From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 90D06C432C0 for ; Tue, 19 Nov 2019 06:07:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6389920672 for ; Tue, 19 Nov 2019 06:07:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574143634; bh=g6zAEREEgLTWT7LnJikRiT6qbd4YDdqTAfzWJ67n6H4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=xdecxgx74nvFgTZ9BK0lYBawlEOZ1grT0XJJhEnohdg4F6ges/3n+85742n7uq5lN 96VBAk1iFudKkEvMNN9+Hy9OdWbAL7vlSznS5VP7EoJqIX8iPZ4L2FviHgyL0wrRJH kNFO0lHNjDnw+aZG93Mvc/BduWfNi0ofkdZQm0y8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728953AbfKSGHN (ORCPT ); Tue, 19 Nov 2019 01:07:13 -0500 Received: from mail.kernel.org ([198.145.29.99]:54326 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727963AbfKSFdm (ORCPT ); Tue, 19 Nov 2019 00:33:42 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 37762222ED; Tue, 19 Nov 2019 05:33:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574141621; bh=g6zAEREEgLTWT7LnJikRiT6qbd4YDdqTAfzWJ67n6H4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1zvrWFeTx4gUPkg4OJ6IImyge7W28hQ2JUhkblvUAteZQfTSJW3QSB2d9L7D5EPjC kR2j0qVs/e6klo92CY/77jRp7opg8++OzrmrxpANMTKvnh8ma+5uL4Y7tEL3P5jI4H IFrtnhDMcds+bAiVKgOu+lJoVP01mGYngNnaaQeg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Paolo Valente , Jens Axboe , Sasha Levin Subject: [PATCH 4.19 221/422] blok, bfq: do not plug I/O if all queues are weight-raised Date: Tue, 19 Nov 2019 06:16:58 +0100 Message-Id: <20191119051412.950455318@linuxfoundation.org> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191119051400.261610025@linuxfoundation.org> References: <20191119051400.261610025@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Paolo Valente [ Upstream commit c8765de0adfcaaf4ffb2d951e07444f00ffa9453 ] To reduce latency for interactive and soft real-time applications, bfq privileges the bfq_queues containing the I/O of these applications. These privileged queues, referred-to as weight-raised queues, get a much higher share of the device throughput w.r.t. non-privileged queues. To preserve this higher share, the I/O of any non-weight-raised queue must be plugged whenever a sync weight-raised queue, while being served, remains temporarily empty. To attain this goal, bfq simply plugs any I/O (from any queue), if a sync weight-raised queue remains empty while in service. Unfortunately, this plugging typically lowers throughput with random I/O, on devices with internal queueing (because it reduces the filling level of the internal queues of the device). This commit addresses this issue by restricting the cases where plugging is performed: if a sync weight-raised queue remains empty while in service, then I/O plugging is performed only if some of the active bfq_queues are *not* weight-raised (which is actually the only circumstance where plugging is needed to preserve the higher share of the throughput of weight-raised queues). This restriction proved able to boost throughput in really many use cases needing only maximum throughput. Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/bfq-iosched.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 35ddaa820737c..66b1ebc21ce4f 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -3593,7 +3593,12 @@ static bool bfq_better_to_idle(struct bfq_queue *bfqq) * whether bfqq is being weight-raised, because * bfq_symmetric_scenario() does not take into account also * weight-raised queues (see comments on - * bfq_weights_tree_add()). + * bfq_weights_tree_add()). In particular, if bfqq is being + * weight-raised, it is important to idle only if there are + * other, non-weight-raised queues that may steal throughput + * to bfqq. Actually, we should be even more precise, and + * differentiate between interactive weight raising and + * soft real-time weight raising. * * As a side note, it is worth considering that the above * device-idling countermeasures may however fail in the @@ -3605,7 +3610,8 @@ static bool bfq_better_to_idle(struct bfq_queue *bfqq) * to let requests be served in the desired order until all * the requests already queued in the device have been served. */ - asymmetric_scenario = bfqq->wr_coeff > 1 || + asymmetric_scenario = (bfqq->wr_coeff > 1 && + bfqd->wr_busy_queues < bfqd->busy_queues) || !bfq_symmetric_scenario(bfqd); /* -- 2.20.1