From: Glauber Costa <glommer@parallels.com>
To: Tang Chen <tangchen@cn.fujitsu.com>
Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
linux-mm@kvack.org, paulus@samba.org, hpa@zytor.com,
sparclinux@vger.kernel.org, cl@linux.com,
linux-s390@vger.kernel.org, x86@kernel.org,
linux-acpi@vger.kernel.org, isimatu.yasuaki@jp.fujitsu.com,
linfeng@cn.fujitsu.com, mgorman@suse.de,
kosaki.motohiro@jp.fujitsu.com, rientjes@google.com,
liuj97@gmail.com, len.brown@intel.com, wency@cn.fujitsu.com,
cmetcalf@tilera.com, wujianguo@huawei.com, yinghai@kernel.org,
laijs@cn.fujitsu.com, linux-kernel@vger.kernel.org,
minchan.kim@gmail.com, akpm@linux-foundation.org,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v5 01/14] memory-hotplug: try to offline the memory twice to avoid dependence
Date: Tue, 25 Dec 2012 12:35:15 +0400 [thread overview]
Message-ID: <50D96543.6010903@parallels.com> (raw)
In-Reply-To: <1356350964-13437-2-git-send-email-tangchen@cn.fujitsu.com>
On 12/24/2012 04:09 PM, Tang Chen wrote:
> From: Wen Congyang <wency@cn.fujitsu.com>
>
> memory can't be offlined when CONFIG_MEMCG is selected.
> For example: there is a memory device on node 1. The address range
> is [1G, 1.5G). You will find 4 new directories memory8, memory9, memory10,
> and memory11 under the directory /sys/devices/system/memory/.
>
> If CONFIG_MEMCG is selected, we will allocate memory to store page cgroup
> when we online pages. When we online memory8, the memory stored page cgroup
> is not provided by this memory device. But when we online memory9, the memory
> stored page cgroup may be provided by memory8. So we can't offline memory8
> now. We should offline the memory in the reversed order.
>
> When the memory device is hotremoved, we will auto offline memory provided
> by this memory device. But we don't know which memory is onlined first, so
> offlining memory may fail. In such case, iterate twice to offline the memory.
> 1st iterate: offline every non primary memory block.
> 2nd iterate: offline primary (i.e. first added) memory block.
>
> This idea is suggested by KOSAKI Motohiro.
>
> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Maybe there is something here that I am missing - I admit that I came
late to this one, but this really sounds like a very ugly hack, that
really has no place in here.
Retrying, of course, may make sense, if we have reasonable belief that
we may now succeed. If this is the case, you need to document - in the
code - while is that.
The memcg argument, however, doesn't really cut it. Why can't we make
all page_cgroup allocations local to the node they are describing? If
memcg is the culprit here, we should fix it, and not retry. If there is
still any benefit in retrying, then we retry being very specific about why.
next prev parent reply other threads:[~2012-12-25 8:48 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-24 12:09 [PATCH v5 00/14] memory-hotplug: hot-remove physical memory Tang Chen
2012-12-24 12:09 ` [PATCH v5 01/14] memory-hotplug: try to offline the memory twice to avoid dependence Tang Chen
2012-12-25 8:35 ` Glauber Costa [this message]
2012-12-30 5:58 ` Wen Congyang
2013-01-09 15:09 ` Glauber Costa
2013-01-10 1:38 ` Tang Chen
2013-02-06 3:07 ` Tang Chen
2013-02-06 9:17 ` Tang Chen
2013-02-06 10:10 ` Tang Chen
2013-02-06 14:24 ` Glauber Costa
2013-02-07 7:56 ` Tang Chen
2012-12-26 3:02 ` Kamezawa Hiroyuki
2012-12-30 5:49 ` Wen Congyang
2012-12-24 12:09 ` [PATCH v5 02/14] memory-hotplug: check whether all memory blocks are offlined or not when removing memory Tang Chen
2012-12-26 3:10 ` Kamezawa Hiroyuki
2012-12-27 3:10 ` Tang Chen
2012-12-24 12:09 ` [PATCH v5 03/14] memory-hotplug: remove redundant codes Tang Chen
2012-12-26 3:20 ` Kamezawa Hiroyuki
2012-12-27 3:09 ` Tang Chen
2012-12-24 12:09 ` [PATCH v5 04/14] memory-hotplug: remove /sys/firmware/memmap/X sysfs Tang Chen
2012-12-26 3:30 ` Kamezawa Hiroyuki
2012-12-27 3:09 ` Tang Chen
2013-01-02 14:24 ` Christoph Lameter
2012-12-24 12:09 ` [PATCH v5 05/14] memory-hotplug: introduce new function arch_remove_memory() for removing page table depends on architecture Tang Chen
2012-12-26 3:37 ` Kamezawa Hiroyuki
2012-12-24 12:09 ` [PATCH v5 06/14] memory-hotplug: implement register_page_bootmem_info_section of sparse-vmemmap Tang Chen
2012-12-25 8:09 ` Jianguo Wu
2012-12-26 3:21 ` Tang Chen
2012-12-24 12:09 ` [PATCH v5 07/14] memory-hotplug: move pgdat_resize_lock into sparse_remove_one_section() Tang Chen
2012-12-26 3:47 ` Kamezawa Hiroyuki
2012-12-26 6:20 ` Tang Chen
2012-12-24 12:09 ` [PATCH v5 08/14] memory-hotplug: Common APIs to support page tables hot-remove Tang Chen
2012-12-25 8:17 ` Jianguo Wu
2012-12-26 2:49 ` Tang Chen
2012-12-26 3:11 ` Tang Chen
2012-12-26 3:19 ` Tang Chen
2012-12-24 12:09 ` [PATCH v5 09/14] memory-hotplug: remove page table of x86_64 architecture Tang Chen
2012-12-24 12:09 ` [PATCH v5 10/14] memory-hotplug: remove memmap of sparse-vmemmap Tang Chen
2012-12-24 12:09 ` [PATCH v5 11/14] memory-hotplug: Integrated __remove_section() of CONFIG_SPARSEMEM_VMEMMAP Tang Chen
2012-12-24 12:09 ` [PATCH v5 12/14] memory-hotplug: memory_hotplug: clear zone when removing the memory Tang Chen
2012-12-24 12:09 ` [PATCH v5 13/14] memory-hotplug: remove sysfs file of node Tang Chen
2012-12-24 12:09 ` [PATCH v5 14/14] memory-hotplug: free node_data when a node is offlined Tang Chen
2012-12-26 3:55 ` Kamezawa Hiroyuki
2012-12-27 12:16 ` Wen Congyang
2012-12-28 0:28 ` Kamezawa Hiroyuki
2012-12-30 6:02 ` Wen Congyang
2013-01-07 5:30 ` Kamezawa Hiroyuki
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