From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with ESMTP id DC34E8D003B for ; Mon, 4 Apr 2011 09:18:20 -0400 (EDT) Received: by ewy9 with SMTP id 9so2184451ewy.14 for ; Mon, 04 Apr 2011 06:15:10 -0700 (PDT) Content-Type: text/plain; charset=utf-8; format=flowed; delsp=yes Subject: Re: [PATCH 04/12] mm: alloc_contig_freed_pages() added References: <1301577368-16095-1-git-send-email-m.szyprowski@samsung.com> <1301577368-16095-5-git-send-email-m.szyprowski@samsung.com> <1301587083.31087.1032.camel@nimitz> <1301606078.31087.1275.camel@nimitz> <1301610411.30870.29.camel@nimitz> <1301666596.30870.176.camel@nimitz> Date: Mon, 04 Apr 2011 15:15:07 +0200 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: "Michal Nazarewicz" Message-ID: In-Reply-To: <1301666596.30870.176.camel@nimitz> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: Marek Szyprowski , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org, linux-mm@kvack.org, Kyungmin Park , Andrew Morton , KAMEZAWA Hiroyuki , Ankita Garg , Daniel Walker , Johan MOSSBERG , Mel Gorman , Pawel Osciak > On Fri, 2011-04-01 at 00:51 +0200, Michal Nazarewicz wrote: >> The function is called from alloc_contig_range() (see patch 05/12) which >> makes sure that the PFN is valid. Situation where there is not enough >> space is caught earlier in alloc_contig_range(). >> >> alloc_contig_freed_pages() must be given a valid PFN range such that all >> the pages in that range are free (as in are within the region tracked by >> page allocator) and of MIGRATE_ISOLATE so that page allocator won't >> touch them. On Fri, 01 Apr 2011 16:03:16 +0200, Dave Hansen wrote: > OK, so it really is a low-level function only. How about a comment that > explicitly says this? "Only called from $FOO with the area already > isolated." It probably also deserves an __ prefix. Yes, it's not really for general use. Comment may indeed be useful here. >> That's why invalid PFN is a bug in the caller and not an exception that >> has to be handled. >> >> Also, the function is not called during boot time. It is called while >> system is already running. > What kind of success have you had running this in practice? I'd be > worried that some silly task or a sticky dentry would end up in the > range that you want to allocate in. I'm not sure what you are asking. The function requires the range to be marked as MIGRATE_ISOLATE and all pages being free, so nothing can be allocated there while the function is running. If you are asking about CMA in general, the range that CMA uses is marked as MIGRATE_CMA (a new migrate type) which means that only MIGRATE_MOVABLE pages can be allocated there. This means, that in theory, if there is enough memory the pages can always be moved out of the region. At leasts that's my understanding of the type. If this is correct, the allocation should always succeed provided enough memory for the pages within the region to be moved to is available. As of practice, I have run some simple test to see if the code works and they succeeded. Also, Marek has run some test with actual hardware and those worked well as well (but I'll let Marek talk about any details). -- Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michal "mina86" Nazarewicz (o o) ooo +----------ooO--(_)--Ooo-- -- 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