From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH v3 1/2] mm, proc: Fix region lost in /proc/self/smaps Date: Thu, 29 Sep 2016 15:42:48 +0200 Message-ID: <20160929134248.GI408@dhcp22.suse.cz> References: <1474636354-25573-1-git-send-email-robert.hu@intel.com> <20160923135635.GB28734@redhat.com> <20160923145301.GU4478@dhcp22.suse.cz> <20160923155351.GA1584@redhat.com> <20160926084616.GA28550@dhcp22.suse.cz> <1475154880.16655.9.camel@vmm.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Oleg Nesterov , pbonzini@redhat.com, akpm@linux-foundation.org, dan.j.williams@intel.com, dave.hansen@intel.com, guangrong.xiao@linux.intel.com, gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, stefanha@redhat.com, yuhuang@redhat.com, linux-mm@kvack.org, ross.zwisler@linux.intel.com To: robert.hu@intel.com Return-path: Received: from mail-wm0-f65.google.com ([74.125.82.65]:33449 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750700AbcI2NnE (ORCPT ); Thu, 29 Sep 2016 09:43:04 -0400 Content-Disposition: inline In-Reply-To: <1475154880.16655.9.camel@vmm.sh.intel.com> Sender: kvm-owner@vger.kernel.org List-ID: On Thu 29-09-16 21:14:40, Robert Hu wrote: > On Mon, 2016-09-26 at 10:46 +0200, Michal Hocko wrote: > > On Fri 23-09-16 17:53:51, Oleg Nesterov wrote: > > > On 09/23, Michal Hocko wrote: > > > > > > > > On Fri 23-09-16 15:56:36, Oleg Nesterov wrote: > > > > > > > > > > I think we can simplify this patch. And imo make it better. How about > > > > > > > > it is certainly less subtle because it doesn't report "sub-vmas". > > > > > > > > > if (last_addr) { > > > > > vma = find_vma(mm, last_addr - 1); > > > > > if (vma && vma->vm_start <= last_addr) > > > > > vma = m_next_vma(priv, vma); > > > > > if (vma) > > > > > return vma; > > > > > } > > > > > > > > we would still miss a VMA if the last one got shrunk/split > > > > > > Not sure I understand what you mean... If the last one was split > > > we probably should not report the new vma. > > > > Right, VMA split is less of a problem. I meant to say that if the > > last_vma->vm_end got lower for whatever reason then we could miss a VMA > > right after. We actually might want to display such a VMA because it > > could be a completely new one. We just do not know whether it is a > > former split with enlarged VMA or a completely new one > > > > [ old VMA ] Hole [ VMA ] > > [ old VMA ][ New VMa ] [ VMA ] > > This is indeed possible. But I see this is like the last_vma enlargement > case. I suggest we accept such missing, as we accept the enlargement > part of last_vma is not printed. > > How about we set such target: 0) consistent output can be achieved only in the single read call > 1) no duplicate print; 2) no old vma > missing (unless it's unmapped); 3) monotonic printing. > We accept those newly added/changed parts between 2 partial reads is not > printed. OK -- Michal Hocko SUSE Labs