From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx155.postini.com [74.125.245.155]) by kanga.kvack.org (Postfix) with SMTP id A56986B004A for ; Mon, 27 Feb 2012 22:03:17 -0500 (EST) Date: Mon, 27 Feb 2012 19:04:32 -0800 From: Andrew Morton Subject: Re: [PATCH] HUGETLBFS: Align memory request to multiple of huge page size to avoid underallocating. Message-Id: <20120227190432.55d7399a.akpm@linux-foundation.org> In-Reply-To: <4F4C4215.5020108@utoronto.ca> References: <1330351768-14874-1-git-send-email-steven.truelove@utoronto.ca> <20120227154217.0a0d5a06.akpm@linux-foundation.org> <4F4C4215.5020108@utoronto.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Steven Truelove Cc: wli@holomorphy.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org On Mon, 27 Feb 2012 21:55:17 -0500 Steven Truelove wrote: > > A few things... > > > > - sys_mmap_pgoff() does the rounding up prior to calling > > hugetlb_file_setup(). ipc/shm.c:newseg() does not. > > > > We should be consistent here: do it in the caller or the callee, > > not both (or neither!). I guess doing it in the callee would be > > best. > > > > - The above code could/should have used ALIGN(). Or round_up(): the > > difference presently escapes me, even though it was so obvious that > > we left all these things undocumented. > > > > - What's the point in aligning the length if we don't also look at > > the start address? If that isn't a multiple of huge_page_size(), we > > will need an additional page. > > > > Since mmap has an address to check and shmget does not, if the address > is going to be checked it will need to be in the caller. Or pass a value of 0 from shmget. > If you like, I > will leave the size check in hugetlb_file_setup() and remove the size > check from mmap_pgoff, but replace it with a check of the address. That > will centralize the common check (size of buffer), and let mmap_pgoff > check the part that is unique to it. Patch shortly. > > Steven Truelove -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org