In offline_pages(), if a node becomes memoryless, we
will clear its N_MEMORY state by calling node_states_clear_node().
But we do this after rebuilding the zonelists by calling
build_all_zonelists(), which will cause this memoryless node to
still be in the fallback list of other nodes. This will incur
some runtime overhead.
To drop memoryless node from fallback lists in this case, just
call node_states_clear_node() before calling build_all_zonelists().
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Acked-by: David Hildenbrand <david@redhat.com>
---
mm/memory_hotplug.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index d4a364fdaf8f..f019f7d6272c 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -2036,12 +2036,16 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
/* reinitialise watermarks and update pcp limits */
init_per_zone_wmark_min();
+ /*
+ * Make sure to mark the node as memory-less before rebuilding the zone
+ * list. Otherwise this node would still appear in the fallback lists.
+ */
+ node_states_clear_node(node, &arg);
if (!populated_zone(zone)) {
zone_pcp_reset(zone);
build_all_zonelists(NULL);
}
- node_states_clear_node(node, &arg);
if (arg.status_change_nid >= 0) {
kcompactd_stop(node);
kswapd_stop(node);
--
2.30.2* Qi Zheng <zhengqi.arch@bytedance.com> wrote: > In offline_pages(), if a node becomes memoryless, we > will clear its N_MEMORY state by calling node_states_clear_node(). > But we do this after rebuilding the zonelists by calling > build_all_zonelists(), which will cause this memoryless node to > still be in the fallback list of other nodes. This will incur > some runtime overhead. > > To drop memoryless node from fallback lists in this case, just > call node_states_clear_node() before calling build_all_zonelists(). s/memoryless node /memoryless nodes > > Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> > Acked-by: David Hildenbrand <david@redhat.com> > --- > mm/memory_hotplug.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index d4a364fdaf8f..f019f7d6272c 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -2036,12 +2036,16 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages, > /* reinitialise watermarks and update pcp limits */ > init_per_zone_wmark_min(); > > + /* > + * Make sure to mark the node as memory-less before rebuilding the zone > + * list. Otherwise this node would still appear in the fallback lists. > + */ > + node_states_clear_node(node, &arg); Acked-by: Ingo Molnar <mingo@kernel.org> Thanks, Ingo
Hi Ingo, On 2023/10/20 16:32, Ingo Molnar wrote: > > * Qi Zheng <zhengqi.arch@bytedance.com> wrote: > >> In offline_pages(), if a node becomes memoryless, we >> will clear its N_MEMORY state by calling node_states_clear_node(). >> But we do this after rebuilding the zonelists by calling >> build_all_zonelists(), which will cause this memoryless node to >> still be in the fallback list of other nodes. This will incur >> some runtime overhead. >> >> To drop memoryless node from fallback lists in this case, just >> call node_states_clear_node() before calling build_all_zonelists(). > > s/memoryless node > /memoryless nodes Will do. > >> >> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> >> Acked-by: David Hildenbrand <david@redhat.com> >> --- >> mm/memory_hotplug.c | 6 +++++- >> 1 file changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >> index d4a364fdaf8f..f019f7d6272c 100644 >> --- a/mm/memory_hotplug.c >> +++ b/mm/memory_hotplug.c >> @@ -2036,12 +2036,16 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages, >> /* reinitialise watermarks and update pcp limits */ >> init_per_zone_wmark_min(); >> >> + /* >> + * Make sure to mark the node as memory-less before rebuilding the zone >> + * list. Otherwise this node would still appear in the fallback lists. >> + */ >> + node_states_clear_node(node, &arg); > > Acked-by: Ingo Molnar <mingo@kernel.org> Thanks. > > Thanks, > > Ingo
Qi Zheng <zhengqi.arch@bytedance.com> writes:
> In offline_pages(), if a node becomes memoryless, we
> will clear its N_MEMORY state by calling node_states_clear_node().
> But we do this after rebuilding the zonelists by calling
> build_all_zonelists(), which will cause this memoryless node to
> still be in the fallback list of other nodes.
For fallback list, do you mean pgdat->node_zonelists[]? If so, in
build_all_zonelists
__build_all_zonelists
build_zonelists
build_zonelists_in_node_order
build_zonerefs_node
populated_zone() will be checked before adding zone into zonelist.
