From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f198.google.com (mail-qk0-f198.google.com [209.85.220.198]) by kanga.kvack.org (Postfix) with ESMTP id D73F26B0269 for ; Sun, 1 Jul 2018 22:53:48 -0400 (EDT) Received: by mail-qk0-f198.google.com with SMTP id m15-v6so16614530qkk.9 for ; Sun, 01 Jul 2018 19:53:48 -0700 (PDT) Received: from mx1.redhat.com (mx3-rdu2.redhat.com. [66.187.233.73]) by mx.google.com with ESMTPS id y45-v6si4040448qtb.355.2018.07.01.19.53.48 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 01 Jul 2018 19:53:48 -0700 (PDT) Date: Mon, 2 Jul 2018 10:53:43 +0800 From: Baoquan He Subject: Re: [PATCH v3 1/2] mm/sparse: add sparse_init_nid() Message-ID: <20180702025343.GN3223@MiWiFi-R3L-srv> References: <20180702020417.21281-1-pasha.tatashin@oracle.com> <20180702020417.21281-2-pasha.tatashin@oracle.com> <20180702021121.GL3223@MiWiFi-R3L-srv> <20180702023130.GM3223@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Pavel Tatashin Cc: Steven Sistare , Daniel Jordan , LKML , Andrew Morton , kirill.shutemov@linux.intel.com, Michal Hocko , Linux Memory Management List , dan.j.williams@intel.com, jack@suse.cz, jglisse@redhat.com, Souptick Joarder , gregkh@linuxfoundation.org, Vlastimil Babka , Wei Yang , dave.hansen@intel.com, rientjes@google.com, mingo@kernel.org, osalvador@techadventures.net On 07/01/18 at 10:43pm, Pavel Tatashin wrote: > On Sun, Jul 1, 2018 at 10:31 PM Baoquan He wrote: > > > > On 07/01/18 at 10:18pm, Pavel Tatashin wrote: > > > > Here, I think it might be not right to jump to 'failed' directly if one > > > > section of the node failed to populate memmap. I think the original code > > > > is only skipping the section which memmap failed to populate by marking > > > > it as not present with "ms->section_mem_map = 0". > > > > > > > > > > Hi Baoquan, > > > > > > Thank you for a careful review. This is an intended change compared to > > > the original code. Because we operate per-node now, if we fail to > > > allocate a single section, in this node, it means we also will fail to > > > allocate all the consequent sections in the same node and no need to > > > check them anymore. In the original code we could not simply bailout, > > > because we still might have valid entries in the following nodes. > > > Similarly, sparse_init() will call sparse_init_nid() for the next node > > > even if previous node failed to setup all the memory. > > > > Hmm, say the node we are handling is node5, and there are 100 sections. > > If you allocate memmap for section at one time, you have succeeded to > > handle for the first 99 sections, now the 100th failed, so you will mark > > all sections on node5 as not present. And the allocation failure is only > > for single section memmap allocation case. > > No, unless I am missing something, that's not how code works: > > 463 if (!map) { > 464 pr_err("%s: memory map backing failed. > Some memory will not be available.", > 465 __func__); > 466 pnum_begin = pnum; > 467 goto failed; > 468 } > > 476 failed: > 477 /* We failed to allocate, mark all the following pnums as > not present */ > 478 for_each_present_section_nr(pnum_begin, pnum) { > > We continue from the pnum that failed as we set pnum_begin to pnum, > and mark all the consequent sections as not-present. Ah, yes, I misunderstood it, sorry for that. Then I have only one concern, for vmemmap case, if one section doesn't succeed to populate its memmap, do we need to skip all the remaining sections in that node? > > The only change compared to the original code is that once we found an > empty pnum we stop checking the consequent pnums in this node, as we > know they are empty as well, because there is no more memory in this > node to allocate from. >