There are two problems when calculating node meminfo:
1. When hot-adding a node without onlining any page, MemTotal corrupted.
# hot-add node2 (memory not onlined)
# cat /sys/device/system/node/node2/meminfo
Node 2 MemTotal: 33554432 kB /* corrupted */
Node 2 MemFree: 0 kB
Node 2 MemUsed: 33554432 kB
Node 2 Active: 0 kB
......
2. When onlining memory on node2, MemFree of node3 corrupted.
# for ((i = 2048; i < 2064; i++)); do echo online_movable > /sys/devices/system/node/node2/memory$i/state; done
# cat /sys/devices/system/node/node2/meminfo
Node 2 MemTotal: 33554432 kB
Node 2 MemFree: 33549092 kB
Node 2 MemUsed: 5340 kB
......
# cat /sys/devices/system/node/node3/meminfo
Node 3 MemTotal: 0 kB
Node 3 MemFree: 248 kB /* corrupted */
Node 3 MemUsed: 0 kB
......
This patch-set fixes them.
Tang Chen (2):
mem-hotplug: Reset node managed pages when hot-adding a new pgdat.
mem-hotplug: Fix wrong check for zone->pageset initialization in
online_pages().
include/linux/bootmem.h | 1 +
include/linux/mm.h | 1 +
mm/bootmem.c | 9 +++++----
mm/memory_hotplug.c | 15 ++++++++++++++-
mm/nobootmem.c | 8 +++++---
mm/page_alloc.c | 5 +++++
6 files changed, 31 insertions(+), 8 deletions(-)
--
1.8.3.1
When we are doing memory hot-add, the following functions are called:
add_memory()
|--> hotadd_new_pgdat()
|--> free_area_init_node()
|--> free_area_init_core()
|--> zone->present_pages = realsize; /* 1. zone is populated */
|--> zone_pcp_init()
|--> zone->pageset = &boot_pageset; /* 2. zone->pageset is set to boot_pageset */
There are two problems here:
1. Zones could be populated before any memory is onlined.
2. All the zones on a newly added node have the same pageset pointing to boot_pageset.
The above two problems will result in the following problem:
When we online memory on one node, e.g node2, the following code is executed:
online_pages()
{
......
if (!populated_zone(zone)) {
need_zonelists_rebuild = 1;
build_all_zonelists(NULL, zone);
}
......
}
Because of problem 1, the zone has been populated, and the build_all_zonelists()
will never called. zone->pageset won't be updated.
Because of problem 2, All the zones on a newly added node have the same pageset
pointing to boot_pageset.
And as a result, when we online memory on node2, node3's meminfo will corrupt.
Pages on node2 may be freed to node3.
# for ((i = 2048; i < 2064; i++)); do echo online_movable > /sys/devices/system/node/node2/memory$i/state; done
# cat /sys/devices/system/node/node2/meminfo
Node 2 MemTotal: 33554432 kB
Node 2 MemFree: 33549092 kB
Node 2 MemUsed: 5340 kB
......
# cat /sys/devices/system/node/node3/meminfo
Node 3 MemTotal: 0 kB
Node 3 MemFree: 248 kB /* corrupted */
Node 3 MemUsed: 0 kB
......
We have to populate some zones before onlining memory, otherwise no memory could be onlined.
So when onlining pages, we should also check if zone->pageset is pointing to boot_pageset.
Signed-off-by: Gu Zheng <[email protected]>
Signed-off-by: Tang Chen <[email protected]>
---
include/linux/mm.h | 1 +
mm/memory_hotplug.c | 6 +++++-
mm/page_alloc.c | 5 +++++
3 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 02d11ee..83e6505 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1732,6 +1732,7 @@ void warn_alloc_failed(gfp_t gfp_mask, int order, const char *fmt, ...);
extern void setup_per_cpu_pageset(void);
+extern bool zone_pcp_initialized(struct zone *zone);
extern void zone_pcp_update(struct zone *zone);
extern void zone_pcp_reset(struct zone *zone);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 3ab01b2..bc0de0f 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1013,9 +1013,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
* If this zone is not populated, then it is not in zonelist.