So, IIUC, we will not try to allocate from the memory less node.
--
Best Regards,
Huang, Ying
> This will incur
> some runtime overhead.
>
> To drop memoryless node from fallback lists in this case, just
> call node_states_clear_node() before calling build_all_zonelists().
>
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
> Acked-by: David Hildenbrand <david@redhat.com>
[snip]
--
Best Regards,
Huang, Ying
Hi Ying, On 2023/10/20 15:05, Huang, Ying wrote: > Qi Zheng <zhengqi.arch@bytedance.com> writes: > >> In offline_pages(), if a node becomes memoryless, we >> will clear its N_MEMORY state by calling node_states_clear_node(). >> But we do this after rebuilding the zonelists by calling >> build_all_zonelists(), which will cause this memoryless node to >> still be in the fallback list of other nodes. > > For fallback list, do you mean pgdat->node_zonelists[]? If so, in > > build_all_zonelists > __build_all_zonelists > build_zonelists > build_zonelists_in_node_order > build_zonerefs_node > > populated_zone() will be checked before adding zone into zonelist. > > So, IIUC, we will not try to allocate from the memory less node. Normally yes, but if it is the weird topology mentioned in [1], it's possible to allocate memory from it, it is a memoryless node, but it also has memory. In addition to the above case, I think it's reasonable to remove memory less node from node_order[] in advance. In this way it will not to be traversed in build_zonelists_in_node_order(). [1]. https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ Thanks, Qi > > -- > Best Regards, > Huang, Ying > > >> This will incur >> some runtime overhead. >> >> To drop memoryless node from fallback lists in this case, just >> call node_states_clear_node() before calling build_all_zonelists(). >> >> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> >> Acked-by: David Hildenbrand <david@redhat.com> > > [snip] > > -- > Best Regards, > Huang, Ying
Qi Zheng <zhengqi.arch@bytedance.com> writes: > Hi Ying, > > On 2023/10/20 15:05, Huang, Ying wrote: >> Qi Zheng <zhengqi.arch@bytedance.com> writes: >> >>> In offline_pages(), if a node becomes memoryless, we >>> will clear its N_MEMORY state by calling node_states_clear_node(). >>> But we do this after rebuilding the zonelists by calling >>> build_all_zonelists(), which will cause this memoryless node to >>> still be in the fallback list of other nodes. >> For fallback list, do you mean pgdat->node_zonelists[]? If so, in >> build_all_zonelists >> __build_all_zonelists >> build_zonelists >> build_zonelists_in_node_order >> build_zonerefs_node >> populated_zone() will be checked before adding zone into zonelist. >> So, IIUC, we will not try to allocate from the memory less node. > > Normally yes, but if it is the weird topology mentioned in [1], it's > possible to allocate memory from it, it is a memoryless node, but it > also has memory. > > In addition to the above case, I think it's reasonable to remove > memory less node from node_order[] in advance. In this way it will > not to be traversed in build_zonelists_in_node_order(). > > [1]. https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ Got it! Thank you for information. I think that it may be good to include this in the patch description to avoid potential confusing in the future. -- Best Regards, Huang, Ying > Thanks, > Qi > > >> -- >> Best Regards, >> Huang, Ying >> >>> This will incur >>> some runtime overhead. >>> >>> To drop memoryless node from fallback lists in this case, just >>> call node_states_clear_node() before calling build_all_zonelists(). >>> >>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> >>> Acked-by: David Hildenbrand <david@redhat.com> >> [snip] >> -- >> Best Regards, >> Huang, Ying
