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,USER_AGENT_GIT autolearn=unavailable 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 6637EC43215 for ; Tue, 19 Nov 2019 05:49:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 37BC021783 for ; Tue, 19 Nov 2019 05:49:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574142557; bh=XTKduqN7mHhES6KQ6cLQz/6SZSC+gMKdX1Jkj9OtVMY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=OjJZHQeE+3Z1WRPUErjjg4u6LKLoXXdTr6FYhGg+3nv9l2knb7eei0R0qPYVQ5jWs 46aRbRH5f7UItXe82FXIjRviWGcW2jWoJuea5YPu27kzdewgIUkdmDxxvb2yDZPJfp D4sFIGcWG3cA5FWtZcXAYogtTUR/y5+F+rlQoD6U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731466AbfKSFtQ (ORCPT ); Tue, 19 Nov 2019 00:49:16 -0500 Received: from mail.kernel.org ([198.145.29.99]:45888 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730779AbfKSFtN (ORCPT ); Tue, 19 Nov 2019 00:49:13 -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 58A37208C3; Tue, 19 Nov 2019 05:49:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574142552; bh=XTKduqN7mHhES6KQ6cLQz/6SZSC+gMKdX1Jkj9OtVMY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RBygYwKIw7oruLMZG0sFuS1arLj77J93Rn387YR6+nBDs+gytXaX053q8K6oGZYi4 T/kufXkaCqS/GdsSnO3QvFjlTpeVvh6QHWvGlaAMI3XN6G4jjdFP8geXYIwXoV5FKQ se9agfvqfDlycFArCuU/Ehz93dhcQQWCQ/p4LWb0= 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 4.14 119/239] blok, bfq: do not plug I/O if all queues are weight-raised Date: Tue, 19 Nov 2019 06:18:39 +0100 Message-Id: <20191119051329.460723697@linuxfoundation.org> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191119051255.850204959@linuxfoundation.org> References: <20191119051255.850204959@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 e65b0da1007b4..93863c6173e66 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -3314,7 +3314,12 @@ static bool bfq_bfqq_may_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 @@ -3326,7 +3331,8 @@ static bool bfq_bfqq_may_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