From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753722Ab3EULHO (ORCPT ); Tue, 21 May 2013 07:07:14 -0400 Received: from hydra.sisk.pl ([212.160.235.94]:42731 "EHLO hydra.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750816Ab3EULHM (ORCPT ); Tue, 21 May 2013 07:07:12 -0400 From: "Rafael J. Wysocki" 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 Subject: Re: [PATCH 2/2 v2, RFC] Driver core: Introduce offline/online callbacks for memory blocks Date: Tue, 21 May 2013 13:15:54 +0200 Message-ID: <1824290.fKsAJTo9gA@vostro.rjw.lan> User-Agent: KMail/4.9.5 (Linux/3.9.0+; KDE/4.9.5; x86_64; ; ) In-Reply-To: <519B1641.1020906@cn.fujitsu.com> References: <1576321.HU0tZ4cGWk@vostro.rjw.lan> <19540491.PRsM4lKIYM@vostro.rjw.lan> <519B1641.1020906@cn.fujitsu.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday, May 21, 2013 02:37:53 PM Tang Chen wrote: > Hi Rafael, > > Please see below. > > On 05/04/2013 07:21 PM, Rafael J. Wysocki wrote: > ...... > > static BLOCKING_NOTIFIER_HEAD(memory_chain); > > @@ -278,33 +283,64 @@ static int __memory_block_change_state(s > > { > > int ret = 0; > > > > - if (mem->state != from_state_req) { > > - ret = -EINVAL; > > - goto out; > > - } > > + if (mem->state != from_state_req) > > + return -EINVAL; > > > > if (to_state == MEM_OFFLINE) > > mem->state = MEM_GOING_OFFLINE; > > > > ret = memory_block_action(mem->start_section_nr, to_state, online_type); > > - > > if (ret) { > > mem->state = from_state_req; > > - goto out; > > + } else { > > + 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? > ...... > } > > 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? > Reviewed-by: Tang Chen > > Thanks. :) Thanks for your comments, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.