From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1756231AbcDGMvu (ORCPT <rfc822;w@1wt.eu>);
	Thu, 7 Apr 2016 08:51:50 -0400
Received: from mail-wm0-f67.google.com ([74.125.82.67]:34787 "EHLO
	mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1755740AbcDGMvs (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 7 Apr 2016 08:51:48 -0400
Date: Thu, 7 Apr 2016 14:51:45 +0200
From: Michal Hocko <mhocko@kernel.org>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Nikolay Borisov <kernel@kyup.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch v2] mm, hugetlb_cgroup: round limit_in_bytes down to
 hugepage size
Message-ID: <20160407125145.GD32755@dhcp22.suse.cz>
References: <alpine.DEB.2.10.1604051824320.32718@chino.kir.corp.google.com>
 <5704BA37.2080508@kyup.com>
 <5704BBBF.8040302@kyup.com>
 <alpine.DEB.2.10.1604061510040.10401@chino.kir.corp.google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.10.1604061510040.10401@chino.kir.corp.google.com>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed 06-04-16 15:10:23, David Rientjes wrote:
[...]
> +static void hugetlb_cgroup_init(struct hugetlb_cgroup *h_cgroup,
> +				struct hugetlb_cgroup *parent_h_cgroup)
> +{
> +	int idx;
> +
> +	for (idx = 0; idx < HUGE_MAX_HSTATE; idx++) {
> +		struct page_counter *counter = &h_cgroup->hugepage[idx];
> +		struct page_counter *parent = NULL;
> +		unsigned long limit;
> +		int ret;
> +
> +		if (parent_h_cgroup)
> +			parent = &parent_h_cgroup->hugepage[idx];
> +		page_counter_init(counter, parent);
> +
> +		limit = round_down(PAGE_COUNTER_MAX,
> +				   1 << huge_page_order(&hstates[idx]));
> +		ret = page_counter_limit(counter, limit);
> +		VM_BUG_ON(ret);
> +	}
> +}

I fail to see the point for this. Why would want to round down
PAGE_COUNTER_MAX? It will never make a real difference. Or am I missing
something?
-- 
Michal Hocko
SUSE Labs