* This means the page allocator ignores this zone.
* So, zonelist must be updated after online.
+ *
+ * If this zone is populated, zone->pageset could be initialized
+ * to boot_pageset for the first time a node is added. If so,
+ * zone->pageset should be allocated.
*/
mutex_lock(&zonelists_mutex);
- if (!populated_zone(zone)) {
+ if (!populated_zone(zone) || !zone_pcp_initialized(zone)) {
need_zonelists_rebuild = 1;
build_all_zonelists(NULL, zone);
}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 736d8e1..4ff1540 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6456,6 +6456,11 @@ void __meminit zone_pcp_update(struct zone *zone)
}
#endif
+bool zone_pcp_initialized(struct zone *zone)
+{
+ return (zone->pageset != &boot_pageset);
+}
+
void zone_pcp_reset(struct zone *zone)
{
unsigned long flags;
--
1.8.3.1
In free_area_init_core(), zone->managed_pages is set to an approximate
value for lowmem, and will be adjusted when the bootmem allocator frees
pages into the buddy system. But free_area_init_core() is also called
by hotadd_new_pgdat() when hot-adding memory. As a result, zone->managed_pages
of the newly added node's pgdat is set to an approximate value in the
very beginning. Even if the memory on that node has node been onlined,
/sys/device/system/node/nodeXXX/meminfo has wrong value.
hot-add node2 (memory not onlined)
cat /sys/device/system/node/node2/meminfo
Node 2 MemTotal: 33554432 kB
Node 2 MemFree: 0 kB
Node 2 MemUsed: 33554432 kB
Node 2 Active: 0 kB
This patch fixes this problem by reset node managed pages to 0 after hot-adding
a new node.
1. Move reset_managed_pages_done from reset_node_managed_pages() to reset_all_zones_managed_pages()
2. Make reset_node_managed_pages() non-static
3. Call reset_node_managed_pages() in hotadd_new_pgdat() after pgdat is initialized
Signed-off-by: Tang Chen <[email protected]>
Signed-off-by: Yasuaki Ishimatsu <[email protected]>
---
include/linux/bootmem.h | 1 +
mm/bootmem.c | 9 +++++----
mm/memory_hotplug.c | 9 +++++++++
mm/nobootmem.c | 8 +++++---
4 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
index 4e2bd4c..0995c2d 100644
--- a/include/linux/bootmem.h
+++ b/include/linux/bootmem.h
@@ -46,6 +46,7 @@ extern unsigned long init_bootmem_node(pg_data_t *pgdat,
extern unsigned long init_bootmem(unsigned long addr, unsigned long memend);
extern unsigned long free_all_bootmem(void);
+extern void reset_node_managed_pages(pg_data_t *pgdat);
extern void reset_all_zones_managed_pages(void);
extern void free_bootmem_node(pg_data_t *pgdat,
diff --git a/mm/bootmem.c b/mm/bootmem.c
index 8a000ce..477be69 100644
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -243,13 +243,10 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
static int reset_managed_pages_done __initdata;
-static inline void __init reset_node_managed_pages(pg_data_t *pgdat)
+void reset_node_managed_pages(pg_data_t *pgdat)
{
struct zone *z;
- if (reset_managed_pages_done)
- return;
-
for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
z->managed_pages = 0;
}
@@ -258,8 +255,12 @@ void __init reset_all_zones_managed_pages(void)
{
struct pglist_data *pgdat;
+ if (reset_managed_pages_done)
+ return;
+
for_each_online_pgdat(pgdat)
reset_node_managed_pages(pgdat);
+
reset_managed_pages_done = 1;
}
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 29d8693..3ab01b2 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -31,6 +31,7 @@
#include <linux/stop_machine.h>
#include <linux/hugetlb.h>
#include <linux/memblock.h>
+#include <linux/bootmem.h>
#include <asm/tlbflush.h>
@@ -1096,6 +1097,14 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
build_all_zonelists(pgdat, NULL);
mutex_unlock(&zonelists_mutex);
+ /*
+ * zone->managed_pages is set to an approximate value in
+ * free_area_init_core(), which will cause
+ * /sys/device/system/node/nodeX/meminfo has wrong data.
