Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934110AbaDJBEY (ORCPT ); Wed, 9 Apr 2014 21:04:24 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:45275 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S932996AbaDJBEX (ORCPT ); Wed, 9 Apr 2014 21:04:23 -0400 X-IronPort-AV: E=Sophos;i="4.97,830,1389715200"; d="scan'208";a="29069902" Message-ID: <5345EDCC.2000900@cn.fujitsu.com> Date: Thu, 10 Apr 2014 09:03:08 +0800 From: Zhang Yanfei User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131030 Thunderbird/17.0.10 MIME-Version: 1.0 To: Nathan Fontenot CC: Dave Hansen , Li Zhong , Yasuaki Ishimatsu , LKML , , Andrew Morton , KAMEZAWA Hiroyuki , KOSAKI Motohiro Subject: Re: [RFC PATCH] memory driver: make phys_index/end_phys_index reflect the start/end section number References: <1396429018.2913.19.camel@ThinkPad-T5421.cn.ibm.com> <533E0B0E.9020909@jp.fujitsu.com> <1396945659.3162.6.camel@ThinkPad-T5421.cn.ibm.com> <53442021.2060608@intel.com> <53443E8C.4070906@linux.vnet.ibm.com> <53445245.3020400@intel.com> <534585E8.50302@linux.vnet.ibm.com> In-Reply-To: <534585E8.50302@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.167.226.197] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/10/2014 01:39 AM, Nathan Fontenot wrote: > On 04/08/2014 02:47 PM, Dave Hansen wrote: >> >> That document really needs to be updated to stop referring to sections >> (at least in the descriptions of the user interface). We can not change >> the units of phys_index/end_phys_index without also changing >> block_size_bytes. >> > > Here is a first pass at updating the documentation. > > I have tried to update the documentation to refer to memory blocks instead > of memory sections where appropriate and added a paragraph to explain > that memory blocks are mode of memory sections. > > Thoughts? I think the change is basically ok. So Reviewed-by: Zhang Yanfei Only one nitpick below. > > -Nathan > --- > Documentation/memory-hotplug.txt | 113 ++++++++++++++++++++------------------- > 1 file changed, 59 insertions(+), 54 deletions(-) > > Index: linux/Documentation/memory-hotplug.txt > =================================================================== > --- linux.orig/Documentation/memory-hotplug.txt > +++ linux/Documentation/memory-hotplug.txt > @@ -88,16 +88,21 @@ phase by hand. > > 1.3. Unit of Memory online/offline operation > ------------ > -Memory hotplug uses SPARSEMEM memory model. SPARSEMEM divides the whole memory > -into chunks of the same size. The chunk is called a "section". The size of > -a section is architecture dependent. For example, power uses 16MiB, ia64 uses > -1GiB. The unit of online/offline operation is "one section". (see Section 3.) > +Memory hotplug uses SPARSEMEM memory model which allows memory to be divided > +into chunks of the same size. These chunks are called "sections". The size of > +a memory section is architecture dependent. For example, power uses 16MiB, ia64 > +uses 1GiB. > + > +Memory sections are combined into chunks referred to as "memory blocks". The > +size of a memory block is architecture dependent and represents the logical > +unit upon which memory online/offline operations are to be performed. The > +default size of a memory block is the same as memory section size unless an > +architecture specifies otherwise. (see Section 3.) > > -To determine the size of sections, please read this file: > +To determine the size (in bytes) of a memory block please read this file: > > /sys/devices/system/memory/block_size_bytes > > -This file shows the size of sections in byte. > > ----------------------- > 2. Kernel Configuration > @@ -123,14 +128,15 @@ config options. > (CONFIG_ACPI_CONTAINER). > This option can be kernel module too. > > + > -------------------------------- > -4 sysfs files for memory hotplug > +3 sysfs files for memory hotplug > -------------------------------- > -All sections have their device information in sysfs. Each section is part of > -a memory block under /sys/devices/system/memory as > +All memory blocks have their device information in sysfs. Each memory block > +is described under /sys/devices/system/memory as > > /sys/devices/system/memory/memoryXXX > -(XXX is the section id.) > +(XXX is the memory block id.) > > Now, XXX is defined as (start_address_of_section / section_size) of the first > section contained in the memory block. The files 'phys_index' and > @@ -141,13 +147,13 @@ range. Currently there is no way to dete > the existence of one should not affect the hotplug capabilities of the memory > block. > > -For example, assume 1GiB section size. A device for a memory starting at > +For example, assume 1GiB memory block size. A device for a memory starting at > 0x100000000 is /sys/device/system/memory/memory4 > (0x100000000 / 1Gib = 4) > This device covers address range [0x100000000 ... 