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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 96A3FC4332F for ; Mon, 18 Oct 2021 08:06:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7C67E61050 for ; Mon, 18 Oct 2021 08:06:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230512AbhJRIIT (ORCPT ); Mon, 18 Oct 2021 04:08:19 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:3993 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230472AbhJRIIS (ORCPT ); Mon, 18 Oct 2021 04:08:18 -0400 Received: from fraeml715-chm.china.huawei.com (unknown [172.18.147.206]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4HXq9B2gjpz67Mww; Mon, 18 Oct 2021 16:02:22 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml715-chm.china.huawei.com (10.206.15.34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.15; Mon, 18 Oct 2021 10:06:06 +0200 Received: from [10.47.85.98] (10.47.85.98) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.15; Mon, 18 Oct 2021 09:06:05 +0100 Subject: Re: [PATCH] blk-mq: Fix blk_mq_tagset_busy_iter() for shared tags From: John Garry To: Ming Lei CC: "axboe@kernel.dk" , "linux-block@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "kashyap.desai@broadcom.com" , "hare@suse.de" References: <1634114459-143003-1-git-send-email-john.garry@huawei.com> <79266509-f327-9de3-d22e-0e9fe00387ee@huawei.com> <9f3c4d57-6b77-5345-0d4c-275962214b2a@huawei.com> <7e142559-1c96-8d84-081a-378c1f6d1306@huawei.com> Message-ID: <1065f517-c94b-5a47-34f6-52015b3ef907@huawei.com> Date: Mon, 18 Oct 2021 09:08:57 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <7e142559-1c96-8d84-081a-378c1f6d1306@huawei.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.47.85.98] X-ClientProxiedBy: lhreml718-chm.china.huawei.com (10.201.108.69) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 13/10/2021 16:13, John Garry wrote: >> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c >> index 72a2724a4eee..2a2ad6dfcc33 100644 >> --- a/block/blk-mq-tag.c >> +++ b/block/blk-mq-tag.c >> @@ -232,8 +232,9 @@ static bool bt_iter(struct sbitmap *bitmap, >> unsigned int bitnr, void *data) >>       if (!rq) >>           return true; >> -    if (rq->q == hctx->queue && rq->mq_hctx == hctx) >> -        ret = iter_data->fn(hctx, rq, iter_data->data, reserved); >> +    if (rq->q == hctx->queue && (rq->mq_hctx == hctx || >> +                blk_mq_is_shared_tags(hctx->flags))) >> +        ret = iter_data->fn(rq->mq_hctx, rq, iter_data->data, reserved); >>       blk_mq_put_rq_ref(rq); >>       return ret; >>   } >> @@ -460,6 +461,9 @@ void blk_mq_queue_tag_busy_iter(struct >> request_queue *q, busy_iter_fn *fn, >>           if (tags->nr_reserved_tags) >>               bt_for_each(hctx, &tags->breserved_tags, fn, priv, true); >>           bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false); >> + >> +        if (blk_mq_is_shared_tags(hctx->flags)) >> +            break; >>       } >>       blk_queue_exit(q); >>   } >> > > I suppose that is ok, and means that we iter once. > > However, I have to ask, where is the big user of > blk_mq_queue_tag_busy_iter() coming from? I saw this from Kashyap's mail: > > > 1.31%     1.31%  kworker/57:1H-k  [kernel.vmlinux] > >       native_queued_spin_lock_slowpath > >       ret_from_fork > >       kthread > >       worker_thread > >       process_one_work > >       blk_mq_timeout_work > >       blk_mq_queue_tag_busy_iter > >       bt_iter > >       blk_mq_find_and_get_req > >       _raw_spin_lock_irqsave > >       native_queued_spin_lock_slowpath > > How or why blk_mq_timeout_work()? Just some update: I tried hisi_sas with 10x SAS SSDs, megaraid sas with 1x SATA HDD (that's all I have), and null blk with lots of devices, and I still can't see high usage of blk_mq_queue_tag_busy_iter(). So how about we get this patch processed (to fix blk_mq_tagset_busy_iter()), as it is independent of blk_mq_queue_tag_busy_iter()? And then wait for some update or some more info from Kashyap regarding blk_mq_queue_tag_busy_iter() Thanks, John