From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753718AbdGJLM0 (ORCPT ); Mon, 10 Jul 2017 07:12:26 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:36491 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753662AbdGJLMY (ORCPT ); Mon, 10 Jul 2017 07:12:24 -0400 From: Anshuman Khandual To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, mike.kravetz@oracle.com Subject: [RFC] mm/mremap: Remove redundant checks inside vma_expandable() Date: Mon, 10 Jul 2017 16:40:59 +0530 X-Mailer: git-send-email 2.9.3 X-TM-AS-MML: disable x-cbid: 17071011-0008-0000-0000-0000014EF8E3 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17071011-0009-0000-0000-0000097F56F0 Message-Id: <20170710111059.30795-1-khandual@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-07-10_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=3 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1707100200 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org As 'delta' is an unsigned long, 'end' (vma->vm_end + delta) cannot be less than 'vma->vm_end'. Checking for availability of virtual address range at the end of the VMA for the incremental size is also reduntant at this point. Hence drop them both. Signed-off-by: Anshuman Khandual --- The following test program achieves fatser execution time with this change. #include #include #include #include #include #include #define ALLOC_SIZE 0x10000UL #define MAX_COUNT 1024 * 1024 int main(int argc, char *argv[]) { unsigned long count; char *ptr; ptr = mmap(NULL, ALLOC_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE| MAP_ANONYMOUS, -1, 0); if (ptr == MAP_FAILED) { perror("map() failed"); return -1; } memset(ptr, 0, ALLOC_SIZE); for (count = 1; count <= MAX_COUNT; count++) { ptr = (char *) mremap(ptr, ALLOC_SIZE * count, ALLOC_SIZE * (count + 1), 1); if (ptr == MAP_FAILED) { perror("mremap() failed"); printf("At %lu size", ALLOC_SIZE * (count + 1)); return -1; } /* memset(ptr, 0, ALLOC_SIZE * (count + 1)); */ } for (count = MAX_COUNT; count > 1; count--) { ptr = (char *) mremap(ptr, ALLOC_SIZE * count, ALLOC_SIZE * (count - 1), 1); if (ptr == MAP_FAILED) { perror("mremap() failed"); printf("At %lu size", ALLOC_SIZE * (count - 1)); return -1; } /* memset(ptr, 0, ALLOC_SIZE * (count - 1)); */ } return 0; } mm/mremap.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/mm/mremap.c b/mm/mremap.c index cd8a1b1..b937c28 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -487,12 +487,9 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len, static int vma_expandable(struct vm_area_struct *vma, unsigned long delta) { unsigned long end = vma->vm_end + delta; - if (end < vma->vm_end) /* overflow */ - return 0; - if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */ - return 0; - if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start, - 0, MAP_FIXED) & ~PAGE_MASK) + + /* Intersection with next VMA */ + if (vma->vm_next && vma->vm_next->vm_start < end) return 0; return 1; } -- 1.8.5.2