From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f70.google.com (mail-oi0-f70.google.com [209.85.218.70]) by kanga.kvack.org (Postfix) with ESMTP id 1B7BD280842 for ; Wed, 10 May 2017 04:10:17 -0400 (EDT) Received: by mail-oi0-f70.google.com with SMTP id t9so25397779oih.13 for ; Wed, 10 May 2017 01:10:17 -0700 (PDT) Received: from szxga03-in.huawei.com (szxga03-in.huawei.com. [45.249.212.189]) by mx.google.com with ESMTPS id 81si973937otj.203.2017.05.10.01.10.14 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 10 May 2017 01:10:16 -0700 (PDT) Message-ID: <5912C845.1080008@huawei.com> Date: Wed, 10 May 2017 15:59:01 +0800 From: zhong jiang MIME-Version: 1.0 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> <6810ea54-faed-fcc1-7751-ff91fa3f9d8e@suse.cz> In-Reply-To: <6810ea54-faed-fcc1-7751-ff91fa3f9d8e@suse.cz> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, hannes@cmpxchg.org, mgorman@techsingularity.net, linux-mm@kvack.org On 2017/5/10 14:51, Vlastimil Babka wrote: > 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(). Thank you for clarification. I should consider more before sending the patch. Thanks zhongjiang >> 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