Hi Ying, On 2023/10/23 09:18, Huang, Ying wrote: > Qi Zheng <zhengqi.arch@bytedance.com> writes: > >> Hi Ying, >> >> On 2023/10/20 15:05, Huang, Ying wrote: >>> Qi Zheng <zhengqi.arch@bytedance.com> writes: >>> >>>> In offline_pages(), if a node becomes memoryless, we >>>> will clear its N_MEMORY state by calling node_states_clear_node(). >>>> But we do this after rebuilding the zonelists by calling >>>> build_all_zonelists(), which will cause this memoryless node to >>>> still be in the fallback list of other nodes. >>> For fallback list, do you mean pgdat->node_zonelists[]? If so, in >>> build_all_zonelists >>> __build_all_zonelists >>> build_zonelists >>> build_zonelists_in_node_order >>> build_zonerefs_node >>> populated_zone() will be checked before adding zone into zonelist. >>> So, IIUC, we will not try to allocate from the memory less node. >> >> Normally yes, but if it is the weird topology mentioned in [1], it's >> possible to allocate memory from it, it is a memoryless node, but it >> also has memory. >> >> In addition to the above case, I think it's reasonable to remove >> memory less node from node_order[] in advance. In this way it will >> not to be traversed in build_zonelists_in_node_order(). >> >> [1]. https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ > > Got it! Thank you for information. I think that it may be good to > include this in the patch description to avoid potential confusing in > the future. OK, maybe the commit message can be changed to the following: ``` In offline_pages(), if a node becomes memoryless, we will clear its N_MEMORY state by calling node_states_clear_node(). But we do this after rebuilding the zonelists by calling build_all_zonelists(), which will cause this memoryless node to still be in the fallback nodes (node_order[]) of other nodes. To drop memoryless nodes from fallback nodes in this case, just call node_states_clear_node() before calling build_all_zonelists(). In this way, we will not try to allocate pages from memoryless node0, then the panic mentioned in [1] will also be fixed. Even though this problem has been solved by dropping the NODE_MIN_SIZE constrain in x86 [2], it would be better to fix it in the core MM as well. [1]. https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ [2]. https://lore.kernel.org/all/20231017062215.171670-1-rppt@kernel.org/ ``` Thanks, Qi > > -- > Best Regards, > Huang, Ying > >> Thanks, >> Qi >> >> >>> -- >>> Best Regards, >>> Huang, Ying >>> >>>> This will incur >>>> some runtime overhead. >>>> >>>> To drop memoryless node from fallback lists in this case, just >>>> call node_states_clear_node() before calling build_all_zonelists(). >>>> >>>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> >>>> Acked-by: David Hildenbrand <david@redhat.com> >>> [snip] >>> -- >>> Best Regards, >>> Huang, Ying
Qi Zheng <zhengqi.arch@bytedance.com> writes: > Hi Ying, > > On 2023/10/23 09:18, Huang, Ying wrote: >> Qi Zheng <zhengqi.arch@bytedance.com> writes: >> >>> Hi Ying, >>> >>> On 2023/10/20 15:05, Huang, Ying wrote: >>>> Qi Zheng <zhengqi.arch@bytedance.com> writes: >>>> >>>>> In offline_pages(), if a node becomes memoryless, we >>>>> will clear its N_MEMORY state by calling node_states_clear_node(). >>>>> But we do this after rebuilding the zonelists by calling >>>>> build_all_zonelists(), which will cause this memoryless node to >>>>> still be in the fallback list of other nodes. >>>> For fallback list, do you mean pgdat->node_zonelists[]? If so, in >>>> build_all_zonelists >>>> __build_all_zonelists >>>> build_zonelists >>>> build_zonelists_in_node_order >>>> build_zonerefs_node >>>> populated_zone() will be checked before adding zone into zonelist. >>>> So, IIUC, we will not try to allocate from the memory less node. >>> >>> Normally yes, but if it is the weird topology mentioned in [1], it's >>> possible to allocate memory from it, it is a memoryless node, but it >>> also has memory. >>> >>> In addition to the above case, I think it's reasonable to remove >>> memory less node from node_order[] in advance. In this way it will >>> not to be traversed in build_zonelists_in_node_order(). >>> >>> [1]. https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ >> Got it! Thank you for information. I think that it may be good to >> include this in the patch description to avoid potential confusing in >> the future. > > OK, maybe the commit message can be changed to the following: > > ``` > In offline_pages(), if a node becomes memoryless, we > will clear its N_MEMORY state by calling node_states_clear_node(). > But we do this after rebuilding the zonelists by calling > build_all_zonelists(), which will cause this memoryless node to > still be in the fallback nodes (node_order[]) of other nodes. > > To drop memoryless nodes from fallback nodes in this case, just > call node_states_clear_node() before