From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C58932BE040 for ; Thu, 31 Jul 2025 10:22:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753957377; cv=none; b=Y6YrAbQJf59qpN5+VzPduJuflRorXZNoZ5vls0e59MWB3gSkSh744lwu/sLHM/KT+hlfTXqkaez99cAXGLtN1fyLKk1cyLMyE+lxnKiugKoYH7Sbyj6tUPxAE+dUfYlpuUKWCwvhK7pRiYxkHNZQ3LyJ5OcyQEyv2MLyR0Le5qk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753957377; c=relaxed/simple; bh=lkkuqC2vambzk9CuZzq6i1jaxoC4n9Munmr9+qei71s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XvBN9MAl0iyN4sgwVHgClEIWFMz/nGyZT6NE2eyal063/cpbVxGcCXffT+f8jfI/XQO06I573pd7GhWixcN/DEHS4TxhfU5aa+StJ9VPJt93I43MD20HsGxCAUyNpx6zUP7qQI2TFIWpiJRzN8BDNge59S3CefNKxVEVZh4xn2E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=HR4sMeYK; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="HR4sMeYK" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1753957374; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fgIENI2JJx96NikmUSVWyLKcBHri0nd2ZYhEFTwOWPM=; b=HR4sMeYK63v+SqoBQTjRAcNulT3H8I8EWDA4nYtIBdVKi4979r7IAL1TXMwG9IpLS8E2Zq JxkyaRCgK1/lIVNW6Ji112qLsoZi7Czd/9hMD8ej6CbvuYCiZBaiI3GA3M4fsYoA8bTSXa 6Ja3NB1eyC/aXxdqxpRb6n9/5gaJLJQ= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-627-lyAZYsORNXKTQrsAMXaCLQ-1; Thu, 31 Jul 2025 06:22:51 -0400 X-MC-Unique: lyAZYsORNXKTQrsAMXaCLQ-1 X-Mimecast-MFC-AGG-ID: lyAZYsORNXKTQrsAMXaCLQ_1753957369 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2C3A9196E073; Thu, 31 Jul 2025 10:22:48 +0000 (UTC) Received: from fedora (unknown [10.72.116.62]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 1AFB91800B6A; Thu, 31 Jul 2025 10:22:39 +0000 (UTC) Date: Thu, 31 Jul 2025 18:22:34 +0800 From: Ming Lei To: Yu Kuai Cc: dlemoal@kernel.org, hare@suse.de, jack@suse.cz, tj@kernel.org, josef@toxicpanda.com, axboe@kernel.dk, cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com, yangerkun@huawei.com, johnny.chenyi@huawei.com, "yukuai (C)" Subject: Re: [PATCH v2 0/5] blk-mq-sched: support request batch dispatching for sq elevator Message-ID: References: <20250730082207.4031744-1-yukuai1@huaweicloud.com> <99e9aa7e-b33c-ce2e-bf0f-0021434690e8@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 On Thu, Jul 31, 2025 at 05:33:24PM +0800, Yu Kuai wrote: > Hi, > > 在 2025/07/31 17:25, Ming Lei 写道: > > On Thu, Jul 31, 2025 at 04:42:10PM +0800, Yu Kuai wrote: > > > Hi, > > > > > > 在 2025/07/31 16:18, Ming Lei 写道: > > > > batch dispatch may hurt io merge performance which is important for > > > > elevator, so please provide test data on real HDD. & SSD., instead of > > > > null_blk only, and it can be perfect if merge sensitive workload > > > > is evaluated. > > > > > > Ok, I'll provide test data on HDD and SSD that I have for now. > > > > > > For the elevator IO merge case, what I have in mind is that we issue > > > small sequential IO one by one with multiple contexts, so that bios > > > won't be merged in plug, and this will require IO issue > IO done, is > > > this case enough? > > > > Long time ago, I investigated one such issue which is triggered in qemu > > workload, but not sure if I can find it now. > > > > Also many scsi devices may easily run into queue busy, then scheduler merge > > starts to work, and it may perform worse if you dispatch more in this > > situation. > > I think we won't dispatch more in this case, on the one hand we will get > budgets first, to make sure never dispatch more than queue_depth; on the OK. > onther hand, in the case hctx->dispatch_busy is set, we still fallback > to the old case to dispatch one at a time; hctx->dispatch_busy is lockless, all request may get dispatched before hctx->dispatch_busy is set. Thanks, Ming