Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764536AbXESSW6 (ORCPT ); Sat, 19 May 2007 14:22:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758195AbXESSWw (ORCPT ); Sat, 19 May 2007 14:22:52 -0400 Received: from holomorphy.com ([66.93.40.71]:39000 "EHLO holomorphy.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759485AbXESSWv (ORCPT ); Sat, 19 May 2007 14:22:51 -0400 Date: Sat, 19 May 2007 11:21:23 -0700 From: William Lee Irwin III To: Eric Dumazet Cc: Andrew Morton , "linux-mm@kvack.org" , linux kernel , David Miller Subject: Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize Message-ID: <20070519182123.GD19966@holomorphy.com> References: <20070518115454.d3e32f4d.dada1@cosmosbay.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070518115454.d3e32f4d.dada1@cosmosbay.com> Organization: The Domain of Holomorphy User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1065 Lines: 23 On Fri, May 18, 2007 at 11:54:54AM +0200, Eric Dumazet wrote: > alloc_large_system_hash() is called at boot time to allocate space > for several large hash tables. > Lately, TCP hash table was changed and its bucketsize is not a > power-of-two anymore. > On most setups, alloc_large_system_hash() allocates one big page > (order > 0) with __get_free_pages(GFP_ATOMIC, order). This single > high_order page has a power-of-two size, bigger than the needed size. > We can free all pages that wont be used by the hash table. > On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory. > TCP established hash table entries: 32768 (order: 6, 393216 bytes) The proper way to do this is to convert the large system hashtable users to use some data structure / algorithm other than hashing by separate chaining. -- wli - 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/