From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 3D8856B01B1 for ; Fri, 21 May 2010 00:06:15 -0400 (EDT) From: "Guo, Chaohong" Date: Fri, 21 May 2010 12:05:16 +0800 Subject: RE: [PATCH] online CPU before memory failed in pcpu_alloc_pages() Message-ID: References: <1274163442-7081-1-git-send-email-chaohong_guo@linux.intel.com> <20100520134359.fdfb397e.akpm@linux-foundation.org> In-Reply-To: <20100520134359.fdfb397e.akpm@linux-foundation.org> Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org To: Andrew Morton , minskey guo Cc: "linux-mm@kvack.org" , "prarit@redhat.com" , "Kleen, Andi" , "linux-kernel@vger.kernel.org" , Tejun Heo , "stable@kernel.org" List-ID: >> The operation of "enable CPU to online before memory within a node" >> fails in some case according to Prarit. The warnings as follows: >> >> Pid: 7440, comm: bash Not tainted 2.6.32 #2 >> Call Trace: >> [] pcpu_alloc+0xa05/0xa70 >> [] __alloc_percpu+0x10/0x20 >> [] __create_workqueue_key+0x75/0x280 >> [] ? __build_all_zonelists+0x0/0x5d0 >> [] stop_machine_create+0x3a/0xb0 >> [] stop_machine+0x27/0x60 >> [] build_all_zonelists+0xd0/0x2b0 >> [] cpu_up+0xb3/0xe3 >> [] store_online+0x70/0xa0 >> [] sysdev_store+0x20/0x30 >> [] sysfs_write_file+0xe5/0x170 >> [] vfs_write+0xb8/0x1a0 >> [] ? audit_syscall_entry+0x252/0x280 >> [] sys_write+0x51/0x90 >> [] system_call_fastpath+0x16/0x1b >> Built 4 zonelists in Zone order, mobility grouping on. Total pages: 123= 31603 >> PERCPU: allocation failed, size=3D128 align=3D64, failed to populate >> >> With "enable CPU to online before memory" patch, when the 1st CPU of >> an offlined node is being onlined, we build zonelists for that node. >> If per-cpu area needs to be extended during zonelists building period, >> alloc_pages_node() will be called. The routine alloc_pages_node() fails >> on the node in-onlining because the node doesn't have zonelists created >> yet. >> >> To fix this issue, we try to alloc memory from current node. > >How serious is this issue? Just a warning? Dead box? > >Because if we want to port this fix into 2.6.34.x, we have a little >problem. when onlining CPU within a node without local memory , at that time, if per-cpu-area were used up and failed to be extended, there will be many warnings about the failure of pcpu_allco(), and at last, an out-of-memory= =20 is triggered and some processes get killed by OOM. -minskey > > >> --- a/mm/percpu.c >> +++ b/mm/percpu.c >> @@ -714,13 +714,29 @@ static int pcpu_alloc_pages(struct pcpu_chunk >*chunk, > >In linux-next, Tejun has gone and moved pcpu_alloc_pages() into the new >mm/percpu-vm.c. So either > >a) the -stable guys will need to patch a different file or > >b) we apply this fix first and muck up Tejun's tree or > >c) the bug isn't very serious so none of this applies. > >> { >> const gfp_t gfp =3D GFP_KERNEL | __GFP_HIGHMEM | __GFP_COLD; >> unsigned int cpu; >> + int nid; >> int i; >> >> for_each_possible_cpu(cpu) { >> for (i =3D page_start; i < page_end; i++) { >> struct page **pagep =3D &pages[pcpu_page_idx(cpu, i)]; >> >> - *pagep =3D alloc_pages_node(cpu_to_node(cpu), gfp, 0); >> + nid =3D cpu_to_node(cpu); >> + >> + /* >> + * It is allowable to online a CPU within a NUMA >> + * node which doesn't have onlined local memory. >> + * In this case, we need to create zonelists for >> + * that node when cpu is being onlined. If per-cpu >> + * area needs to be extended at the exact time when >> + * zonelists of that node is being created, we alloc >> + * memory from current node. >> + */ >> + if ((nid =3D=3D -1) || >> + !(node_zonelist(nid, GFP_KERNEL)->_zonerefs->zone)) >> + nid =3D numa_node_id(); >> + >> + *pagep =3D alloc_pages_node(nid, gfp, 0); >> if (!*pagep) { >> pcpu_free_pages(chunk, pages, populated, >> page_start, page_end); -- 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