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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 14BAEC3DA7A for ; Thu, 5 Jan 2023 16:19:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234905AbjAEQTJ (ORCPT ); Thu, 5 Jan 2023 11:19:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55450 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229828AbjAEQTG (ORCPT ); Thu, 5 Jan 2023 11:19:06 -0500 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4B514E42F; Thu, 5 Jan 2023 08:19:05 -0800 (PST) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 59D3F17846; Thu, 5 Jan 2023 16:18:56 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 271F213338; Thu, 5 Jan 2023 16:18:56 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id bxuMCHD4tmM3QwAAMHmgww (envelope-from ); Thu, 05 Jan 2023 16:18:56 +0000 Date: Thu, 5 Jan 2023 17:18:54 +0100 From: Michal =?iso-8859-1?Q?Koutn=FD?= To: Jinke Han Cc: tj@kernel.org, josef@toxicpanda.com, axboe@kernel.dk, cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yinxin.x@bytedance.com, jack@suse.cz Subject: Re: [PATCH v3] blk-throtl: Introduce sync and async queues for blk-throtl Message-ID: <20230105161854.GA1259@blackbody.suse.cz> References: <20221226130505.7186-1-hanjinke.666@bytedance.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="9jxsPFA5p3P2qPhR" Content-Disposition: inline In-Reply-To: <20221226130505.7186-1-hanjinke.666@bytedance.com> User-Agent: Mutt/1.10.1 (2018-07-13) Authentication-Results: smtp-out1.suse.de; none X-Spamd-Result: default: False [-2.20 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.20)[multipart/signed,text/plain]; RCPT_COUNT_SEVEN(0.00)[9]; SIGNED_PGP(-2.00)[]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+,1:+,2:~]; RCVD_COUNT_TWO(0.00)[2]; RCVD_TLS_ALL(0.00)[] Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --9jxsPFA5p3P2qPhR Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Hello Jinke. On Mon, Dec 26, 2022 at 09:05:05PM +0800, Jinke Han wrote: > In our test, fio writes a 100g file in sequential 4k blocksize in > a container with low bps limit configured (wbps=10M). > [...] > At the same time, the operation of saving a small file by vim will be > blocked amolst 140s. Could you please elaborate why is this specific to blk-throtl? I guess similar problem would arise for devices that are "naturally" slow. Then: a) it must have been solved elsewhere in the block layer (but it's broken), b) it should be solved generically in the block layer (thus this is only a partial solution). Alternatively, I imagine your problem could be reduced with corresponding memory limits on IO-constrained cgroups. (The memory limit would increase cgwb's dirty throttling and consequently leaves more IO bandwidth for sync IOs.) Could you describe how the submitted solution compares to memory limiting? > This patch splits bio queue into sync and async queues for blk-throtl > and gives a huge priority to sync write ios. The "huge priority" corresponds to the THROTL_SYNC_FACTOR, right? I'm slightly concerned about the introduction of the magical value. What is the reasoning behind this? (E.g. I'd expect 1:1 could work as well, while 1:4 suggests this is somehow better (empirically?).) Thanks, Michal --9jxsPFA5p3P2qPhR Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- iHUEARYIAB0WIQTrXXag4J0QvXXBmkMkDQmsBEOquQUCY7b4bAAKCRAkDQmsBEOq uQrgAQDs2aA08ChLFwdUU9xtUvTksAkbg4kIOJ6eonBHzYLMmQD9Eku/xsu7q+JO bkt+bgPn6r1by/lxIByZFdvliq70/g0= =VUBu -----END PGP SIGNATURE----- --9jxsPFA5p3P2qPhR--