Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752474AbdCDQES (ORCPT ); Sat, 4 Mar 2017 11:04:18 -0500 Received: from mail-wm0-f51.google.com ([74.125.82.51]:35283 "EHLO mail-wm0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752550AbdCDQCs (ORCPT ); Sat, 4 Mar 2017 11:02:48 -0500 From: Paolo Valente To: Jens Axboe , Tejun Heo Cc: Fabio Checconi , Arianna Avanzini , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, ulf.hansson@linaro.org, linus.walleij@linaro.org, broonie@kernel.org, Paolo Valente Subject: [PATCH RFC 13/14] block, bfq: boost the throughput with random I/O on NCQ-capable HDDs Date: Sat, 4 Mar 2017 17:01:30 +0100 Message-Id: <20170304160131.57366-14-paolo.valente@linaro.org> X-Mailer: git-send-email 2.10.0 In-Reply-To: <20170304160131.57366-1-paolo.valente@linaro.org> References: <20170304160131.57366-1-paolo.valente@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2930 Lines: 65 This patch is basically the counterpart, for NCQ-capable rotational devices, of the previous patch. Exactly as the previous patch does on flash-based devices and for any workload, this patch disables device idling on rotational devices, but only for random I/O. In fact, only with these queues disabling idling boosts the throughput on NCQ-capable rotational devices. To not break service guarantees, idling is disabled for NCQ-enabled rotational devices only when the same symmetry conditions considered in the previous patches hold. Signed-off-by: Paolo Valente Signed-off-by: Arianna Avanzini --- block/bfq-iosched.c | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index e509237..10d550b 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -6372,20 +6372,15 @@ static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq) * The next variable takes into account the cases where idling * boosts the throughput. * - * The value of the variable is computed considering that - * idling is usually beneficial for the throughput if: + * The value of the variable is computed considering, first, that + * idling is virtually always beneficial for the throughput if: * (a) the device is not NCQ-capable, or * (b) regardless of the presence of NCQ, the device is rotational - * and the request pattern for bfqq is I/O-bound (possible - * throughput losses caused by granting idling to seeky queues - * are mitigated by the fact that, in all scenarios where - * boosting throughput is the best thing to do, i.e., in all - * symmetric scenarios, only a minimal idle time is allowed to - * seeky queues). + * and the request pattern for bfqq is I/O-bound and sequential. * * Secondly, and in contrast to the above item (b), idling an * NCQ-capable flash-based device would not boost the - * throughput even with intense I/O; rather it would lower + * throughput even with sequential I/O; rather it would lower * the throughput in proportion to how fast the device * is. Accordingly, the next variable is true if any of the * above conditions (a) and (b) is true, and, in particular, @@ -6393,7 +6388,8 @@ static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq) * device. */ idling_boosts_thr = !bfqd->hw_tag || - (!blk_queue_nonrot(bfqd->queue) && bfq_bfqq_IO_bound(bfqq)); + (!blk_queue_nonrot(bfqd->queue) && bfq_bfqq_IO_bound(bfqq) && + bfq_bfqq_idle_window(bfqq)); /* * The value of the next variable, @@ -8301,7 +8297,7 @@ static struct blkcg_policy blkcg_policy_bfq = { static int __init bfq_init(void) { int ret; - char msg[50] = "BFQ I/O-scheduler: v6"; + char msg[50] = "BFQ I/O-scheduler: v7r3"; #ifdef CONFIG_BFQ_GROUP_IOSCHED ret = blkcg_policy_register(&blkcg_policy_bfq); -- 2.10.0