From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sat, 19 May 2007 11:21:23 -0700 From: William Lee Irwin III 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> Sender: owner-linux-mm@kvack.org Return-Path: To: Eric Dumazet Cc: Andrew Morton , "linux-mm@kvack.org" , linux kernel , David Miller List-ID: 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, 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: email@kvack.org