From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx150.postini.com [74.125.245.150]) by kanga.kvack.org (Postfix) with SMTP id 0E6366B0006 for ; Tue, 5 Mar 2013 03:50:32 -0500 (EST) From: Arnd Bergmann Subject: Re: [RFC/PATCH 0/5] Contiguous Memory Allocator and get_user_pages() Date: Tue, 5 Mar 2013 08:50:26 +0000 References: <1362466679-17111-1-git-send-email-m.szyprowski@samsung.com> In-Reply-To: <1362466679-17111-1-git-send-email-m.szyprowski@samsung.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Message-Id: <201303050850.26615.arnd@arndb.de> Sender: owner-linux-mm@kvack.org List-ID: To: Marek Szyprowski Cc: linux-mm@kvack.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, Kyungmin Park , Andrew Morton , Mel Gorman , Michal Nazarewicz , Minchan Kim , Bartlomiej Zolnierkiewicz On Tuesday 05 March 2013, Marek Szyprowski wrote: > To solving this issue requires preventing locking of the pages, which > are placed in CMA regions, for a long time. Our idea is to migrate > anonymous page content before locking the page in get_user_pages(). This > cannot be done automatically, as get_user_pages() interface is used very > often for various operations, which usually last for a short period of > time (like for example exec syscall). We have added a new flag > indicating that the given get_user_space() call will grab pages for a > long time, thus it is suitable to use the migration workaround in such > cases. Can you explain the tradeoff here? I would have expected that the default should be to migrate pages out, and annotate the instances that we know are performance critical and short-lived. That would at least appear more reliable to me. Arnd -- 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