Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759225Ab3DAWYC (ORCPT ); Mon, 1 Apr 2013 18:24:02 -0400 Received: from mail-da0-f53.google.com ([209.85.210.53]:65025 "EHLO mail-da0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758530Ab3DAWXg (ORCPT ); Mon, 1 Apr 2013 18:23:36 -0400 Date: Mon, 1 Apr 2013 15:23:33 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Zhouping Liu cc: Andrea Arcangeli , Hugh Dickins , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Amos Kong Subject: Re: THP: AnonHugePages in /proc/[pid]/smaps is correct or not? In-Reply-To: <383590596.664138.1364803227470.JavaMail.root@redhat.com> Message-ID: References: <383590596.664138.1364803227470.JavaMail.root@redhat.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2256 Lines: 78 On Mon, 1 Apr 2013, Zhouping Liu wrote: > Hi all, > > I found THP can't correctly distinguish one anonymous hugepage map. > > 1. when /sys/kernel/mm/transparent_hugepage/enabled is 'always', the > amount of THP always is one less. > It's not a problem with identifying an anonymous mapping as a hugepage, setting thp enabled to "always" does not guarantee that they will always be allocatable or that your mmap() will be 2MB aligned. Your sample code is using mmap() instead of posix_memalign() so you'll probably only get 100% hugepages only 1/512th of the time. > 2. when /sys/kernel/mm/transparent_hugepage/enabled is 'madvise', THP can't > distinguish any one anonymous hugepage size: > > Testing code: > -------- snip -------- > unsigned long hugepagesize = (1UL << 21); > > int main() > { > void *addr; > int i; > > printf("pid is %d\n", getpid()); > > for (i = 0; i < 5; i++) { > addr = mmap(NULL, hugepagesize, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0); > > if (addr == MAP_FAILED) { > perror("mmap"); > return -1; > } > > if (madvise(addr, hugepagesize, MADV_HUGEPAGE) == -1) { > perror("madvise"); > return -1; > } > > memset(addr, i, hugepagesize); > } > > sleep(50); > > return 0; > } > --------- snip ---------- > > The result is that it can't find any AnonHugePages from /proc/[pid]/smaps : > -------------- snip ------- > 7f0b38cd0000-7f0b396d0000 rw-p 00000000 00:00 0 > Size: 10240 kB > Rss: 10240 kB > Pss: 10240 kB > Shared_Clean: 0 kB > Shared_Dirty: 0 kB > Private_Clean: 0 kB > Private_Dirty: 10240 kB > Referenced: 10240 kB > Anonymous: 10240 kB > AnonHugePages: 0 kB > Swap: 0 kB > KernelPageSize: 4 kB > MMUPageSize: 4 kB > Locked: 0 kB > VmFlags: rd wr mr mw me ac "hg" would be shown in VmFlags if your MADV_HUGEPAGE was successful, are you sure this is the right vma? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/