Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753431Ab1C1CDn (ORCPT ); Sun, 27 Mar 2011 22:03:43 -0400 Received: from mga14.intel.com ([143.182.124.37]:22968 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753282Ab1C1CDn (ORCPT ); Sun, 27 Mar 2011 22:03:43 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.63,252,1299484800"; d="scan'208";a="409474650" Subject: [PATCH]mmap: not merge cloned VMA From: Shaohua Li To: Andrew Morton Cc: linux-mm , lkml , Rik van Riel , Hugh Dickins Content-Type: text/plain; charset="UTF-8" Date: Mon, 28 Mar 2011 09:58:54 +0800 Message-ID: <1301277534.3981.26.camel@sli10-conroe> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2499 Lines: 66 Avoid merging a VMA with another VMA which is cloned from parent process. The cloned VMA shares lock with parent process's VMA. If we do the merge, more vma area (even the new range is only for current process) uses perent process's anon_vma lock, so introduces scalability issues. find_mergeable_anon_vma already considers this. Signed-off-by: Shaohua Li --- mm/mmap.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) Index: linux/mm/mmap.c =================================================================== --- linux.orig/mm/mmap.c 2011-03-24 09:37:28.000000000 +0800 +++ linux/mm/mmap.c 2011-03-24 09:48:37.000000000 +0800 @@ -699,9 +699,13 @@ static inline int is_mergeable_vma(struc } static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1, - struct anon_vma *anon_vma2) + struct anon_vma *anon_vma2, + struct vm_area_struct *vma) { - return !anon_vma1 || !anon_vma2 || (anon_vma1 == anon_vma2); + if ((!anon_vma1 || !anon_vma2) && (!vma || + list_is_singular(&vma->anon_vma_chain))) + return 1; + return anon_vma1 == anon_vma2; } /* @@ -720,7 +724,7 @@ can_vma_merge_before(struct vm_area_stru struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff) { if (is_mergeable_vma(vma, file, vm_flags) && - is_mergeable_anon_vma(anon_vma, vma->anon_vma)) { + is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) { if (vma->vm_pgoff == vm_pgoff) return 1; } @@ -739,7 +743,7 @@ can_vma_merge_after(struct vm_area_struc struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff) { if (is_mergeable_vma(vma, file, vm_flags) && - is_mergeable_anon_vma(anon_vma, vma->anon_vma)) { + is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) { pgoff_t vm_pglen; vm_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT; if (vma->vm_pgoff + vm_pglen == vm_pgoff) @@ -817,7 +821,7 @@ struct vm_area_struct *vma_merge(struct can_vma_merge_before(next, vm_flags, anon_vma, file, pgoff+pglen) && is_mergeable_anon_vma(prev->anon_vma, - next->anon_vma)) { + next->anon_vma, NULL)) { /* cases 1, 6 */ err = vma_adjust(prev, prev->vm_start, next->vm_end, prev->vm_pgoff, NULL); -- 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/