From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailgw02.mediatek.com (unknown [210.61.82.184]) (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 16B9E2EF2BC for ; Tue, 17 Jun 2025 15:54:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=210.61.82.184 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750175646; cv=none; b=Qc26ife19YpoOFysf0p3JcPNbdWukmKmoSkSBYOQPIVhfENDkAOemKn1VQqchgJxhJ/YzI0yjkvMr7w0LUIferXJEGwHPnELTyREJ7eDHFlokY/XbPoQ4TtjQFqGG6a//WHVUo7k9YAnB9WimrqP2o4YHuwdqP2U6Taz6eaSctw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750175646; c=relaxed/simple; bh=GixHo7OCVTSD0sJSxwSZMCjsg1quwRg/ut0ejA/F6/k=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=JUvKf5suKa3NHe9zMVosCzBczPA8vKPi8EH8/ePuBa6dyZSTVAuaCamcCaHmHk31A5Enl1DG5jFUVZqtCWplD/ct5V/bwJezo8ye8UFtmddEesQyMHj8WojjlLz9uFnNI6AnnuBSodmyQmLVcKmPeMUtALSPfgIrGXdFEsTisj4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mediatek.com; spf=pass smtp.mailfrom=mediatek.com; dkim=pass (1024-bit key) header.d=mediatek.com header.i=@mediatek.com header.b=Js1PFMfb; arc=none smtp.client-ip=210.61.82.184 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mediatek.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mediatek.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=mediatek.com header.i=@mediatek.com header.b="Js1PFMfb" X-UUID: 48305d404b9311f0b33aeb1e7f16c2b6-20250617 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mediatek.com; s=dk; h=Content-Type:Content-Transfer-Encoding:MIME-Version:Message-ID:Date:Subject:CC:To:From; bh=DM70jmBk+8+pNXMrSmDw0F0d1r4Q4LzFUoMuNsxPcH4=; b=Js1PFMfbr+Kni92Htg/UjrRVzwKN0SJuv+R9I0eBGAeZTW5YUG0Hb9xJYsGSMVqLNxO39RVkVAxTTOsdDTwrrlSRJYnkYNlT7qZlX+W6IFjbaTGraw0itmnfbN455gI1oEY0I0+WDtOFHxPN/uTwFEhcC35k33+CaEh7WSGoIwY=; X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.2.3,REQID:5b480e38-e146-42eb-84d7-2bc1e7194b3c,IP:0,UR L:0,TC:0,Content:-5,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION: release,TS:-5 X-CID-META: VersionHash:09905cf,CLOUDID:35561477-7521-4364-b0ef-cd7d9c0ecbde,B ulkID:nil,BulkQuantity:0,Recheck:0,SF:102,TC:nil,Content:0|50,EDM:-3,IP:ni l,URL:99|1,File:nil,RT:nil,Bulk:nil,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0, LES:1,SPR:NO,DKR:0,DKP:0,BRR:0,BRE:0,ARC:0 X-CID-BVR: 0 X-CID-BAS: 0,_,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR,TF_CID_SPAM_ULS X-CID-RHF: D41D8CD98F00B204E9800998ECF8427E X-UUID: 48305d404b9311f0b33aeb1e7f16c2b6-20250617 Received: from mtkmbs13n2.mediatek.inc [(172.21.101.108)] by mailgw02.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 773875663; Tue, 17 Jun 2025 23:53:59 +0800 Received: from mtkmbs11n1.mediatek.inc (172.21.101.185) by mtkmbs11n1.mediatek.inc (172.21.101.185) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1258.39; Tue, 17 Jun 2025 23:53:57 +0800 Received: from mtksitap99.mediatek.inc (10.233.130.16) by mtkmbs11n1.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.2.1258.39 via Frontend Transport; Tue, 17 Jun 2025 23:53:57 +0800 From: Kuyo Chang To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Matthias Brugger , AngeloGioacchino Del Regno CC: John Stultz , kuyo chang , , , Subject: [PATCH v2 1/1] sched/deadline: Fix dl_server runtime calculation formula Date: Tue, 17 Jun 2025 23:52:49 +0800 Message-ID: <20250617155355.1479777-1-kuyo.chang@mediatek.com> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-MTK: N From: kuyo chang [Symptom] The calculation formula for dl_server runtime is based on Frequency/capacity scale-invariance. This will cause excessive RT latency (expect absolute time). [Analysis] Consider the following case under a Big.LITTLE architecture: Assume the runtime is: 50,000,000 ns, and Frequency/capacity scale-invariance defined as below: Frequency scale-invariance: 100 Capacity scale-invariance: 50 First by Frequency scale-invariance, the runtime is scaled to 50,000,000 * 100 >> 10 = 4,882,812 Then by capacity scale-invariance, it is further scaled to 4,882,812 * 50 >> 10 = 238,418. So it will scaled to 238,418 ns. [Solution] The runtime for dl_server should be fixed time asis RT bandwidth control. Fix the runtime calculation formula for the dl_server. Signed-off-by: kuyo chang Acked-by: Juri Lelli Suggested-by: Peter Zijlstra v1: https://lore.kernel.org/all/20250614020524.631521-1-kuyo.chang@mediatek.com/ --- kernel/sched/deadline.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index ad45a8fea245..f68a158d01e9 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1504,7 +1504,9 @@ static void update_curr_dl_se(struct rq *rq, struct sched_dl_entity *dl_se, s64 if (dl_entity_is_special(dl_se)) return; - scaled_delta_exec = dl_scaled_delta_exec(rq, dl_se, delta_exec); + scaled_delta_exec = delta_exec; + if (!dl_se->dl_server) + scaled_delta_exec = dl_scaled_delta_exec(rq, dl_se, delta_exec); dl_se->runtime -= scaled_delta_exec; @@ -1624,7 +1626,9 @@ void dl_server_update_idle_time(struct rq *rq, struct task_struct *p) if (delta_exec < 0) return; - scaled_delta_exec = dl_scaled_delta_exec(rq, &rq->fair_server, delta_exec); + scaled_delta_exec = delta_exec; + if (!rq->fair_server.dl_server) + scaled_delta_exec = dl_scaled_delta_exec(rq, &rq->fair_server, delta_exec); rq->fair_server.runtime -= scaled_delta_exec; -- 2.45.2