+ * So reset it to 0 before any memory is onlined.
+ */
+ reset_node_managed_pages(pgdat);
+
return pgdat;
}
diff --git a/mm/nobootmem.c b/mm/nobootmem.c
index 7c7ab32..90b5046 100644
--- a/mm/nobootmem.c
+++ b/mm/nobootmem.c
@@ -145,12 +145,10 @@ static unsigned long __init free_low_memory_core_early(void)
static int reset_managed_pages_done __initdata;
-static inline void __init reset_node_managed_pages(pg_data_t *pgdat)
+void reset_node_managed_pages(pg_data_t *pgdat)
{
struct zone *z;
- if (reset_managed_pages_done)
- return;
for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
z->managed_pages = 0;
}
@@ -159,8 +157,12 @@ void __init reset_all_zones_managed_pages(void)
{
struct pglist_data *pgdat;
+ if (reset_managed_pages_done)
+ return;
+
for_each_online_pgdat(pgdat)
reset_node_managed_pages(pgdat);
+
reset_managed_pages_done = 1;
}
--
1.8.3.1
Hi all,
I thinks these two problems are very important and should be merged ASAP.
Would you please help to have a look at it ?
Thanks.
On 10/31/2014 05:46 PM, Tang Chen wrote:
> There are two problems when calculating node meminfo:
>
> 1. When hot-adding a node without onlining any page, MemTotal corrupted.
>
> # hot-add node2 (memory not onlined)
> # cat /sys/device/system/node/node2/meminfo
> Node 2 MemTotal: 33554432 kB /* corrupted */
> Node 2 MemFree: 0 kB
> Node 2 MemUsed: 33554432 kB
> Node 2 Active: 0 kB
> ......
>
>
> 2. When onlining memory on node2, MemFree of node3 corrupted.
>
> # for ((i = 2048; i < 2064; i++)); do echo online_movable > /sys/devices/system/node/node2/memory$i/state; done
> # cat /sys/devices/system/node/node2/meminfo
> Node 2 MemTotal: 33554432 kB
> Node 2 MemFree: 33549092 kB
> Node 2 MemUsed: 5340 kB
> ......
> # cat /sys/devices/system/node/node3/meminfo
> Node 3 MemTotal: 0 kB
> Node 3 MemFree: 248 kB /* corrupted */
> Node 3 MemUsed: 0 kB
> ......
>
> This patch-set fixes them.
>
> Tang Chen (2):
> mem-hotplug: Reset node managed pages when hot-adding a new pgdat.
> mem-hotplug: Fix wrong check for zone->pageset initialization in
> online_pages().
>
> include/linux/bootmem.h | 1 +
> include/linux/mm.h | 1 +
> mm/bootmem.c | 9 +++++----
> mm/memory_hotplug.c | 15 ++++++++++++++-
> mm/nobootmem.c | 8 +++++---
> mm/page_alloc.c | 5 +++++
> 6 files changed, 31 insertions(+), 8 deletions(-)
>
On 2014/10/31 17:46, Tang Chen wrote:
> In free_area_init_core(), zone->managed_pages is set to an approximate
> value for lowmem, and will be adjusted when the bootmem allocator frees
> pages into the buddy system. But free_area_init_core() is also called
> by hotadd_new_pgdat() when hot-adding memory. As a result, zone->managed_pages
> of the newly added node's pgdat is set to an approximate value in the
> very beginning. Even if the memory on that node has node been onlined,
> /sys/device/system/node/nodeXXX/meminfo has wrong value.
