From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id 1FD816B0038 for ; Mon, 25 Sep 2017 09:53:11 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id 188so16340462pgb.3 for ; Mon, 25 Sep 2017 06:53:11 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id w2si4148628pgb.564.2017.09.25.06.53.09 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 25 Sep 2017 06:53:09 -0700 (PDT) Date: Mon, 25 Sep 2017 15:53:05 +0200 From: Michal Hocko Subject: Re: [PATCHv2] mm: Account pud page tables Message-ID: <20170925135305.ydeeyapav2s36ifj@dhcp22.suse.cz> References: <20170925073913.22628-1-kirill.shutemov@linux.intel.com> <20170925115430.zccesf75c4ysaznb@dhcp22.suse.cz> <20170925130715.kebf5e3xjctpcalp@node.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170925130715.kebf5e3xjctpcalp@node.shutemov.name> Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: "Kirill A. Shutemov" , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vlastimil Babka On Mon 25-09-17 16:07:15, Kirill A. Shutemov wrote: > On Mon, Sep 25, 2017 at 01:54:30PM +0200, Michal Hocko wrote: > > On Mon 25-09-17 10:39:13, Kirill A. Shutemov wrote: > > > On machine with 5-level paging support a process can allocate > > > significant amount of memory and stay unnoticed by oom-killer and > > > memory cgroup. The trick is to allocate a lot of PUD page tables. > > > We don't account PUD page tables, only PMD and PTE. > > > > > > We already addressed the same issue for PMD page tables, see > > > dc6c9a35b66b ("mm: account pmd page tables to the process"). > > > Introduction 5-level paging bring the same issue for PUD page tables. > > > > > > The patch expands accounting to PUD level. > > > > OK, we definitely need this or something like that but I really do not > > like how much code we actually need for each pte level for accounting. > > Do we really need to distinguish each level? Do we have any arch that > > would use a different number of pages to back pte/pmd/pud? > > Looks like we actually do. At least on mips. See PMD_ORDER/PUD_ORDER. Hmm, but then oom_badness does consider them a single page which is wrong. I haven't checked other users. Anyway even if we've had different sizes why cannot we deal with this in callers. They know which level of page table they allocate/free, no? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org