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=-8.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 0A658C43461 for ; Thu, 10 Sep 2020 17:18:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9A1FB214F1 for ; Thu, 10 Sep 2020 17:18:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Vqh1YREu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726961AbgIJRQe (ORCPT ); Thu, 10 Sep 2020 13:16:34 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:43671 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726109AbgIJRP7 (ORCPT ); Thu, 10 Sep 2020 13:15:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1599758152; 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: in-reply-to:in-reply-to:references:references; bh=V5RVkZoHNNgO8iRkts2uQucFzF0PqLciDsVyoi9bgfc=; b=Vqh1YREuDnGDHlUQI8FhTpJBgjFTUerDdqwuKT1SuiG0skGf/NIcWSsNHz/GGineP6h9JZ cYFtj4W+OkQUSJwbk9gUdpHz7YPzikC8puh+hmMlxBa+69LnSIIHOKu5teGf/hc3lZG568 18Gu9RDSAG38TVjI0UuMb1HP7sV4uqk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-250-HnAUMfNAM0OMvyN4RsRhjA-1; Thu, 10 Sep 2020 13:15:48 -0400 X-MC-Unique: HnAUMfNAM0OMvyN4RsRhjA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D7CFB802B72; Thu, 10 Sep 2020 17:15:45 +0000 (UTC) Received: from localhost (unknown [10.18.25.174]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 061BB60BFA; Thu, 10 Sep 2020 17:15:42 +0000 (UTC) Date: Thu, 10 Sep 2020 13:15:41 -0400 From: Mike Snitzer To: Christoph Hellwig Cc: Jens Axboe , linux-block@vger.kernel.org, martin.petersen@oracle.com, Hans de Goede , Song Liu , Richard Weinberger , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, Minchan Kim , dm-devel@redhat.com, linux-mtd@lists.infradead.org, linux-mm@kvack.org, drbd-dev@tron.linbit.com, cgroups@vger.kernel.org Subject: Re: [PATCH 06/14] block: lift setting the readahead size into the block layer Message-ID: <20200910171541.GB21919@redhat.com> References: <20200726150333.305527-1-hch@lst.de> <20200726150333.305527-7-hch@lst.de> <20200826220737.GA25613@redhat.com> <20200902151144.GA1738@lst.de> <20200902162007.GB5513@redhat.com> <20200910092813.GA27229@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200910092813.GA27229@lst.de> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Sep 10 2020 at 5:28am -0400, Christoph Hellwig wrote: > On Wed, Sep 02, 2020 at 12:20:07PM -0400, Mike Snitzer wrote: > > On Wed, Sep 02 2020 at 11:11am -0400, > > Christoph Hellwig wrote: > > > > > On Wed, Aug 26, 2020 at 06:07:38PM -0400, Mike Snitzer wrote: > > > > On Sun, Jul 26 2020 at 11:03am -0400, > > > > Christoph Hellwig wrote: > > > > > > > > > Drivers shouldn't really mess with the readahead size, as that is a VM > > > > > concept. Instead set it based on the optimal I/O size by lifting the > > > > > algorithm from the md driver when registering the disk. Also set > > > > > bdi->io_pages there as well by applying the same scheme based on > > > > > max_sectors. > > > > > > > > > > Signed-off-by: Christoph Hellwig > > > > > --- > > > > > block/blk-settings.c | 5 ++--- > > > > > block/blk-sysfs.c | 1 - > > > > > block/genhd.c | 13 +++++++++++-- > > > > > drivers/block/aoe/aoeblk.c | 2 -- > > > > > drivers/block/drbd/drbd_nl.c | 12 +----------- > > > > > drivers/md/bcache/super.c | 4 ---- > > > > > drivers/md/dm-table.c | 3 --- > > > > > drivers/md/raid0.c | 16 ---------------- > > > > > drivers/md/raid10.c | 24 +----------------------- > > > > > drivers/md/raid5.c | 13 +------------ > > > > > 10 files changed, 16 insertions(+), 77 deletions(-) > > > > > > > > > > > > In general these changes need a solid audit relative to stacking > > > > drivers. That is, the limits stacking methods (blk_stack_limits) > > > > vs lower level allocation methods (__device_add_disk). > > > > > > > > You optimized for lowlevel __device_add_disk establishing the bdi's > > > > ra_pages and io_pages. That is at the beginning of disk allocation, > > > > well before any build up of stacking driver's queue_io_opt() -- which > > > > was previously done in disk_stack_limits or driver specific methods > > > > (e.g. dm_table_set_restrictions) that are called _after_ all the limits > > > > stacking occurs. > > > > > > > > By inverting the setting of the bdi's ra_pages and io_pages to be done > > > > so early in __device_add_disk it'll break properly setting these values > > > > for at least DM afaict. > > > > > > ra_pages never got inherited by stacking drivers, check it by modifying > > > it on an underlying device and then creating a trivial dm or md one. > > > > Sure, not saying that it did. But if the goal is to set ra_pages based > > on io_opt then to do that correctly on stacking drivers it must be done > > in terms of limits stacking right? Or at least done at a location that > > is after the limits stacking has occurred? So should DM just open-code > > setting ra_pages like it did for io_pages? > > > > Because setting ra_pages in __device_add_disk() is way too early for DM > > -- given it uses device_add_disk_no_queue_reg via add_disk_no_queue_reg > > at DM device creation (before stacking all underlying devices' limits). > > I'll move it to blk_register_queue, which should work just fine. That'll work for initial DM table load as part of DM device creation (dm_setup_md_queue). But it won't account for DM table reloads that might change underlying devices on a live DM device (done using __bind). Both dm_setup_md_queue() and __bind() call dm_table_set_restrictions() to set/update queue_limits. It feels like __bind() will need to call a new block helper to set/update parts of queue_limits (e.g. ra_pages and io_pages). Any chance you're open to factoring out that block function as an exported symbol for use by blk_register_queue() and code like DM's __bind()? Thanks, Mike