From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx175.postini.com [74.125.245.175]) by kanga.kvack.org (Postfix) with SMTP id 5C7D36B0072 for ; Thu, 20 Dec 2012 15:28:16 -0500 (EST) Received: by mail-pa0-f46.google.com with SMTP id bh2so2338909pad.33 for ; Thu, 20 Dec 2012 12:28:15 -0800 (PST) Date: Thu, 20 Dec 2012 12:28:13 -0800 (PST) From: David Rientjes Subject: Re: [PATCH 04/15] mm/huge_memory: use new hashtable implementation In-Reply-To: <50D27707.7060309@oracle.com> Message-ID: References: <1355756497-15834-1-git-send-email-sasha.levin@oracle.com> <1355756497-15834-4-git-send-email-sasha.levin@oracle.com> <50D27707.7060309@oracle.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Sasha Levin Cc: Andrew Morton , "Kirill A. Shutemov" , Xiao Guangrong , Andrea Arcangeli , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Wed, 19 Dec 2012, Sasha Levin wrote: > In this case, the downside is that you'll waste 8KB if hugepages aren't available, > but the upside is that you'll have one less dereference when accessing the > hashtable. > > If the 8KB saving is preferable here I'll drop the patch and come back when > dynamic hashtable is supported. > If a distro releases with CONFIG_TRANSPARNET_HUGEPAGE=y and a user is running on a processor that does not support pse then this just cost them 8KB for no reason. The overhead by simply enabling CONFIG_TRANSPARENT_HUGEPAGE is worse in this scenario, but this is whole reason for having the dynamic allocation in the original code. If there's a compelling reason for why we want this change, then that fact should at least be documented. Could you propose a v2 that includes fixes for the other problems that were mentioned? -- 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