0x140000000) > > -Under each section, you can see 4 or 5 files, the end_phys_index file being > -a recent addition and not present on older kernels. > +Under each memory block, you can see 4 or 5 files, the end_phys_index file > +being a recent addition and not present on older kernels. > > /sys/devices/system/memory/memoryXXX/start_phys_index > /sys/devices/system/memory/memoryXXX/end_phys_index > @@ -185,6 +191,7 @@ For example: > A backlink will also be created: > /sys/devices/system/memory/memory9/node0 -> ../../node/node0 > > + > -------------------------------- > 4. Physical memory hot-add phase > -------------------------------- > @@ -227,11 +234,10 @@ You can tell the physical address of new > > % echo start_address_of_new_memory > /sys/devices/system/memory/probe > > -Then, [start_address_of_new_memory, start_address_of_new_memory + section_size) > -memory range is hot-added. In this case, hotplug script is not called (in > -current implementation). You'll have to online memory by yourself. > -Please see "How to online memory" in this text. > - > +Then, [start_address_of_new_memory, start_address_of_new_memory + > +memory_block_size] memory range is hot-added. In this case, hotplug script is > +not called (in current implementation). You'll have to online memory by > +yourself. Please see "How to online memory" in this text. > > > ------------------------------ > @@ -240,36 +246,36 @@ Please see "How to online memory" in thi > > 5.1. State of memory > ------------ > -To see (online/offline) state of memory section, read 'state' file. > +To see (online/offline) state of a memory block, read 'state' file. > > % cat /sys/device/system/memory/memoryXXX/state > > > -If the memory section is online, you'll read "online". > -If the memory section is offline, you'll read "offline". > +If the memory block is online, you'll read "online". > +If the memory block is offline, you'll read "offline". > > > 5.2. How to online memory > ------------ > Even if the memory is hot-added, it is not at ready-to-use state. > -For using newly added memory, you have to "online" the memory section. > +For using newly added memory, you have to "online" the memory block. > > -For onlining, you have to write "online" to the section's state file as: > +For onlining, you have to write "online" to the memory block's state file as: > > % echo online > /sys/devices/system/memory/memoryXXX/state > > -This onlining will not change the ZONE type of the target memory section, > -If the memory section is in ZONE_NORMAL, you can change it to ZONE_MOVABLE: > +This onlining will not change the ZONE type of the target memory block, > +If the memory block is in ZONE_NORMAL, you can change it to ZONE_MOVABLE: > > % echo online_movable > /sys/devices/system/memory/memoryXXX/state > -(NOTE: current limit: this memory section must be adjacent to ZONE_MOVABLE) > +(NOTE: current limit: this memory block must be adjacent to ZONE_MOVABLE) > > -And if the memory section is in ZONE_MOVABLE, you can change it to ZONE_NORMAL: > +And if the memory block is in ZONE_MOVABLE, you can change it to ZONE_NORMAL: > > % echo online_kernel > /sys/devices/system/memory/memoryXXX/state > -(NOTE: current limit: this memory section must be adjacent to ZONE_NORMAL) > +(NOTE: current limit: this memory block must be adjacent to ZONE_NORMAL) > > -After this, section memoryXXX's state will be 'online' and the amount of > +After this, memory block XXX's state will be 'online' and the amount of > available memory will be increased. > > Currently, newly added memory is added as ZONE_NORMAL (for powerpc, ZONE_DMA). > @@ -284,22 +290,22 @@ This may be changed in future. > 6.1 Memory offline and ZONE_MOVABLE > ------------ > Memory offlining is more complicated than memory online. Because memory offline > -has to make the whole memory section be unused, memory offline can fail if > -the section includes memory which cannot be freed. > +has to make the whole memory block be unused, memory offline can fail if > +the memort block includes memory which cannot be freed. ^^^^^^ memory > > In general, memory