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Date: Wed, 14 Oct 2015 18:18:30 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Changsheng Liu <liuchangsheng@...pur.com>,
akpm@...ux-foundation.org, isimatu.yasuaki@...fujitsu.com,
yasu.isimatu@...il.com, tangchen@...fujitsu.com
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
wangnan0@...wei.com, dave.hansen@...el.com, yinghai@...nel.org,
toshi.kani@...com, qiuxishi@...wei.com, wunan@...pur.com,
yanxiaofeng@...pur.com, fandd@...pur.com,
Changsheng Liu <liuchangcheng@...pur.com>
Subject: Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable
zone defaultly
On 10/12/2015 08:58 AM, Changsheng Liu wrote:
> From: Changsheng Liu <liuchangcheng@...pur.com>
>
> After the user config CONFIG_MOVABLE_NODE,
> When the memory is hot added, should_add_memory_movable() return 0
> because all zones including ZONE_MOVABLE are empty,
> so the memory that was hot added will be assigned to ZONE_NORMAL
> and ZONE_NORMAL will be created firstly.
> But we want the whole node to be added to ZONE_MOVABLE by default.
>
> So we change should_add_memory_movable(): if the user config
> CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable is 1
> and the ZONE_NORMAL is empty or the pfn of the hot-added memory
> is after the end of the ZONE_NORMAL it will always return 1
> and then the whole node will be added to ZONE_MOVABLE by default.
> If we want the node to be assigned to ZONE_NORMAL,
> we can do it as follows:
> "echo online_kernel > /sys/devices/system/memory/memoryXXX/state"
>
> By the patch, the behavious of kernel is changed by sysctl,
> user can automatically create movable memory
> by only the following udev rule:
> SUBSYSTEM=="memory", ACTION=="add",
> ATTR{state}=="offline", ATTR{state}="online"
So just to be clear, we are adding a new sysctl, because the existing
movable_node kernel option, which is checked by movable_node_is_enabled(), and
does the same thing for non-hot-added-memory (?) cannot be reused for hot-added
memory, as that would be a potentially surprising behavior change? Correct? Then
this should be mentioned in the changelog too, and wherever "movable_node" is
documented should also mention the new sysctl. Personally, I would expect
movable_node to affect hot-added memory as well, and would be surprised that it
doesn't...
> Signed-off-by: Changsheng Liu <liuchangsheng@...pur.com>
> Signed-off-by: Xiaofeng Yan <yanxiaofeng@...pur.com>
> Tested-by: Dongdong Fan <fandd@...pur.com>
> Cc: Wang Nan <wangnan0@...wei.com>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Yinghai Lu <yinghai@...nel.org>
> Cc: Tang Chen <tangchen@...fujitsu.com>
> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
> Cc: Toshi Kani <toshi.kani@...com>
> Cc: Xishi Qiu <qiuxishi@...wei.com>
> ---
> Documentation/memory-hotplug.txt | 5 ++++-
> kernel/sysctl.c | 15 +++++++++++++++
> mm/memory_hotplug.c | 24 ++++++++++++++++++++++++
> 3 files changed, 43 insertions(+), 1 deletions(-)
>
> diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
> index ce2cfcf..7ac7485 100644
> --- a/Documentation/memory-hotplug.txt
> +++ b/Documentation/memory-hotplug.txt
> @@ -277,7 +277,7 @@ And if the memory block is in ZONE_MOVABLE, you can change it to ZONE_NORMAL:
> 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).
> +Currently, newly added memory is added as ZONE_NORMAL or ZONE_MOVABLE (for powerpc, ZONE_DMA).
> This may be changed in future.
>
>
> @@ -319,6 +319,9 @@ creates ZONE_MOVABLE as following.
> Size of memory not for movable pages (not for offline) is TOTAL - ZZZZ.
> Size of memory for movable pages (for offline) is ZZZZ.
>
> +And a sysctl parameter for assigning the hot added memory to ZONE_MOVABLE is
> +supported. If the value of "kernel/hotadd_memory_as_movable" is 1,the hot added
> +memory will be assigned to ZONE_MOVABLE by default.
>
> Note: Unfortunately, there is no information to show which memory block belongs
> to ZONE_MOVABLE. This is TBD.
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 19b62b5..16b1501 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -166,6 +166,10 @@ extern int unaligned_dump_stack;
> extern int no_unaligned_warning;
> #endif
>
> +#ifdef CONFIG_MOVABLE_NODE
> +extern int hotadd_memory_as_movable;
> +#endif
> +
> #ifdef CONFIG_PROC_SYSCTL
>
> #define SYSCTL_WRITES_LEGACY -1
> @@ -1139,6 +1143,17 @@ static struct ctl_table kern_table[] = {
> .proc_handler = timer_migration_handler,
> },
> #endif
> +/*If the value of "kernel/hotadd_memory_as_movable" is 1,the hot added
> + * memory will be assigned to ZONE_MOVABLE by default.*/
> +#ifdef CONFIG_MOVABLE_NODE
> + {
> + .procname = "hotadd_memory_as_movable",
> + .data = &hotadd_memory_as_movable,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = proc_dointvec,
> + },
> +#endif
> { }
> };
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 26fbba7..eca5512 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -37,6 +37,11 @@
>
> #include "internal.h"
>
> +/*If the global variable value is 1,
> + * the hot added memory will be assigned to ZONE_MOVABLE by default
> + */
> +int hotadd_memory_as_movable;
> +
> /*
> * online_page_callback contains pointer to current page onlining function.
> * Initially it is generic_online_page(). If it is required it could be
> @@ -1190,6 +1195,9 @@ static int check_hotplug_memory_range(u64 start, u64 size)
> /*
> * If movable zone has already been setup, newly added memory should be check.
> * If its address is higher than movable zone, it should be added as movable.
> + * And if system config CONFIG_MOVABLE_NODE and set the sysctl parameter
> + * "hotadd_memory_as_movable" and added memory does not overlap the zone
> + * before MOVABLE_ZONE,the memory will be added as movable.
> * Without this check, movable zone may overlap with other zone.
> */
> static int should_add_memory_movable(int nid, u64 start, u64 size)
> @@ -1197,6 +1205,22 @@ static int should_add_memory_movable(int nid, u64 start, u64 size)
> unsigned long start_pfn = start >> PAGE_SHIFT;
> pg_data_t *pgdat = NODE_DATA(nid);
> struct zone *movable_zone = pgdat->node_zones + ZONE_MOVABLE;
> + struct zone *pre_zone = pgdat->node_zones + (ZONE_MOVABLE - 1);
> + /*
> + * The system configs CONFIG_MOVABLE_NODE to assign a node
> + * which has only movable memory,so the hot-added memory should
> + * be assigned to ZONE_MOVABLE by default,
> + * but the function zone_for_memory() assign the hot-added memory
> + * to ZONE_NORMAL(x86_64) by default.Kernel does not allow to
> + * create ZONE_MOVABLE before ZONE_NORMAL,So if the value of
> + * sysctl parameter "hotadd_memory_as_movable" is 1
> + * and the ZONE_NORMAL is empty or the pfn of the hot-added memory
> + * is after the end of ZONE_NORMAL
> + * the hot-added memory will be assigned to ZONE_MOVABLE.
> + */
> + if (hotadd_memory_as_movable
> + && (zone_is_empty(pre_zone) || zone_end_pfn(pre_zone) <= start_pfn))
> + return 1;
>
> if (zone_is_empty(movable_zone))
> return 0;
>
--
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