From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753131Ab3EVEmo (ORCPT ); Wed, 22 May 2013 00:42:44 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:5003 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750853Ab3EVEmn (ORCPT ); Wed, 22 May 2013 00:42:43 -0400 X-IronPort-AV: E=Sophos;i="4.87,719,1363104000"; d="scan'208";a="7330463" Message-ID: <519C4D6E.6080902@cn.fujitsu.com> Date: Wed, 22 May 2013 12:45:34 +0800 From: Tang Chen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: "Rafael J. Wysocki" 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 Subject: Re: [PATCH 2/2 v2, RFC] Driver core: Introduce offline/online callbacks for memory blocks References: <1576321.HU0tZ4cGWk@vostro.rjw.lan> <19540491.PRsM4lKIYM@vostro.rjw.lan> <519B1641.1020906@cn.fujitsu.com> <1824290.fKsAJTo9gA@vostro.rjw.lan> In-Reply-To: <1824290.fKsAJTo9gA@vostro.rjw.lan> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/05/22 12:41:19, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/05/22 12:41:23, Serialize complete at 2013/05/22 12:41:23 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. :) > >> Reviewed-by: Tang Chen >> >> Thanks. :) > > Thanks for your comments, > Rafael > >