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Message-ID: <561803bc.92c38c0a.c7a5b.5820@mx.google.com>
Date: Fri, 09 Oct 2015 11:13:16 -0700 (PDT)
From: Yasuaki Ishimatsu <yasu.isimatu@...il.com>
To: Tang Chen <tangchen@...fujitsu.com>
Cc: Changsheng Liu <liuchangsheng@...pur.com>,
<akpm@...ux-foundation.org>, <isimatu.yasuaki@...fujitsu.com>,
<vbabka@...e.cz>, <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 V6] mm: memory hot-add: memory can not be added to
movable zone defaultly
Hi Tang,
On Fri, 9 Oct 2015 15:59:38 +0800
Tang Chen <tangchen@...fujitsu.com> wrote:
> Hi,
>
> I don't mean to offend, but I really think it is not necessary to do this.
>
> hot-added memory will be added to ZONE_NORMAL by default. You can
> modify it when you online memory. I think it is enough for users.
But we cannot automatically create movable memory even if we use udev rules.
Thus user must create original scrip to online memory as movable.
Do you think every user understand the rule that ZONE_NORMAL must be on the
left side of ZONE_MOVABLE?
If we can change the behavir of kernel by sysctl, user can create
movable memory by only the following udev rule.
SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", ATTR{state}="online"
Thanks,
Yasuaki Ishimatsu
>
> And a sysctl interface is also unnecessary. I think one default behaviour
> is enough for kernel. We'd better keep it in the current way, or change it
> and document it. It just makes no sense to enable users to modify it.
> Can you please share any use case of this sysctl interface ?
>
> I suggest just keep the current implement. But I'm OK with that if other
> reviewers or users could clarify it is useful. :)
>
> And BTW, please don't cc the following reviewers. Their email addresses
> have changed.
>
> Cc: Zhang Yanfei<zhangyanfei@...fujitsu.com>
> Cc: Hu Tao<hutao@...fujitsu.com>
> Cc: Lai Jiangshan<laijs@...fujitsu.com>
> Cc: Gu Zheng<guz.fnst@...fujitsu.com>
>
>
> Thanks. :)
>
> On 10/09/2015 03:12 PM, 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 movable zone are empty,
> > so the memory that was hot added will be added to the normal zone
> > and the normal zone will be created firstly.
> > But we want the whole node to be added to movable zone defaultly.
> >
> > So we change should_add_memory_movable(): if the user config
> > CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable 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 all zones is empty at the same time,
> > so that the movable zone will be created firstly
> > and then the whole node will be added to movable zone defaultly.
> > If we want the node to be added to normal zone,
> > we can do it as follows:
> > "echo online_kernel > /sys/devices/system/memory/memoryXXX/state"
> >
> > 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: Zhang Yanfei <zhangyanfei@...fujitsu.com>
> > Cc: Dave Hansen <dave.hansen@...el.com>
> > Cc: Yinghai Lu <yinghai@...nel.org>
> > Cc: Tang Chen <tangchen@...fujitsu.com>
> > Cc: Hu Tao <hutao@...fujitsu.com>
> > Cc: Lai Jiangshan <laijs@...fujitsu.com>
> > Cc: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
> > Cc: Gu Zheng <guz.fnst@...fujitsu.com>
> > Cc: Toshi Kani <toshi.kani@...com>
> > Cc: Xishi Qiu <qiuxishi@...wei.com>
> > Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> > ---
> > Documentation/memory-hotplug.txt | 5 ++++-
> > kernel/sysctl.c | 15 +++++++++++++++
> > mm/memory_hotplug.c | 23 +++++++++++++++++++++++
> > 3 files changed, 42 insertions(+), 1 deletions(-)
> >
> > diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
> > index ce2cfcf..7e6b4f4 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 defautly.
> >
> > 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..855c48e 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 defautly.*/
> > +#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..5bcaf74 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -37,6 +37,10 @@
> >
> > #include "internal.h"
> >
> > +/*If the global variable value is 1,
> > + * the hot added memory will be assigned to ZONE_MOVABLE defautly*/
> > +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 +1194,9 @@ 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 is 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 +1204,22 @@ 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 defaultly,
> > + * but the function zone_for_memory() assign the hot-added memory
> > + * to ZONE_NORMAL(x86_64) defaultly.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 the 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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