From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 149B523504B; Tue, 3 Mar 2026 17:46:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772560008; cv=none; b=mafZ06LzQ0shQMCHBAxLeofvT7FmazJNBdUjs2ewCSvbpiveWJgGzuzHBcj/SZOagu3TRfwRMdHjfvBF2ab4udznwC68KQhmlVq0n7Ck5fX52C2kG+aydCiqIWrUXo6lnAU61xZTOTpOBA6XVdvb/OFIbJjzjOERN61bsR1nhWw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772560008; c=relaxed/simple; bh=pkZZGED7G2fAh6j3YIUUz6F68t5YZV31NNoav7BnR5c=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=iAWKLiGbCTGCp1gafjW9z6LwJZXjz+sfZLf96WzJNb2VMfdox4MmzXH97kBaF/MwgrJ+uCTsR6B8+2TemK2k/gxyH72ejBlFQ/mxi9E/iLeRfZlPD080IF4rtTTzWaWJ1GCdiLlbT7GQgJDnoOtl4MiTddLLCjXpWZdhFiCocf8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cHPXDNMN; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cHPXDNMN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 97C8DC116C6; Tue, 3 Mar 2026 17:46:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772560007; bh=pkZZGED7G2fAh6j3YIUUz6F68t5YZV31NNoav7BnR5c=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cHPXDNMNz/mef/W/uZkh+FjjEBrvxDpUYyNbmnwRJwzFuyt8+XNwPjFnQbd9kCdPE ShEK3kp5k2jhW0r3s/f53116GhH757HsRtknsGldVldwZMJ3jkL7XE3QLH52Ynh+1Z r3pEvCxYBwt1xLLRwq45TNGnLPhgvVS2AZhYWSgaOKPWJ8lijSVMR4HLg733dz9NNw EqbAdo2UqHLcnJZRmKujo3o9mFjSwWMj7n72509Q8nl1I3PIloxsgdYomjjErcqM8A s3aEWqUmWZd8E28hCVleRF1FHsB1oSACBEnutGuYy1WOm9qp5ih/K1aEWmoW1YttB4 GRqvzTBjE8PhA== Date: Tue, 3 Mar 2026 07:46:46 -1000 From: Tejun Heo To: Breno Leitao Cc: Jens Axboe , Josef Bacik , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, thevlad@meta.com, kernel-team@meta.com, Michal =?iso-8859-1?Q?Koutn=FD?= Subject: Re: [PATCH v2] blk-cgroup: always display debug stats in io.stat Message-ID: References: <20260303-blk_cgroup_debug_stats-v2-1-196c713cb762@debian.org> 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=us-ascii Content-Disposition: inline In-Reply-To: <20260303-blk_cgroup_debug_stats-v2-1-196c713cb762@debian.org> Hello, On Tue, Mar 03, 2026 at 06:11:15AM -0800, Breno Leitao wrote: > Remove the blkcg_debug_stats toggle and always display detailed > statistics in the cgroup io.stat file. This includes use_delay and > delay_nsec information, cost.wait/cost.indebt/cost.indelay for iocost, > and latency statistics for iolatency. > > The stats are already being collected regardless of the toggle, so > gating their display provides no real benefit. Additionally, blk-cgroup The reason for gating is that these are more internal implementation details and might change in the future. > has not been modularized since commit 32e380aedc3de ("blkcg: make > CONFIG_BLK_CGROUP bool"), making the module parameter a historical > artifact. Readers of the nested-keys format should be able to handle > additional fields. I'm not sure what the above para means. Module param works just fine for built-in modules on both boot command line and through sysfs. > Before (without blkcg_debug_stats enabled): > 253:0 rbytes=6273024 wbytes=0 rios=20 wios=0 dbytes=0 dios=0 cost.usage=0 > > After: > 253:0 rbytes=6273024 wbytes=0 rios=20 wios=0 dbytes=0 dios=0 cost.usage=0 cost.wait=0 cost.indebt=0 cost.indelay=0 Given that they haven't changed for a long time, maybe it's okay to expose them by default, but why? This is something which can be toggled on easily at any time. What's the benefit of exposing these extra numbers which probably don't mean much for most people? Thanks. -- tejun