>
> hot-add node2 (memory not onlined)
> cat /sys/device/system/node/node2/meminfo
> Node 2 MemTotal: 33554432 kB
> Node 2 MemFree: 0 kB
> Node 2 MemUsed: 33554432 kB
> Node 2 Active: 0 kB
>
> This patch fixes this problem by reset node managed pages to 0 after hot-adding
> a new node.
>
> 1. Move reset_managed_pages_done from reset_node_managed_pages() to reset_all_zones_managed_pages()
> 2. Make reset_node_managed_pages() non-static
> 3. Call reset_node_managed_pages() in hotadd_new_pgdat() after pgdat is initialized
>
> Signed-off-by: Tang Chen <[email protected]>
> Signed-off-by: Yasuaki Ishimatsu <[email protected]>
> ---
> include/linux/bootmem.h | 1 +
> mm/bootmem.c | 9 +++++----
> mm/memory_hotplug.c | 9 +++++++++
> mm/nobootmem.c | 8 +++++---
> 4 files changed, 20 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
> index 4e2bd4c..0995c2d 100644
> --- a/include/linux/bootmem.h
> +++ b/include/linux/bootmem.h
> @@ -46,6 +46,7 @@ extern unsigned long init_bootmem_node(pg_data_t *pgdat,
> extern unsigned long init_bootmem(unsigned long addr, unsigned long memend);
>
> extern unsigned long free_all_bootmem(void);
> +extern void reset_node_managed_pages(pg_data_t *pgdat);
> extern void reset_all_zones_managed_pages(void);
>
> extern void free_bootmem_node(pg_data_t *pgdat,
> diff --git a/mm/bootmem.c b/mm/bootmem.c
> index 8a000ce..477be69 100644
> --- a/mm/bootmem.c
> +++ b/mm/bootmem.c
> @@ -243,13 +243,10 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
>
> static int reset_managed_pages_done __initdata;
>
> -static inline void __init reset_node_managed_pages(pg_data_t *pgdat)
> +void reset_node_managed_pages(pg_data_t *pgdat)
> {
> struct zone *z;
>
> - if (reset_managed_pages_done)
> - return;
> -
> for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
> z->managed_pages = 0;
> }
> @@ -258,8 +255,12 @@ void __init reset_all_zones_managed_pages(void)
> {
> struct pglist_data *pgdat;
>
> + if (reset_managed_pages_done)
> + return;
> +
> for_each_online_pgdat(pgdat)
> reset_node_managed_pages(pgdat);
> +
> reset_managed_pages_done = 1;
> }
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 29d8693..3ab01b2 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -31,6 +31,7 @@
> #include <linux/stop_machine.h>
> #include <linux/hugetlb.h>
> #include <linux/memblock.h>
> +#include <linux/bootmem.h>
>
> #include <asm/tlbflush.h>
>
> @@ -1096,6 +1097,14 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
> build_all_zonelists(pgdat, NULL);
> mutex_unlock(&zonelists_mutex);
>
> + /*
> + * zone->managed_pages is set to an approximate value in
> + * free_area_init_core(), which will cause
> + * /sys/device/system/node/nodeX/meminfo has wrong data.
> + * So reset it to 0 before any memory is onlined.
> + */
> + reset_node_managed_pages(pgdat);
> +
I aggree with you, we should reset it before online pages.
