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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 1E43EC433DB for ; Wed, 13 Jan 2021 13:02:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B3F2523406 for ; Wed, 13 Jan 2021 13:02:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726680AbhAMNCT (ORCPT ); Wed, 13 Jan 2021 08:02:19 -0500 Received: from mx2.suse.de ([195.135.220.15]:46864 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726262AbhAMNCT (ORCPT ); Wed, 13 Jan 2021 08:02:19 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 0F347B807; Wed, 13 Jan 2021 13:01:36 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id E2CD21E0872; Wed, 13 Jan 2021 14:01:31 +0100 (CET) Date: Wed, 13 Jan 2021 14:01:31 +0100 From: Jan Kara To: Paolo Valente Cc: Jens Axboe , Jan Kara , linux-block Subject: Re: [PATCH] bfq: Fix computation of shallow depth Message-ID: <20210113130131.GD6854@quack2.suse.cz> References: <20201210094433.25491-1-jack@suse.cz> <20210105162141.GA28898@quack2.suse.cz> <238318dd-9103-e4e4-d591-ef7212b86a48@kernel.dk> <78A91DC0-0DC9-41EE-909D-341082CE4DA5@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <78A91DC0-0DC9-41EE-909D-341082CE4DA5@linaro.org> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed 06-01-21 18:02:03, Paolo Valente wrote: > > Il giorno 5 gen 2021, alle ore 17:29, Jens Axboe ha scritto: > > > > On 1/5/21 9:21 AM, Jan Kara wrote: > >> On Thu 10-12-20 10:44:33, Jan Kara wrote: > >>> BFQ computes number of tags it allows to be allocated for each request type > >>> based on tag bitmap. However it uses 1 << bitmap.shift as number of > >>> available tags which is wrong. 'shift' is just an internal bitmap value > >>> containing logarithm of how many bits bitmap uses in each bitmap word. > >>> Thus number of tags allowed for some request types can be far to low. > >>> Use proper bitmap.depth which has the number of tags instead. > >>> > >>> Signed-off-by: Jan Kara > >> > >> Ping Jens? I think it has fallen through the cracks? > > > > More like waiting for Paolo to take a look. Don't mind taking it, and > > I'll do that now, but I do expect him to review any BFQ patches being > > sent out. > > Sorry for the delay Jan. As you know, my priority is currently to > finalize the patches I have developed with your help; and > unfortunately I'm way behind. This is delaying also my review > activity. > > As for your proposal, I remember I found the right parameter rather > empirically. In particular, I seem to remember that the bitmap.depth > parameter did not contain the value I needed, i.e, it did not > contain the total number of tags. But maybe something has changed in > the meantime. At any rate, if bitmap.depth does contain that value, > then your replacement is ok. Yes, bitmap.depth is the total number of tags AFAIK. > If your replacement is ok, then I guess you may want to also fix the > comments above the changes you propose. Oh right, there's one paragraph in the comment that my patch made redundant. I'll send a cleanup. Thanks for noticing. Honza -- Jan Kara SUSE Labs, CR