calling build_all_zonelists(). > > In this way, we will not try to allocate pages from memoryless > node0, then the panic mentioned in [1] will also be fixed. Even though > this problem has been solved by dropping the NODE_MIN_SIZE constrain > in x86 [2], it would be better to fix it in the core MM as well. > > [1]. https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ > [2]. https://lore.kernel.org/all/20231017062215.171670-1-rppt@kernel.org/ > > ``` This is helpful. Thanks! -- Best Regards, Huang, Ying > Thanks, > Qi > >> -- >> Best Regards, >> Huang, Ying >> >>> Thanks, >>> Qi >>> >>> >>>> -- >>>> Best Regards, >>>> Huang, Ying >>>> >>>>> This will incur >>>>> some runtime overhead. >>>>> >>>>> To drop memoryless node from fallback lists in this case, just >>>>> call node_states_clear_node() before calling build_all_zonelists(). >>>>> >>>>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> >>>>> Acked-by: David Hildenbrand <david@redhat.com> >>>> [snip] >>>> -- >>>> Best Regards, >>>> Huang, Ying
On 2023/10/23 11:10, Huang, Ying wrote: > Qi Zheng <zhengqi.arch@bytedance.com> writes: > >> Hi Ying, >> >> On 2023/10/23 09:18, Huang, Ying wrote: >>> Qi Zheng <zhengqi.arch@bytedance.com> writes: >>> >>>> Hi Ying, >>>> >>>> On 2023/10/20 15:05, Huang, Ying wrote: >>>>> Qi Zheng <zhengqi.arch@bytedance.com> writes: >>>>> >>>>>> In offline_pages(), if a node becomes memoryless, we >>>>>> will clear its N_MEMORY state by calling node_states_clear_node(). >>>>>> But we do this after rebuilding the zonelists by calling >>>>>> build_all_zonelists(), which will cause this memoryless node to >>>>>> still be in the fallback list of other nodes. >>>>> For fallback list, do you mean pgdat->node_zonelists[]? If so, in >>>>> build_all_zonelists >>>>> __build_all_zonelists >>>>> build_zonelists >>>>> build_zonelists_in_node_order >>>>> build_zonerefs_node >>>>> populated_zone() will be checked before adding zone into zonelist. >>>>> So, IIUC, we will not try to allocate from the memory less node. >>>> >>>> Normally yes, but if it is the weird topology mentioned in [1], it's >>>> possible to allocate memory from it, it is a memoryless node, but it >>>> also has memory. >>>> >>>> In addition to the above case, I think it's reasonable to remove >>>> memory less node from node_order[] in advance. In this way it will >>>> not to be traversed in build_zonelists_in_node_order(). >>>> >>>> [1]. https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ >>> Got it! Thank you for information. I think that it may be good to >>> include this in the patch description to avoid potential confusing in >>> the future. >> >> OK, maybe the commit message can be changed to the following: >> >> ``` >> In offline_pages(), if a node becomes memoryless, we >> will clear its N_MEMORY state by calling node_states_clear_node(). >> But we do this after rebuilding the zonelists by calling >> build_all_zonelists(), which will cause this memoryless node to >> still be in the fallback nodes (node_order[]) of other nodes. >> >> To drop memoryless nodes from fallback nodes in this case, just >> call node_states_clear_node() before calling build_all_zonelists(). >> >> In this way, we will not try to allocate pages from memoryless >> node0, then the panic mentioned in [1] will also be fixed. Even though >> this problem has been solved by dropping the NODE_MIN_SIZE constrain >> in x86 [2], it would be better to fix it in the core MM as well. >> >> [1]. https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ >> [2]. https://lore.kernel.org/all/20231017062215.171670-1-rppt@kernel.org/ >> >> ``` Hi Andrew, can you help modify the commit message to this? :) Thanks, Qi > > This is helpful. Thanks! > > -- > Best Regards, > Huang, Ying > >> Thanks, >> Qi >> >>> -- >>> Best Regards, >>> Huang, Ying >>> >>>> Thanks, >>>> Qi >>>> >>>> >>>>> -- >>>>> Best Regards, >>>>> Huang, Ying >>>>> >>>>>> This will incur >>>>>> some runtime overhead. >>>>>> >>>>>> To drop memoryless node from fallback lists in this case, just >>>>>> call node_states_clear_node() before calling build_all_zonelists(). >>>>>> >>>>>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> >>>>>> Acked-by: David Hildenbrand <david@redhat.com> >>>>> [snip] >>>>> -- >>>>> Best Regards, >>>>> Huang, Ying
© 2016 - 2025 Red Hat, Inc.