Thanks,
Xishi Qiu
> return pgdat;
> }
>
> diff --git a/mm/nobootmem.c b/mm/nobootmem.c
> index 7c7ab32..90b5046 100644
> --- a/mm/nobootmem.c
> +++ b/mm/nobootmem.c
> @@ -145,12 +145,10 @@ static unsigned long __init free_low_memory_core_early(void)
>
> static int reset_managed_pages_done __initdata;
>
> -static inline void __init reset_node_managed_pages(pg_data_t *pgdat)
> +void reset_node_managed_pages(pg_data_t *pgdat)
> {
> struct zone *z;
>
> - if (reset_managed_pages_done)
> - return;
> for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
> z->managed_pages = 0;
> }
> @@ -159,8 +157,12 @@ void __init reset_all_zones_managed_pages(void)
> {
> struct pglist_data *pgdat;
>
> + if (reset_managed_pages_done)
> + return;
> +
> for_each_online_pgdat(pgdat)
> reset_node_managed_pages(pgdat);
> +
> reset_managed_pages_done = 1;
> }
>
(2014/10/31 18:46), Tang Chen wrote:
> When we are doing memory hot-add, the following functions are called:
>
> add_memory()
> |--> hotadd_new_pgdat()
> |--> free_area_init_node()
> |--> free_area_init_core()
> |--> zone->present_pages = realsize; /* 1. zone is populated */
> |--> zone_pcp_init()
> |--> zone->pageset = &boot_pageset; /* 2. zone->pageset is set to boot_pageset */
>
> There are two problems here:
> 1. Zones could be populated before any memory is onlined.
> 2. All the zones on a newly added node have the same pageset pointing to boot_pageset.
>
> The above two problems will result in the following problem:
> When we online memory on one node, e.g node2, the following code is executed:
>
> online_pages()
> {
> ......
> if (!populated_zone(zone)) {
> need_zonelists_rebuild = 1;
> build_all_zonelists(NULL, zone);
> }
> ......
> }
>
> Because of problem 1, the zone has been populated, and the build_all_zonelists()
> will never called. zone->pageset won't be updated.
> Because of problem 2, All the zones on a newly added node have the same pageset
> pointing to boot_pageset.
> And as a result, when we online memory on node2, node3's meminfo will corrupt.
> Pages on node2 may be freed to node3.
>
> # for ((i = 2048; i < 2064; i++)); do echo online_movable > /sys/devices/system/node/node2/memory$i/state; done
> # cat /sys/devices/system/node/node2/meminfo
> Node 2 MemTotal: 33554432 kB
> Node 2 MemFree: 33549092 kB
> Node 2 MemUsed: 5340 kB
> ......
> # cat /sys/devices/system/node/node3/meminfo
> Node 3 MemTotal: 0 kB
> Node 3 MemFree: 248 kB /* corrupted */
> Node 3 MemUsed: 0 kB
> ......
>
> We have to populate some zones before onlining memory, otherwise no memory could be onlined.
> So when onlining pages, we should also check if zone->pageset is pointing to boot_pageset.
>
> Signed-off-by: Gu Zheng <[email protected]>
> Signed-off-by: Tang Chen <[email protected]>
> ---
> include/linux/mm.h | 1 +
> mm/memory_hotplug.c | 6 +++++-
> mm/page_alloc.c | 5 +++++
> 3 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 02d11ee..83e6505 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1732,6 +1732,7 @@ void warn_alloc_failed(gfp_t gfp_mask, int order, const char *fmt, ...);
>
> extern void setup_per_cpu_pageset(void);
>
> +extern bool zone_pcp_initialized(struct zone *zone);
> extern void zone_pcp_update(struct zone *zone);
> extern void zone_pcp_reset(struct zone *zone);
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 3ab01b2..bc0de0f 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1013,9 +1013,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
> * If this zone is not populated, then it is not in zonelist.
> * This means the page allocator ignores this zone.
> * So, zonelist must be updated after online.
> + *
> + * If this zone is populated, zone->pageset could be initialized
> + * to boot_pageset for the first time a node is added. If so,
> + * zone->pageset should be allocated.
> */
> mutex_lock(&zonelists_mutex);
> - if (!populated_zone(zone)) {
> + if (!populated_zone(zone) || !zone_pcp_initialized(zone)) {
> need_zonelists_rebuild = 1;
> build_all_zonelists(NULL, zone);
> }
Why does zone->present_pages of the hot-added memroy have valid value?
In my understading, the present_pages is incremented/decremented by memory
online/offline. So when hot adding memory, the zone->present_pages of the
memory should be 0.
