From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752121AbeDELfK (ORCPT ); Thu, 5 Apr 2018 07:35:10 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:60844 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751470AbeDELfG (ORCPT ); Thu, 5 Apr 2018 07:35:06 -0400 Date: Thu, 5 Apr 2018 04:34:44 -0700 From: Matthew Wilcox To: Jia He Cc: Russell King , Catalin Marinas , Will Deacon , Mark Rutland , Ard Biesheuvel , Andrew Morton , Michal Hocko , Wei Yang , Kees Cook , Laura Abbott , Vladimir Murzin , Philip Derrin , AKASHI Takahiro , James Morse , Steve Capper , Pavel Tatashin , Gioh Kim , Vlastimil Babka , Mel Gorman , Johannes Weiner , Kemi Wang , Petr Tesarik , YASUAKI ISHIMATSU , Andrey Ryabinin , Nikolay Borisov , Daniel Jordan , Daniel Vacek , Eugeniu Rosca , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Jia He Subject: Re: [PATCH v7 2/5] arm: arm64: page_alloc: reduce unnecessary binary search in memblock_next_valid_pfn() Message-ID: <20180405113444.GB2647@bombadil.infradead.org> References: <1522915478-5044-1-git-send-email-hejianet@gmail.com> <1522915478-5044-3-git-send-email-hejianet@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1522915478-5044-3-git-send-email-hejianet@gmail.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 05, 2018 at 01:04:35AM -0700, Jia He wrote: > Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns > where possible") optimized the loop in memmap_init_zone(). But there is > still some room for improvement. E.g. if pfn and pfn+1 are in the same > memblock region, we can simply pfn++ instead of doing the binary search > in memblock_next_valid_pfn. Sure, but I bet if we are >end_pfn, we're almost certainly going to the start_pfn of the next block, so why not test that as well? > + /* fast path, return pfn+1 if next pfn is in the same region */ > + if (early_region_idx != -1) { > + start_pfn = PFN_DOWN(regions[early_region_idx].base); > + end_pfn = PFN_DOWN(regions[early_region_idx].base + > + regions[early_region_idx].size); > + > + if (pfn >= start_pfn && pfn < end_pfn) > + return pfn; early_region_idx++; start_pfn = PFN_DOWN(regions[early_region_idx].base); if (pfn >= end_pfn && pfn <= start_pfn) return start_pfn; > + } From mboxrd@z Thu Jan 1 00:00:00 1970 From: willy@infradead.org (Matthew Wilcox) Date: Thu, 5 Apr 2018 04:34:44 -0700 Subject: [PATCH v7 2/5] arm: arm64: page_alloc: reduce unnecessary binary search in memblock_next_valid_pfn() In-Reply-To: <1522915478-5044-3-git-send-email-hejianet@gmail.com> References: <1522915478-5044-1-git-send-email-hejianet@gmail.com> <1522915478-5044-3-git-send-email-hejianet@gmail.com> Message-ID: <20180405113444.GB2647@bombadil.infradead.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Apr 05, 2018 at 01:04:35AM -0700, Jia He wrote: > Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns > where possible") optimized the loop in memmap_init_zone(). But there is > still some room for improvement. E.g. if pfn and pfn+1 are in the same > memblock region, we can simply pfn++ instead of doing the binary search > in memblock_next_valid_pfn. Sure, but I bet if we are >end_pfn, we're almost certainly going to the start_pfn of the next block, so why not test that as well? > + /* fast path, return pfn+1 if next pfn is in the same region */ > + if (early_region_idx != -1) { > + start_pfn = PFN_DOWN(regions[early_region_idx].base); > + end_pfn = PFN_DOWN(regions[early_region_idx].base + > + regions[early_region_idx].size); > + > + if (pfn >= start_pfn && pfn < end_pfn) > + return pfn; early_region_idx++; start_pfn = PFN_DOWN(regions[early_region_idx].base); if (pfn >= end_pfn && pfn <= start_pfn) return start_pfn; > + }