From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx136.postini.com [74.125.245.136]) by kanga.kvack.org (Postfix) with SMTP id 7BA2F6B0005 for ; Mon, 18 Mar 2013 15:14:59 -0400 (EDT) Message-ID: <514767A5.4020601@zytor.com> Date: Mon, 18 Mar 2013 12:14:45 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 Subject: Re: [PATCH] x86: mm: accurate the comments for STEP_SIZE_SHIFT macro References: <1363602068-11924-1-git-send-email-linfeng@cn.fujitsu.com> <51476402.7050102@zytor.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Yinghai Lu Cc: Lin Feng , akpm@linux-foundation.org, linux-mm@kvack.org, x86@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, penberg@kernel.org, jacob.shin@amd.com On 03/18/2013 12:13 PM, Yinghai Lu wrote: >> >> No, it doesn't. This is C, not elementary school Now I'm really bothered. >> >> The comment doesn't say *why* (PUD_SHIFT-PMD_SHIFT)/2 or any other >> variant is correct, furthermore I suspect that the +1 is misplaced. >> However, what is really needed is: >> >> 1. Someone needs to explain what the logic should be and why, and >> 2. replace the macro with a symbolic macro, not with a constant and a >> comment explaining, incorrectly, how that value was derived. > > yes, we should find out free_mem_size instead to decide next step size. > > But that will come out page table size estimation problem again. > Sorry, that comment is double nonsense for someone who isn't intimately familiar with the code, and it sounds like it is just plain wrong. Instead, try to explain why 5 is the correct value in the current code and how it is (or should be!) derived. -hpa -- 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