Thanks,
Yasuaki Ishimatsu
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 736d8e1..4ff1540 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6456,6 +6456,11 @@ void __meminit zone_pcp_update(struct zone *zone)
> }
> #endif
>
> +bool zone_pcp_initialized(struct zone *zone)
> +{
> + return (zone->pageset != &boot_pageset);
> +}
> +
> void zone_pcp_reset(struct zone *zone)
> {
> unsigned long flags;
>
On 11/04/2014 04:10 PM, Yasuaki Ishimatsu wrote:
> (2014/10/31 18:46), Tang Chen wrote:
>> When we are doing memory hot-add, the following functions are called:
>>
>> add_memory()
>> |--> hotadd_new_pgdat()
>> |--> free_area_init_node()
>> |--> free_area_init_core()
>> |--> zone->present_pages = realsize; /* 1. zone is populated */
>> |--> zone_pcp_init()
>> |--> zone->pageset = &boot_pageset; /* 2. zone->pageset is set to boot_pageset */
>>
>> There are two problems here:
>> 1. Zones could be populated before any memory is onlined.
>> 2. All the zones on a newly added node have the same pageset pointing to boot_pageset.
>>
>> The above two problems will result in the following problem:
>> When we online memory on one node, e.g node2, the following code is executed:
>>
>> online_pages()
>> {
>> ......
>> if (!populated_zone(zone)) {
>> need_zonelists_rebuild = 1;
>> build_all_zonelists(NULL, zone);
>> }
>> ......
>> }
>>
>> Because of problem 1, the zone has been populated, and the build_all_zonelists()
>> will never called. zone->pageset won't be updated.
>> Because of problem 2, All the zones on a newly added node have the same pageset
>> pointing to boot_pageset.
>> And as a result, when we online memory on node2, node3's meminfo will corrupt.
>> Pages on node2 may be freed to node3.
>>
>> # for ((i = 2048; i < 2064; i++)); do echo online_movable > /sys/devices/system/node/node2/memory$i/state; done
>> # cat /sys/devices/system/node/node2/meminfo
>> Node 2 MemTotal: 33554432 kB
>> Node 2 MemFree: 33549092 kB
>> Node 2 MemUsed: 5340 kB
>> ......
>> # cat /sys/devices/system/node/node3/meminfo
>> Node 3 MemTotal: 0 kB
>> Node 3 MemFree: 248 kB /* corrupted */
>> Node 3 MemUsed: 0 kB
>> ......
>>
>> We have to populate some zones before onlining memory, otherwise no memory could be onlined.
>> So when onlining pages, we should also check if zone->pageset is pointing to boot_pageset.
>>
>> Signed-off-by: Gu Zheng <[email protected]>
>> Signed-off-by: Tang Chen <[email protected]>
>> ---
>> include/linux/mm.h | 1 +
>> mm/memory_hotplug.c | 6 +++++-
>> mm/page_alloc.c | 5 +++++
>> 3 files changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 02d11ee..83e6505 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -1732,6 +1732,7 @@ void warn_alloc_failed(gfp_t gfp_mask, int order, const char *fmt, ...);
>>
>> extern void setup_per_cpu_pageset(void);
>>
>> +extern bool zone_pcp_initialized(struct zone *zone);
>> extern void zone_pcp_update(struct zone *zone);
>> extern void zone_pcp_reset(struct zone *zone);
>>
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 3ab01b2..bc0de0f 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1013,9 +1013,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
>> * If this zone is not populated, then it is not in zonelist.
>> * This means the page allocator ignores this zone.
>> * So, zonelist must be updated after online.
>> + *
>> + * If this zone is populated, zone->pageset could be initialized
>> + * to boot_pageset for the first time a node is added. If so,
>> + * zone->pageset should be allocated.
>> */
>> mutex_lock(&zonelists_mutex);
>> - if (!populated_zone(zone)) {
>> + if (!populated_zone(zone) || !zone_pcp_initialized(zone)) {
>> need_zonelists_rebuild = 1;
>> build_all_zonelists(NULL, zone);
>> }
> Why does zone->present_pages of the hot-added memroy have valid value?
