Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754675Ab0DWB06 (ORCPT ); Thu, 22 Apr 2010 21:26:58 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:53990 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753875Ab0DWB04 (ORCPT ); Thu, 22 Apr 2010 21:26:56 -0400 Message-ID: <4BD0F797.6020704@cn.fujitsu.com> Date: Fri, 23 Apr 2010 09:27:51 +0800 From: Miao Xie Reply-To: miaox@cn.fujitsu.com User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.1.9) Gecko/20100317 Thunderbird/3.0.4 MIME-Version: 1.0 To: David Rientjes CC: Lee Schermerhorn , Nick Piggin , Paul Menage , Andrew Morton , Linux-Kernel , Linux-MM Subject: Re: [PATCH 1/2] mm: fix bugs of mpol_rebind_nodemask() References: <4BD05929.8040900@cn.fujitsu.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2174 Lines: 66 on 2010-4-23 5:20, David Rientjes wrote: > On Thu, 22 Apr 2010, Miao Xie wrote: > >> - local variable might be an empty nodemask, so must be checked before setting >> pol->v.nodes to it. >> >> - nodes_remap() may cause the weight of pol->v.nodes being monotonic decreasing. >> and never become large even we pass a nodemask with large weight after >> ->v.nodes become little. >> > > That's always been the intention of rebinding a mempolicy nodemask: we > remap the current mempolicy nodes over the new nodemask given the set of > allowed nodes. The nodes_remap() shouldn't be removed. Suppose the current mempolicy nodes is 0-2, we can remap it from 0-2 to 2, then we can remap it from 2 to 1, but we can't remap it from 2 to 0-2. that is to say it can't be remaped to a large set of allowed nodes, and the task just can use the small set of nodes for ever, even the large set of nodes is allowed, I think it is unreasonable. Thanks Miao > >> this patch fixes these two problem. >> >> Signed-off-by: Miao Xie >> --- >> mm/mempolicy.c | 9 ++++++--- >> 1 files changed, 6 insertions(+), 3 deletions(-) >> >> diff --git a/mm/mempolicy.c b/mm/mempolicy.c >> index 08f40a2..03ba9fc 100644 >> --- a/mm/mempolicy.c >> +++ b/mm/mempolicy.c >> @@ -291,12 +291,15 @@ static void mpol_rebind_nodemask(struct mempolicy *pol, >> else if (pol->flags & MPOL_F_RELATIVE_NODES) >> mpol_relative_nodemask(&tmp, &pol->w.user_nodemask, nodes); >> else { >> - nodes_remap(tmp, pol->v.nodes, pol->w.cpuset_mems_allowed, >> - *nodes); >> + tmp = *nodes; >> pol->w.cpuset_mems_allowed = *nodes; >> } >> >> - pol->v.nodes = tmp; >> + if (nodes_empty(tmp)) >> + pol->v.nodes = *nodes; >> + else >> + pol->v.nodes = tmp; >> + >> if (!node_isset(current->il_next, tmp)) { >> current->il_next = next_node(current->il_next, tmp); >> if (current->il_next >= MAX_NUMNODES) > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/