From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17])
	by smtp.lore.kernel.org (Postfix) with ESMTP id 604A2C433F5
	for <linux-mm@archiver.kernel.org>; Tue, 19 Apr 2022 18:43:45 +0000 (UTC)
Received: by kanga.kvack.org (Postfix)
	id D99AC6B0071; Tue, 19 Apr 2022 14:43:44 -0400 (EDT)
Received: by kanga.kvack.org (Postfix, from userid 40)
	id D494A6B0073; Tue, 19 Apr 2022 14:43:44 -0400 (EDT)
X-Delivered-To: int-list-linux-mm@kvack.org
Received: by kanga.kvack.org (Postfix, from userid 63042)
	id C120A6B0074; Tue, 19 Apr 2022 14:43:44 -0400 (EDT)
X-Delivered-To: linux-mm@kvack.org
Received: from relay.hostedemail.com (relay.a.hostedemail.com [64.99.140.24])
	by kanga.kvack.org (Postfix) with ESMTP id B3CF86B0071
	for <linux-mm@kvack.org>; Tue, 19 Apr 2022 14:43:44 -0400 (EDT)
Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1])
	by unirelay07.hostedemail.com (Postfix) with ESMTP id 791CB226E0
	for <linux-mm@kvack.org>; Tue, 19 Apr 2022 18:43:44 +0000 (UTC)
X-FDA: 79374502368.20.5788784
Received: from out2.migadu.com (out2.migadu.com [188.165.223.204])
	by imf06.hostedemail.com (Postfix) with ESMTP id 0DD66180014
	for <linux-mm@kvack.org>; Tue, 19 Apr 2022 18:43:42 +0000 (UTC)
Date: Tue, 19 Apr 2022 11:43:34 -0700
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1;
	t=1650393821;
	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:
	 in-reply-to:in-reply-to:references:references;
	bh=GFIxKYdHlMseSO1tlyqNC0Z7+2W1DV8pV6RMcsFlSN4=;
	b=J32CmAVJlieNJwRkipeOQWjw09E4O5dhfP8kD80buHhuD7SiitrR8Jm5naMrbQQDIam+2T
	eNj2mvjCXN7eg2zF67LuKwz3ReZjWfv38baEg6aS2TZo3McQQ2ymVLj7LutgD14PNTtDlV
	RqXuecTfdJigZkk2ZgjXT5HvBG6tLqM=
X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers.
From: Roman Gushchin <roman.gushchin@linux.dev>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, Dave Chinner <dchinner@redhat.com>,
	linux-kernel@vger.kernel.org, Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	Shakeel Butt <shakeelb@google.com>, Yang Shi <shy828301@gmail.com>
Subject: Re: [PATCH rfc 0/5] mm: introduce shrinker sysfs interface
Message-ID: <Yl8C1nDr2jUnFn3V@carbon>
References: <20220416002756.4087977-1-roman.gushchin@linux.dev>
 <20220418212709.42f2ba15e00999bb57086b27@linux-foundation.org>
 <Yl727M1Dxm+vC/R1@carbon>
 <20220419112549.a42f1d86b025112d3a3aaf8c@linux-foundation.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220419112549.a42f1d86b025112d3a3aaf8c@linux-foundation.org>
X-Migadu-Flow: FLOW_OUT
X-Migadu-Auth-User: linux.dev
X-Rspam-User: 
X-Rspamd-Server: rspam03
X-Rspamd-Queue-Id: 0DD66180014
X-Stat-Signature: y1x64j5hfc1k69qm7h4i1c7ndxfz18et
Authentication-Results: imf06.hostedemail.com;
	dkim=pass header.d=linux.dev header.s=key1 header.b=J32CmAVJ;
	dmarc=pass (policy=none) header.from=linux.dev;
	spf=pass (imf06.hostedemail.com: domain of roman.gushchin@linux.dev designates 188.165.223.204 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev
X-HE-Tag: 1650393822-78656
X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4
Sender: owner-linux-mm@kvack.org
Precedence: bulk
X-Loop: owner-majordomo@kvack.org
List-ID: <linux-mm.kvack.org>

On Tue, Apr 19, 2022 at 11:25:49AM -0700, Andrew Morton wrote:
> On Tue, 19 Apr 2022 10:52:44 -0700 Roman Gushchin <roman.gushchin@linux.dev> wrote:
> 
> > > Unclear.  At the end of what output?
> > 
> > This is how it looks like when the output is too long:
> > 
> > [root@eth50-1 sb-btrfs-24]# cat count_memcg
> > 1 226
> > 20 96
> > 53 811
> > 2429 2
> > 218 13
> > 581 29
> > 911 124
> > 1010 3
> > 1043 1
> > 1076 1
> > 1241 60
> > 1274 7
> > 1307 39
> > 1340 3
> > 1406 14
> > 1439 63
> > 1472 54
> > 1505 8
> > 1538 1
> > 1571 6
> > 1604 39
> > 1637 9
> > 1670 8
> > 1703 4
> > 1736 1094
> > 1802 2
> > 1868 2
> > 1901 52
> > 1934 592
> > 1967 32
> > 			< CUT >
> > 18797 1
> > 18830 1
> 
> We do that in-kernel?  Why?  That just makes parsers harder to write?
> If someone has issues then direct them at /usr/bin/less?

It comes from the sysfs limitation: it expects that the output should fit
into the PAGE_SIZE. If the number of cgroups (and nodes) is large, it's not
always possible. In theory something like seq_file API should be used, but
Idk how hard it's to mix it with the sysfs/debugfs API. I'll try to figure
this out.