From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sat, 21 Aug 2004 14:01:21 +0900 (JST) Message-Id: <20040821.140121.41645060.taka@valinux.co.jp> Subject: Re: [Lhms-devel] Re: [RFC] free_area[] bitmap elimination [0/3] From: Hirokazu Takahashi In-Reply-To: <4126D6E5.9070804@jp.fujitsu.com> References: <4126B3F9.90706@jp.fujitsu.com> <20040821025543.GS11200@holomorphy.com> <4126D6E5.9070804@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: kamezawa.hiroyu@jp.fujitsu.com Cc: wli@holomorphy.com, linux-mm@kvack.org, lhms-devel@lists.sourceforge.net List-ID: Hi, > William Lee Irwin III wrote: > > > On Sat, Aug 21, 2004 at 11:31:21AM +0900, Hiroyuki KAMEZAWA wrote: > > > >>This patch removes bitmap from buddy allocator used in > >>alloc_pages()/free_pages() in the kernel 2.6.8.1. > > > > > Complexity maybe. But one serious issue this addresses beyond the needs > > of hotplug memory is that the buddy bitmaps are a heavily random-access > > data structures not used elsewhere. Consolidating them into the page > > structures should improve cache locality and motivate this patch beyond > > just the needs of hotplug memory. Furthermore, the patch also reduces > > the kernel's overall memory footprint by a small amount. > > > > However, I'm concerned about the effectiveness of this specific > > algorithm for coalescing. A more detailed description may help explain > > why the effectiveness of coalescing is preserved. > > > > Thanks for your comment, William-san. > I'd like to add detailed description on my patch. > I'm now afraid of the case of memory-hole, I should add page_ivs_valid(buddy1) before > accessing buddy1. What do you think about my idea I just posted. > In my understanding, the patch assumes that size of mem_map[] in each > zone must be multiple of 2^MAX_ORDER, right? > But it doesn't seem it's a big problem, as we can just allocate extra > mem_map[] to round up if it isn't. I think this may help the buddy allocator to work withtout adding page_ivs_valid(buddy1). Thank you, Hirokazu Takahashi. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org