offline can use 2 techniques. > > -(1) reclaim and free all memory in the section. > -(2) migrate all pages in the section. > +(1) reclaim and free all memory in the memory block. > +(2) migrate all pages in the memory block. > > In the current implementation, Linux's memory offline uses method (2), freeing > -all pages in the section by page migration. But not all pages are > +all pages in the memory block by page migration. But not all pages are > migratable. Under current Linux, migratable pages are anonymous pages and > -page caches. For offlining a section by migration, the kernel has to guarantee > -that the section contains only migratable pages. > +page caches. For offlining a memory block by migration, the kernel has to > +guarantee that the memory block contains only migratable pages. > > -Now, a boot option for making a section which consists of migratable pages is > -supported. By specifying "kernelcore=" or "movablecore=" boot option, you can > +Now, a boot option for making a memory block which consists of migratable pages > +is supported. By specifying "kernelcore=" or "movablecore=" boot option, you can > create ZONE_MOVABLE...a zone which is just used for movable pages. > (See also Documentation/kernel-parameters.txt) > > @@ -315,28 +321,27 @@ creates ZONE_MOVABLE as following. > Size of memory for movable pages (for offline) is ZZZZ. > > > -Note) Unfortunately, there is no information to show which section belongs > +Note: Unfortunately, there is no information to show which memory block belongs > to ZONE_MOVABLE. This is TBD. > > > 6.2. How to offline memory > ------------ > -You can offline a section by using the same sysfs interface that was used in > -memory onlining. > +You can offline a memory block by using the same sysfs interface that was used > +in memory onlining. > > % echo offline > /sys/devices/system/memory/memoryXXX/state > > -If offline succeeds, the state of the memory section is changed to be "offline". > +If offline succeeds, the state of the memory block is changed to be "offline". > If it fails, some error core (like -EBUSY) will be returned by the kernel. > -Even if a section does not belong to ZONE_MOVABLE, you can try to offline it. > -If it doesn't contain 'unmovable' memory, you'll get success. > +Even if a memory block does not belong to ZONE_MOVABLE, you can try to offline > +it. If it doesn't contain 'unmovable' memory, you'll get success. > > -A section under ZONE_MOVABLE is considered to be able to be offlined easily. > -But under some busy state, it may return -EBUSY. Even if a memory section > -cannot be offlined due to -EBUSY, you can retry offlining it and may be able to > -offline it (or not). > -(For example, a page is referred to by some kernel internal call and released > - soon.) > +A memory block under ZONE_MOVABLE is considered to be able to be offlined > +easily. But under some busy state, it may return -EBUSY. Even if a memory > +block cannot be offlined due to -EBUSY, you can retry offlining it and may be > +able to offline it (or not). (For example, a page is referred to by some kernel > +internal call and released soon.) > > Consideration: > Memory hotplug's design direction is to make the possibility of memory offlining > @@ -373,11 +378,11 @@ MEMORY_GOING_OFFLINE > Generated to begin the process of offlining memory. Allocations are no > longer possible from the memory but some of the memory to be offlined > is still in use. The callback can be used to free memory known to a > - subsystem from the indicated memory section. > + subsystem from the indicated memory block. > > MEMORY_CANCEL_OFFLINE > Generated if MEMORY_GOING_OFFLINE fails. Memory is available again from > - the section that we attempted to offline. > + the memory block that we attempted to offline. > > MEMORY_OFFLINE > Generated after offlining memory is complete. > @@ -413,8 +418,8 @@ node if necessary. > -------------- > - allowing memory hot-add to ZONE_MOVABLE. maybe we need some switch like > sysctl or new control file. > - - showing memory section and physical device relationship. > - - showing memory section is under ZONE_MOVABLE or not > + - showing memory block and physical device relationship. > + - showing memory block is under ZONE_MOVABLE or not > - test and make it better memory offlining. > - support HugeTLB page migration and offlining. > - memmap removing at memory offline. > > . > -- Thanks. 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