From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751489AbeEGF4u convert rfc822-to-8bit (ORCPT ); Mon, 7 May 2018 01:56:50 -0400 Received: from mout.gmx.net ([212.227.17.21]:40035 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750732AbeEGF4r (ORCPT ); Mon, 7 May 2018 01:56:47 -0400 Message-ID: <1525672597.5064.3.camel@gmx.de> Subject: Re: [PATCH BUGFIX] block, bfq: postpone rq preparation to insert or merge From: Mike Galbraith To: Paolo Valente Cc: Jens Axboe , linux-block , LKML , Ulf Hansson , Mark Brown , linus.walleij@linaro.org, bfq-iosched@googlegroups.com, oleksandr@natalenko.name Date: Mon, 07 May 2018 07:56:37 +0200 In-Reply-To: <223CABEA-71E0-426F-A4AB-17BA8437C978@linaro.org> References: <20180504171701.6876-1-paolo.valente@linaro.org> <1525463210.622.1.camel@gmx.de> <1525508378.5406.6.camel@gmx.de> <9F155F9F-F6B2-465A-BA4D-A86FF6825071@linaro.org> <1525532191.5406.15.camel@gmx.de> <223CABEA-71E0-426F-A4AB-17BA8437C978@linaro.org> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.22.6 Mime-Version: 1.0 Content-Transfer-Encoding: 8BIT X-Provags-ID: V03:K1:b2gPUmqfIm+zZwYttxssSG5g+TN6p9kRTVQe8CBsdJtVpSRXU3x zZZWYnn2bvj+/jUtxP3JcY4Jvjknt4I1YiIBUXYGHbB3wuSkDyq67ZSOLT1Ay8mTnPD6761 S35okzAmxlAVhTNAbJneeTw8mN+AdRUtttdW4f1UErwiRn3NEei2WPqnFse2VRD9yhrRneP l6C9ufkO1C1QgeMoJg4Bw== X-UI-Out-Filterresults: notjunk:1;V01:K0:FtyHzbdF7/Y=:xhdWA1FMSwoGAVxwBDwsof q472K1Fs+ovpLMoYh4BtgkJNvrZBrDo4s0Y8/TxlVkn//AVZp9AorwxTeVmJvOBbtZQONIFvc LWIlqXW13e4ypzaG2NLZvTLgIcZmuA5qZ/V5ErXhEzhWJ7rM+aS75Tn4rFb4qNrJqR3osmZkn KZNRyPrkCMXcayiPhiGaPrSI4SQ3of07CAtQDbWdz4osKtpnkDhOUcAJFSnsmGOxXC5+vG7ZO 0w4Iy+kV6rK73XXCHHHqJ8+BRgYdT1KMD1l/6R8HmMpUcVXEzsmz2fc++B/9c8OVrYr7J1/Sf bNLEUZldNNWs7dCZqMgfEeHbTeF5s5gAh4GqjsRjItGfEuW4/3kc4KqtgxQurvmie5aNnF3Ux 2yoc/veWJFl9LuVxfawouZiM89HB+MwtbMGPmKNgFwXdP5r0m6A5e6ZBj3h2C7rsFXIrxs4AB U7L0L+qNi4Py0/fzCcGto3zZ/WadJZn6sjdaLL8VpygKIHanvUkfNzgzeAYuIxZ1j4LbRU+Oa eNYEyHRTB7gq07AoqKWH3mZzFqGvIGbnaVIlbTZIdNFHKa3h4BZT7kZ2AnmWgCvI/v6eePlgH NlSeCORvNnMtCA8iWDymWP/a0G8GpFXEHIJO4F1qgXh3rCI+tR9k1Uiia4T9ZV1EVVUAD9O96 PiDu9l/tqaOXaKus+6GTU+VkdVHSZCI3B41OUza4403jJxeaY1xVKhf3hCLdX2IM3DlP1rpEK lqE1/g7cqT5wOg65gkw6Lf72HYWT36eeUXLyX2wlXRECk7nUGMD+HEGL1487hIHmhbNW7qRNZ cggKUUa Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2018-05-06 at 09:42 +0200, Paolo Valente wrote: > > diff --git a/block/bfq-mq-iosched.c b/block/bfq-mq-iosched.c > index 118f319af7c0..6662efe29b69 100644 > --- a/block/bfq-mq-iosched.c > +++ b/block/bfq-mq-iosched.c > @@ -525,8 +525,13 @@ static void bfq_limit_depth(unsigned int op, struct blk_mq_alloc_data *data) > if (unlikely(bfqd->sb_shift != bt->sb.shift)) > bfq_update_depths(bfqd, bt); > > +#if 0 > data->shallow_depth = > bfqd->word_depths[!!bfqd->wr_busy_queues][op_is_sync(op)]; ^^^^^^^^^^^^^ Q: why doesn't the top of this function look like so? --- block/bfq-iosched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -539,7 +539,7 @@ static void bfq_limit_depth(unsigned int struct bfq_data *bfqd = data->q->elevator->elevator_data; struct sbitmap_queue *bt; - if (op_is_sync(op) && !op_is_write(op)) + if (!op_is_write(op)) return; if (data->flags & BLK_MQ_REQ_RESERVED) { It looks a bit odd that these elements exist... +       /* +        * no more than 75% of tags for sync writes (25% extra tags +        * w.r.t. async I/O, to prevent async I/O from starving sync +        * writes) +        */ +       bfqd->word_depths[0][1] = max(((1U<sb_shift) * 3)>>2, 1U); +       /* no more than ~37% of tags for sync writes (~20% extra tags) */ +       bfqd->word_depths[1][1] = max(((1U<sb_shift) * 6)>>4, 1U); ...yet we index via and log a guaranteed zero. -Mike