From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f50.google.com (mail-wm0-f50.google.com [74.125.82.50]) by kanga.kvack.org (Postfix) with ESMTP id 3516C6B0009 for ; Tue, 19 Jan 2016 13:32:52 -0500 (EST) Received: by mail-wm0-f50.google.com with SMTP id r129so102003963wmr.0 for ; Tue, 19 Jan 2016 10:32:52 -0800 (PST) Received: from mail-wm0-f65.google.com (mail-wm0-f65.google.com. [74.125.82.65]) by mx.google.com with ESMTPS id d132si34913168wmf.70.2016.01.19.10.32.50 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 19 Jan 2016 10:32:50 -0800 (PST) Received: by mail-wm0-f65.google.com with SMTP id u188so25091120wmu.0 for ; Tue, 19 Jan 2016 10:32:50 -0800 (PST) Date: Tue, 19 Jan 2016 19:32:49 +0100 From: Michal Hocko Subject: Re: Mlocked pages statistics shows bogus value. Message-ID: <20160119183249.GA2011@dhcp22.suse.cz> References: <201601191936.HAI26031.HOtJQLOMFFFVOS@I-love.SAKURA.ne.jp> <20160119122101.GA20260@node.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160119122101.GA20260@node.shutemov.name> Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Tetsuo Handa , Michel Lespinasse , Andrew Morton , linux-mm@kvack.org On Tue 19-01-16 14:21:01, Kirill A. Shutemov wrote: [...] > >From 6f80a79dc5f65f29899e396942d40f727cd36480 Mon Sep 17 00:00:00 2001 > From: "Kirill A. Shutemov" > Date: Tue, 19 Jan 2016 14:59:19 +0300 > Subject: [PATCH] mm: fix mlock accouting > > Tetsuo Handa reported underflow of NR_MLOCK on munlock. > > Testcase: > #include > #include > #include > > #define BASE ((void *)0x400000000000) > #define SIZE (1UL << 21) > > int main(int argc, char *argv[]) > { > void *addr; > > system("grep Mlocked /proc/meminfo"); > addr = mmap(BASE, SIZE, PROT_READ | PROT_WRITE, > MAP_ANONYMOUS | MAP_PRIVATE | MAP_LOCKED | MAP_FIXED, > -1, 0); > if (addr == MAP_FAILED) > printf("mmap() failed\n"), exit(1); > munmap(addr, SIZE); > system("grep Mlocked /proc/meminfo"); > return 0; > } > > It happens on munlock_vma_page() due to unfortunate choice of nr_pages > data type: > > __mod_zone_page_state(zone, NR_MLOCK, -nr_pages); > > For unsigned int nr_pages, implicitly casted to long in > __mod_zone_page_state(), it becomes something around UINT_MAX. > > munlock_vma_page() usually called for THP as small pages go though > pagevec. > > Let's make nr_pages singed int. > > Signed-off-by: Kirill A. Shutemov > Fixes: ff6a6da60b89 ("mm: accelerate munlock() treatment of THP pages") > Reported-by: Tetsuo Handa > Cc: Michel Lespinasse $ grep Mlocked /proc/meminfo Mlocked: 10840497455108 kB I've started seeing the same issue recently but was too busy to track it down. Thanks! Mentioning 6cdb18ad98a4 ("mm/vmstat: fix overflow in mod_zone_page_state()") would be really helpful here. Acked-by: Michal Hocko > --- > mm/mlock.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/mlock.c b/mm/mlock.c > index e1e2b1207bf2..96f001041928 100644 > --- a/mm/mlock.c > +++ b/mm/mlock.c > @@ -175,7 +175,7 @@ static void __munlock_isolation_failed(struct page *page) > */ > unsigned int munlock_vma_page(struct page *page) > { > - unsigned int nr_pages; > + int nr_pages; > struct zone *zone = page_zone(page); > > /* For try_to_munlock() and to serialize with page migration */ > -- > Kirill A. Shutemov > > -- > 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 -- 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