From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx172.postini.com [74.125.245.172]) by kanga.kvack.org (Postfix) with SMTP id 5D1206B0093 for ; Wed, 22 May 2013 06:34:07 -0400 (EDT) From: "Rafael J. Wysocki" Subject: Re: [PATCH 2/2 v2, RFC] Driver core: Introduce offline/online callbacks for memory blocks Date: Wed, 22 May 2013 12:42:50 +0200 Message-ID: <2525744.qpOuRMa9WS@vostro.rjw.lan> In-Reply-To: <519C4D6E.6080902@cn.fujitsu.com> References: <1576321.HU0tZ4cGWk@vostro.rjw.lan> <1824290.fKsAJTo9gA@vostro.rjw.lan> <519C4D6E.6080902@cn.fujitsu.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: owner-linux-mm@kvack.org List-ID: To: Tang Chen Cc: Greg Kroah-Hartman , Toshi Kani , ACPI Devel Maling List , LKML , isimatu.yasuaki@jp.fujitsu.com, vasilis.liaskovitis@profitbricks.com, Len Brown , linux-mm@kvack.org On Wednesday, May 22, 2013 12:45:34 PM Tang Chen wrote: > Hi Rafael, > > On 05/21/2013 07:15 PM, Rafael J. Wysocki wrote: > ...... > >>> + mem->state = to_state; > >>> + if (to_state == MEM_ONLINE) > >>> + mem->last_online = online_type; > >> > >> Why do we need to remember last online type ? > >> > >> And as far as I know, we can obtain which zone a page was in last time it > >> was onlined by check page->flags, just like online_pages() does. If we > >> use online_kernel or online_movable, the zone boundary will be > >> recalculated. > >> So we don't need to remember the last online type. > >> > >> Seeing from your patch, I guess memory_subsys_online() can only handle > >> online and offline. So mem->last_online is used to remember what user has > >> done through the original way to trigger memory hot-remove, right ? And > >> when > >> user does it in this new way, it just does the same thing as user does last > >> time. > >> > >> But I still think we don't need to remember it because if finally you call > >> online_pages(), it just does the same thing as last time by default. > >> > >> online_pages() > >> { > >> ...... > >> if (online_type == ONLINE_KERNEL ...... > >> > >> if (online_type == ONLINE_MOVABLE...... > >> > >> zone = page_zone(pfn_to_page(pfn)); > >> > >> /* Here, the page will be put into the zone which it belong to last > >> time. */ > > > > To be honest, it wasn't entirely clear to me that online_pages() would do the > > same thing as last time by default. Suppose, for example, that the previous > > online_type was ONLINE_MOVABLE. How online_pages() is supposed to know that > > it should do the move_pfn_zone_right() if we don't tell it to do that? Or > > is that unnecessary, because it's already been done previously? > > Yes, it is unnecessary. move_pfn_zone_right/left() will modify the zone > related > bits in page->flags. But when the page is offline, the zone related bits in > page->flags will not change. So when it is online again, by dafault, it > will > be in the zone which it was in last time. > > ...... > > >> > >> I just thought of it. Maybe I missed something in your design. Please tell > >> me if I'm wrong. > > > > Well, so what should be passed to __memory_block_change_state() in > > memory_subsys_online()? -1? > > If you want to keep the last time status, you can pass ONLINE_KEEP. > Or -1 is all right. > > Thanks. :) OK, thanks for the info. Since the $subject patch is on my acpi-hotplug branch which has gone public already (and cannot be rebased), I'll prepare a patch with the change you're recommending on top of it. Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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