Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751834AbdHCGi2 (ORCPT ); Thu, 3 Aug 2017 02:38:28 -0400 Received: from mail-pg0-f67.google.com ([74.125.83.67]:34041 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751758AbdHCGi1 (ORCPT ); Thu, 3 Aug 2017 02:38:27 -0400 From: Wei Yang To: akpm@linux-foundation.org, mhocko@suse.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wei Yang Subject: [PATCH] mm/vmalloc: reduce half comparison during pcpu_get_vm_areas() Date: Thu, 3 Aug 2017 14:38:22 +0800 Message-Id: <20170803063822.48702-1-richard.weiyang@gmail.com> X-Mailer: git-send-email 2.11.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1780 Lines: 47 In pcpu_get_vm_areas(), it checks each range is not overlapped. To make sure it is, only (N^2)/2 comparison is necessary, while current code does N^2 times. By starting from the next range, it achieves the goal and the continue could be removed. At the mean time, other two work in this patch: * the overlap check of two ranges could be done with one clause * one typo in comment is fixed. Signed-off-by: Wei Yang --- mm/vmalloc.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 8087451cb332..f33c8350fd83 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2457,7 +2457,7 @@ static unsigned long pvm_determine_end(struct vmap_area **pnext, * matching slot. While scanning, if any of the areas overlaps with * existing vmap_area, the base address is pulled down to fit the * area. Scanning is repeated till all the areas fit and then all - * necessary data structres are inserted and the result is returned. + * necessary data structures are inserted and the result is returned. */ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets, const size_t *sizes, int nr_vms, @@ -2485,15 +2485,11 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets, if (start > offsets[last_area]) last_area = area; - for (area2 = 0; area2 < nr_vms; area2++) { + for (area2 = area + 1; area2 < nr_vms; area2++) { unsigned long start2 = offsets[area2]; unsigned long end2 = start2 + sizes[area2]; - if (area2 == area) - continue; - - BUG_ON(start2 >= start && start2 < end); - BUG_ON(end2 <= end && end2 > start); + BUG_ON(start2 < end && start < end2); } } last_end = offsets[last_area] + sizes[last_area]; -- 2.11.0