From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f198.google.com (mail-wr0-f198.google.com [209.85.128.198]) by kanga.kvack.org (Postfix) with ESMTP id 4AA162803C7 for ; Wed, 10 May 2017 02:51:23 -0400 (EDT) Received: by mail-wr0-f198.google.com with SMTP id z88so5542961wrc.9 for ; Tue, 09 May 2017 23:51:23 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id d188si3295593wmc.0.2017.05.09.23.51.21 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 09 May 2017 23:51:22 -0700 (PDT) Subject: Re: [PATCH v2] mm: fix the memory leak after collapsing the huge page fails References: <1494327305-835-1-git-send-email-zhongjiang@huawei.com> <442638e9-d6db-2f1c-e260-9290d7524f1d@suse.cz> <5911B40D.2020007@huawei.com> <0bca4592-efa5-deba-0369-19beacfd2a63@suse.cz> <5911C9F9.3020802@huawei.com> From: Vlastimil Babka Message-ID: <6810ea54-faed-fcc1-7751-ff91fa3f9d8e@suse.cz> Date: Wed, 10 May 2017 08:51:20 +0200 MIME-Version: 1.0 In-Reply-To: <5911C9F9.3020802@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: zhong jiang Cc: akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, hannes@cmpxchg.org, mgorman@techsingularity.net, linux-mm@kvack.org On 05/09/2017 03:54 PM, zhong jiang wrote: > Hi, Vlastimil > > I review the code again. it works well for NUMA. because > khugepaged_prealloc_page will put_page when *hpage is true. > > the memory leak will still exist in !NUMA. because it ingore > the put_page. is it right? I miss something. No, on !NUMA the preallocated and unused new_page is freed by put_page() at the very end of khugepaged_do_scan(). > Thanks > zhongjiang > > On 2017/5/9 20:41, Vlastimil Babka wrote: >> On 05/09/2017 02:20 PM, zhong jiang wrote: >>> On 2017/5/9 19:34, Vlastimil Babka wrote: >>>> On 05/09/2017 12:55 PM, zhongjiang wrote: >>>>> From: zhong jiang >>>>> >>>>> Current, when we prepare a huge page to collapse, due to some >>>>> reasons, it can fail to collapse. At the moment, we should >>>>> release the preallocate huge page. >>>>> >>>>> Signed-off-by: zhong jiang >>>> Hmm, scratch that, there's no memory leak. The pointer to new_page is >>>> stored in *hpage, and put_page() is called all the way up in >>>> khugepaged_do_scan(). >>> I see. I miss it. but why the new_page need to be release all the way. >> AFAIK to support preallocation and reusal of preallocated page for >> collapse attempt in different pmd. It only works for !NUMA so it's >> likely not worth all the trouble and complicated code, so I wouldn't be >> opposed to simplifying this. >> >>> I do not see the count increment when scan success. it save the memory, >>> only when page fault happen. >> I don't understand what you mean here? >> >>> Thanks >>> zhongjiang >>>>> --- >>>>> mm/khugepaged.c | 4 ++++ >>>>> 1 file changed, 4 insertions(+) >>>>> >>>>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >>>>> index 7cb9c88..586b1f1 100644 >>>>> --- a/mm/khugepaged.c >>>>> +++ b/mm/khugepaged.c >>>>> @@ -1082,6 +1082,8 @@ static void collapse_huge_page(struct mm_struct *mm, >>>>> up_write(&mm->mmap_sem); >>>>> out_nolock: >>>>> trace_mm_collapse_huge_page(mm, isolated, result); >>>>> + if (page != NULL && result != SCAN_SUCCEED) >>>>> + put_page(new_page); >>>>> return; >>>>> out: >>>>> mem_cgroup_cancel_charge(new_page, memcg, true); >>>>> @@ -1555,6 +1557,8 @@ static void collapse_shmem(struct mm_struct *mm, >>>>> } >>>>> out: >>>>> VM_BUG_ON(!list_empty(&pagelist)); >>>>> + if (page != NULL && result != SCAN_SUCCEED) >>>>> + put_page(new_page); >>>>> /* TODO: tracepoints */ >>>>> } >>>>> >>>>> >>>> . >>>> >>> >> >> . >> > > -- 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