> In my understading, the present_pages is incremented/decremented by memory
> online/offline. So when hot adding memory, the zone->present_pages of the
> memory should be 0.
Before zone->managed_pages was introduced, zone->present_pages had been
abused.
It had two meaning:
1. pages existing in the zone
2. pages managed by buddy system in the zone
So, zone->managed_pages was introduced. Now, it looks like:
1. zone->present_pages is the pages existing in the zone
2. zone->managed_pages is the pages managed by buddy system
So when hot adding memory, the zone->present_pages should not be 0.
zone->managed_pages should be 0. And here, since zone->managed_pages
is updated in online_pages_range() callback, I think we should remove
zone->present_pages and node_present_pages updates from online_pages().
Furthermore, since we can online pages or online_movable pages,
zones in a node could be changed. So we should update zone->present_pages
when pfn is moved left or right.
Thanks.
>
> Thanks,
> Yasuaki Ishimatsu
>
>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 736d8e1..4ff1540 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -6456,6 +6456,11 @@ void __meminit zone_pcp_update(struct zone *zone)
>> }
>> #endif
>>
>> +bool zone_pcp_initialized(struct zone *zone)
>> +{
>> + return (zone->pageset != &boot_pageset);
>> +}
>> +
>> void zone_pcp_reset(struct zone *zone)
>> {
>> unsigned long flags;
>>
>
> .
>
(2014/10/31 18:46), Tang Chen wrote:
> When we are doing memory hot-add, the following functions are called:
>
> add_memory()
> |--> hotadd_new_pgdat()
> |--> free_area_init_node()
> |--> free_area_init_core()
> |--> zone->present_pages = realsize; /* 1. zone is populated */
> |--> zone_pcp_init()
> |--> zone->pageset = &boot_pageset; /* 2. zone->pageset is set to boot_pageset */
>
> There are two problems here:
> 1. Zones could be populated before any memory is onlined.
> 2. All the zones on a newly added node have the same pageset pointing to boot_pageset.
>
> The above two problems will result in the following problem:
> When we online memory on one node, e.g node2, the following code is executed:
>
> online_pages()
> {
> ......
> if (!populated_zone(zone)) {
> need_zonelists_rebuild = 1;
> build_all_zonelists(NULL, zone);
> }
> ......
> }
>
> Because of problem 1, the zone has been populated, and the build_all_zonelists()
> will never called. zone->pageset won't be updated.
> Because of problem 2, All the zones on a newly added node have the same pageset
> pointing to boot_pageset.
> And as a result, when we online memory on node2, node3's meminfo will corrupt.
> Pages on node2 may be freed to node3.
>
> # for ((i = 2048; i < 2064; i++)); do echo online_movable > /sys/devices/system/node/node2/memory$i/state; done
> # cat /sys/devices/system/node/node2/meminfo
> Node 2 MemTotal: 33554432 kB
> Node 2 MemFree: 33549092 kB
> Node 2 MemUsed: 5340 kB
> ......
> # cat /sys/devices/system/node/node3/meminfo
> Node 3 MemTotal: 0 kB
> Node 3 MemFree: 248 kB /* corrupted */
> Node 3 MemUsed: 0 kB
> ......
>
> We have to populate some zones before onlining memory, otherwise no memory could be onlined.
> So when onlining pages, we should also check if zone->pageset is pointing to boot_pageset.
>
> Signed-off-by: Gu Zheng <[email protected]>
> Signed-off-by: Tang Chen <[email protected]>
> ---
> include/linux/mm.h | 1 +
> mm/memory_hotplug.c | 6 +++++-
> mm/page_alloc.c | 5 +++++
> 3 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 02d11ee..83e6505 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1732,6 +1732,7 @@ void warn_alloc_failed(gfp_t gfp_mask, int order, const char *fmt, ...);
>
> extern void setup_per_cpu_pageset(void);
>
> +extern bool zone_pcp_initialized(struct zone *zone);
> extern void zone_pcp_update(struct zone *zone);
> extern void zone_pcp_reset(struct zone *zone);
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 3ab01b2..bc0de0f 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1013,9 +1013,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
> * If this zone is not populated, then it is not in zonelist.
