From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 2ABBE176AB1 for ; Fri, 12 Jul 2024 17:10:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720804248; cv=none; b=Ia6sX3Il0oQLmuc1ndHiT3ejpjbeNwhUYsHSngja56TPI0XeMWvhFcFOLRtSL/57DrH81UTNc/Xz+cliibAW3UkZUlgjm4EkOSNY6BzsHkYwtUmhrwV4CbjqnG0Z2L7IdA/s2VdeQz4yo1UN+sp0cGLUV1FuWl25OP/msNbF3AY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720804248; c=relaxed/simple; bh=QPbldaZLRVQw71mtTkMjBKj0haUUdISrLOQxYOJKFgw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rVPVTZC3YobEJ2MSd+1TFuFFsQsWamyXkMR1aUVESq7AWlsFqQLLShqpCq32G6mnhR8pcpw8mZ0H5H1D3fg9x9BDLWihaHrBsv5aFOS6sWQrx9sKyXDEB379A6CXJd4psK1YuxEPxrJyLvsXRNuftuIYOYW3ZQ+zFMP1KQHVBas= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=ipjuiIJP; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ipjuiIJP" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1720804246; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bnm3ivYBPn9ycwUjzHL/j+hS87OKKBuD3Bec1gFTGWo=; b=ipjuiIJPOsDJv1/zAIi1XKuYeRk4LC/JRPKjckRCwVHjk/QfZBdf5LNPfbpkPVdZZThNrs pfQ/hAKLbHE8BcSrZm5Ap65CL75A6XwWESksZzza8UO43P5wqsVCWHg9MDQ/ecyPiJ5vqE 4DWpOj7mCGMaPE7SrxIyTYwU0w6XIYw= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-691-oogQPAjpN5SBGdDFLTZiSA-1; Fri, 12 Jul 2024 13:10:41 -0400 X-MC-Unique: oogQPAjpN5SBGdDFLTZiSA-1 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E43AF195608B; Fri, 12 Jul 2024 17:10:38 +0000 (UTC) Received: from [10.22.17.116] (unknown [10.22.17.116]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 259321955F40; Fri, 12 Jul 2024 17:10:36 +0000 (UTC) Message-ID: <48802fec-0563-429b-95b2-571862ffff18@redhat.com> Date: Fri, 12 Jul 2024 13:10:36 -0400 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/2] cgroup: Show # of subsystem CSSes in cgroup.stat To: Johannes Weiner Cc: Tejun Heo , Zefan Li , Jonathan Corbet , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Kamalesh Babulal , Roman Gushchin References: <20240711134927.GB456706@cmpxchg.org> <4e1078d6-6970-4eea-8f73-56a3815794b5@redhat.com> <76e70789-986a-44c2-bfdc-d636f425e5ae@redhat.com> <20240711195946.GA1094169@cmpxchg.org> <20240712162920.GA1321673@cmpxchg.org> Content-Language: en-US From: Waiman Long In-Reply-To: <20240712162920.GA1321673@cmpxchg.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 On 7/12/24 12:29, Johannes Weiner wrote: > On Thu, Jul 11, 2024 at 05:00:41PM -0400, Waiman Long wrote: >> On 7/11/24 15:59, Johannes Weiner wrote: >>> On Thu, Jul 11, 2024 at 03:13:12PM -0400, Waiman Long wrote: >>>> On 7/11/24 14:59, Tejun Heo wrote: >>>>> On Thu, Jul 11, 2024 at 02:51:38PM -0400, Waiman Long wrote: >>>>>> On 7/11/24 14:44, Tejun Heo wrote: >>>>>>> Hello, >>>>>>> >>>>>>> On Thu, Jul 11, 2024 at 01:39:38PM -0400, Waiman Long wrote: >>>>>>>> On 7/11/24 13:18, Tejun Heo wrote: >>>>>>> ... >>>>>>>> Currently, I use the for_each_css() macro for iteration. If you mean >>>>>>>> displaying all the possible cgroup subsystems even if they are not enabled >>>>>>>> for the current cgroup, I will have to manually do the iteration. >>>>>>> Just wrapping it with for_each_subsys() should do, no? for_each_css() won't >>>>>>> iterate anything if css doesn't exist for the cgroup. >>>>>> OK, I wasn't sure if you were asking to list all the possible cgroup v2 >>>>>> cgroup subsystems even if they weren't enabled in the current cgroup. >>>>>> Apparently, that is the case. I prefer it that way too. >>>>> Yeah, I think listing all is better. If the list corresponded directly to >>>>> cgroup.controllers, it may make sense to only show enabled ones but we can >>>>> have dying ones and implicitly enabled memory and so on, so I think it'd be >>>>> cleaner to just list them all. >>>> That will means cgroup subsystems that are seldomly used like rdma, misc >>>> or even hugetlb will always be shown in all the cgroup.stat output. I >>>> actually prefer just showing those that are enabled. As for dying memory >>>> cgroups, they will only be shown in its online ancestors. We currently >>>> don't know how many level down are each of the dying ones. >>> It seems odd to me to not show dead ones after a cgroup has disabled >>> the controller again. They still consume memory, after all, and so >>> continue to be property of that cgroup afterwards. >>> >>> Instead of doing for_each_css(), would it make more sense to have >>> >>> struct cgroup { >>> ... >>> int nr_dying_subsys[CGROUP_SUBSYS_COUNT]; >> What exactly does new this array for? > For keeping the counts. Instead of inside the css. > > AFAICS, with your current patch, if somebody were to disable the > controller in cgroup.subtree_control, it would offline the css at that > level, become unreachable from cgroup->subsys[], and you'd lose > remaining counts of dead css that are still associated with that > cgroup. Re-enabling the controller would create a new css with new > descendant counts, and now the reported numbers are actively misleading. > > That seems undesirable. > > If you track the counts in the cgroup itself, then cgroup.stat would > reliably show the total counts of dead controllers that are associated > with the subtree, even after disabling or toggling controllers. > > The hooks in online, offline, release should be the same, just update > css->cgroup->nr_dying_subsys[id] instead of css->nr_dying_descendants. That does make sense. Thank for the suggestion. I will update the patch accordingly. Cheers, Longman