From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.9 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793624595; b=j+k+Z4CHE3UleuA59JR07mHjtH5SQ+fCgzSCRub8/ZYPDclD/WfTNY3bR7F+PHC+IKgt TG1dJPNvDrz0gdCZmMBjiEJdRHPH9sj+fgy4aQEbHa2X60DSEa+7mExvLPtN+g+KkLI4R 5ce3qKV+uZ/mPqhpvfr8FyDYPnRAHqTkHhLeJNk0MYTItih0zws1Xi87fTV0D6MOHdf+I bdHUK+1LOnMnU8U/vomFffq2e6n3XFIr2oaCt0+xH8rMxBvy7ibusViVQ5GggO48niSwc 0aLal1KuZky7y70usvNedW3fp2Pgsv2YoN5TN40A9xin26XkXGZ1iGz4tR1j27XStwA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793624595; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:Message-ID:Date:MIME-Version:User-Agent: Cc:Subject:To:References:From:In-Reply-To:Content-Type: Content-Transfer-Encoding; bh=FXUqkUNHxYE2NGpJQs5al5RvPwIjMfRnSOyTuQqz9ps=; b=YL7aFR0ihlp7R5RwzW13clnr/Ue+MDlTJLYI3HuveY+LETvi5w6g93ZN9m/fproP7Abx M1QL6ohk9cwtoCwFfcdpwoBwq2EPBluGpPF0ywFvFlpFaH8BY3+ClVbPNzuexHOclcPNw o+jnbJILBvj/aaRPbdsbyAJV5FoUQ5t680u8pvmCEMrGDGZfl8TTKNQ4vIc46KE03QUXv 3RSAd4tTV7zKD5TK/7WuWlY+O9EaRp5rTYtHY5Zvt4bkgbrNG5GJy6zHD4MWZ3FcaNx22 /6RWDQh7hWwU/pGr/k45fNN/RrIufI538CEsK2lp6JWFhUoyrUjonB1P2AvPIYMCtJg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=GqIPqxUf; arc=none smtp.remote-ip=95.215.58.9 Received: from mta1.migadu.com (out-9.mta1.migadu.com [95.215.58.9]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9BA0560A2622 for ; Mon, 2 Nov 2026 13:03:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 9BA0560A2622 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=GqIPqxUf X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=ReST3cWLqWrD/t1sA1J8bJ67KuQOqTddHpAzRisO018=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793624592; v=1; x=1794229392; b=GqIPqxUfLfW7mSUNjHodoC2JNe5t6hFUMQgYL22fCM2tZQyOnaGgGP3RC6UReR655Qj/SKsD BzAoJI75o5CvVAA+tJBk0Lsb5rKxw5yZXAmUpWosbPLWvracM6vQOrbqjbAh8DiGzvDD6gHZxRS ZS2fMbo2RVsmx5OnsnjK8eNA= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 2247600f0cc60053; Mon, 02 Nov 2026 13:03:12 +0000 X-Mizu-Trace-ID: 2247600f0cc60053 X-Migadu-Flow: FLOW_OUT Message-ID: <32e80536-64e4-4ae3-a7da-4a37ed415f0a@linux.dev> Date: Mon, 2 Nov 2026 21:03:05 +0800 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: cui.tao@linux.dev, Johannes Weiner , Michal Hocko , Shakeel Butt , muchun.song@linux.dev, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Tao Cui Subject: Re: [RFC PATCH 0/3] mm, memcg: isolate deprecated v1 state from struct mem_cgroup To: Roman Gushchin References: <0BEF7489-16EC-44EE-847B-A6AA380BE11F@linux.dev> From: Tao Cui In-Reply-To: <0BEF7489-16EC-44EE-847B-A6AA380BE11F@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Roman, 在 2026/10/30 14:05, Roman Gushchin 写道: > I believe we want to delete this code sooner than later, why would we rewrite it before that? > My assumption was that v1 would still be maintained for some time before its eventual removal, and the goal was to reduce the coupling between the remaining v1 code and the shared core structures during that period, rather than to rewrite the implementation for its own sake. If the expectation is that the remaining v1 implementation will be removed in the near future, then I agree this work becomes much harder to justify. Am I being too optimistic about how long the remaining v1 code is expected to stay around? Thanks, Tao >> On Oct 29, 2026, at 10:40 PM, Tao Cui wrote: >> >> Hi Johannes, Shakeel, Michal, >> >>> 在 2026/9/19 00:24, Johannes Weiner 写道: >>>> On Fri, Sep 18, 2026 at 11:41:09AM +0200, Michal Hocko wrote: >>>> On Thu 17-09-26 13:26:40, Shakeel Butt wrote: >>>>> On Wed, Sep 16, 2026 at 08:57:34PM +0800, Tao Cui wrote: >>>>>> From: Tao Cui >>>>>> >>>>>> The legacy cgroup v1 memory controller has already been moved out of >>>>>> the shared implementation at the file level (mm/memcontrol-v1.c) and at >>>>>> the Kconfig level (CONFIG_MEMCG_V1, default n since 6.11). Its >>>>>> per-cgroup state, however, still sits as individual members inside >>>>>> struct mem_cgroup, guarded by #ifdefs. >>>>>> >>>>>> This series isolates the deprecated implementation from the shared hot >>>>>> structure: all v1-only members are grouped into a dedicated >>>>>> struct mem_cgroup_v1, and every access goes through memcg->v1.X. >>>>>> >>>>>> With this in place the v1 implementation is self-contained: its >>>>>> interface in mm/memcontrol-v1.c, its state in struct mem_cgroup_v1, and >>>>>> its eventual removal becomes a localized deletion of this struct >>>>>> together with mm/memcontrol-v1.c, instead of unwinding >>>>>> ifdef-scattered members across the shared header. >>>>> >>>>> Sorry I don't see any benefit of this code churn. The code is already behind >>>>> config. What exactly this code churn is giving us? >>>> >>>> The only arguable upside is that this would make it ever so slightly >>>> easier to track v1 specific stuff (once that s@v1@memcg1@ or similar). >>> >>> I had the same thought. It's kiiind of nice to see which members are >>> completely specific to memcg1. >>> >>>> I am not convinced this is sufficient to justify the churn either. >>> >>> IMO it helps that it's mostly in memcontrol-v1.c where the chances of >>> interfering with other work are pretty slim. >>> >>> The patch 1 + patch 2 split is a bit bothersome: indenting everything >>> into a union, only to then move it out in the next patch. >>> >>> Tao, if you folded these two patches to make it one clean extraction >>> and changed over the sites at the same time, I would probably lean >>> supportive on this. >> >> Sorry for the late reply. >> >> Thanks for the feedback. Looking back, I think Johannes' point about >> the patch split is fair. I split the first two patches to keep the >> initial step semantically neutral, but it also made the series look >> like churn for the sake of churn. >> >> I'll fold the first two patches into a single extraction in the next >> revision. That should present the change more directly and hopefully >> make it easier to judge whether the resulting boundary is worthwhile. >> >> Thanks, >> Tao >> >>