eligible to run even though other unrelated tasks are more eligible. kernel/sched/fair.c | 131 ++++++++++++++++++++++++++++++++++------ kernel/sched/features.h | 2 +- 2 files changed, 112 insertions(+), 21 deletions(-) -- 2.51.0