From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kamezawa Hiroyuki Date: Wed, 26 Dec 2012 03:02:00 +0000 Subject: Re: [PATCH v5 01/14] memory-hotplug: try to offline the memory twice to avoid dependence Message-Id: <50DA68A8.4060001@jp.fujitsu.com> List-Id: References: <1356350964-13437-1-git-send-email-tangchen@cn.fujitsu.com> <1356350964-13437-2-git-send-email-tangchen@cn.fujitsu.com> In-Reply-To: <1356350964-13437-2-git-send-email-tangchen@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tang Chen Cc: akpm@linux-foundation.org, rientjes@google.com, liuj97@gmail.com, len.brown@intel.com, benh@kernel.crashing.org, paulus@samba.org, cl@linux.com, minchan.kim@gmail.com, kosaki.motohiro@jp.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, wujianguo@huawei.com, wency@cn.fujitsu.com, hpa@zytor.com, linfeng@cn.fujitsu.com, laijs@cn.fujitsu.com, mgorman@suse.de, yinghai@kernel.org, x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-ia64@vger.kernel.org, cmetcalf@tilera.com, sparclinux@vger.kernel.org (2012/12/24 21:09), Tang Chen wrote: > From: Wen Congyang > > 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. > If memory8 is onlined as NORMAL memory ...right ? IIUC, vmalloc() uses __GFP_HIGHMEM but doesn't use __GFP_MOVABLE. > 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 I'm not sure but the whole DIMM should be onlined as MOVABLE mem ? Anyway, I agree this kind of retry is required if memory is onlined as NORMAL mem. But retry-once is ok ? Thanks, -Kame > --- > mm/memory_hotplug.c | 16 ++++++++++++++-- > 1 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index d04ed87..62e04c9 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1388,10 +1388,13 @@ int remove_memory(u64 start, u64 size) > unsigned long start_pfn, end_pfn; > unsigned long pfn, section_nr; > int ret; > + int return_on_error = 0; > + int retry = 0; > > start_pfn = PFN_DOWN(start); > end_pfn = start_pfn + PFN_DOWN(size); > > +repeat: > for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) { > section_nr = pfn_to_section_nr(pfn); > if (!present_section_nr(section_nr)) > @@ -1410,14 +1413,23 @@ int remove_memory(u64 start, u64 size) > > ret = offline_memory_block(mem); > if (ret) { > - kobject_put(&mem->dev.kobj); > - return ret; > + if (return_on_error) { > + kobject_put(&mem->dev.kobj); > + return ret; > + } else { > + retry = 1; > + } > } > } > > if (mem) > kobject_put(&mem->dev.kobj); > > + if (retry) { > + return_on_error = 1; > + goto repeat; > + } > + > return 0; > } > #else >