> * This means the page allocator ignores this zone.
> * So, zonelist must be updated after online.
> + *
> + * If this zone is populated, zone->pageset could be initialized
> + * to boot_pageset for the first time a node is added. If so,
> + * zone->pageset should be allocated.
> */
> mutex_lock(&zonelists_mutex);
> - if (!populated_zone(zone)) {
> + if (!populated_zone(zone) || !zone_pcp_initialized(zone)) {
Please don't add another strange meanings to zone's pcplist.
If you say zone->present_pages doesn't mean zone has pages in buddy list any more,
please rewrite all parts using zone->present_pages including populated_zone().
I think there are several parts calculates parameters based on present_pages.
I myself doesn't welcome having both of compliated "managed pages" and "present pages"...
How about adding
static inline int managed_zone(struct zone *zone)
{
return (!!zone->managed_pages);
}
for this bug fix ?
Other parts, using present_pages, should be considered well.
Thanks,
-Kame
Thanks,
-Kame
> need_zonelists_rebuild = 1;
> build_all_zonelists(NULL, zone);
> }
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 736d8e1..4ff1540 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6456,6 +6456,11 @@ void __meminit zone_pcp_update(struct zone *zone)
> }
> #endif
>
> +bool zone_pcp_initialized(struct zone *zone)
> +{
> + return (zone->pageset != &boot_pageset);
> +}
> +
> void zone_pcp_reset(struct zone *zone)
> {
> unsigned long flags;
>
On 11/05/2014 09:01 AM, Kamezawa Hiroyuki wrote:
> ......
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 3ab01b2..bc0de0f 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1013,9 +1013,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
> * If this zone is not populated, then it is not in zonelist.
> * This means the page allocator ignores this zone.
> * So, zonelist must be updated after online.
> + *
> + * If this zone is populated, zone->pageset could be initialized
> + * to boot_pageset for the first time a node is added. If so,
> + * zone->pageset should be allocated.
> */
> mutex_lock(&zonelists_mutex);
> - if (!populated_zone(zone)) {
> + if (!populated_zone(zone) || !zone_pcp_initialized(zone)) {
> Please don't add another strange meanings to zone's pcplist.
>
> If you say zone->present_pages doesn't mean zone has pages in buddy list any more,
> please rewrite all parts using zone->present_pages including populated_zone().
Adding Liu Jiang...
I think zone->managed_pages was introduced by Liu Jiang in the following
patch:
>From 9feedc9d831e18ae6d0d15aa562e5e46ba53647b Mon Sep 17 00:00:00 2001
From: Jiang Liu <[email protected]>
Date: Wed, 12 Dec 2012 13:52:12 -0800
Subject: [PATCH 1/1] mm: introduce new field "managed_pages" to struct zone
Before this patch, zone->present_pages meant "amount of memory
(excluding holes)",
not the zone has pages in buddy system.
So I think zone->present_pages keeps its meaning as before. But it may
be abused
somewhere else, such as here.
> I think there are several parts calculates parameters based on present_pages.
>
> I myself doesn't welcome having both of compliated "managed pages" and "present pages"...
>
> How about adding
>
> static inline int managed_zone(struct zone *zone)
> {
> return (!!zone->managed_pages);
> }
>
> for this bug fix ?
Yes, adding this function could fix this problem.
And by the way, we have the following code in onine_pages():
zone->present_pages += onlined_pages;
pgdat_resize_lock(zone->zone_pgdat, &flags);
zone->zone_pgdat->node_present_pages += onlined_pages;
pgdat_resize_unlock(zone->zone_pgdat, &flags);
We should do this when the zone size is changed, not where it is now.
Will send patches for this soon.
Thanks.
>
> Other parts, using present_pages, should be considered well.
>
>