Re: [Patch V3 9/9] mm, x86: Enable memoryless node support to better support CPU/memory hotplug
From: Tang Chen
Date: Tue Aug 18 2015 - 02:12:45 EST
Hi Liu,
On 08/17/2015 11:19 AM, Jiang Liu wrote:
......
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b3a1a5d77d92..5d7ad70ace0d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2069,6 +2069,9 @@ config USE_PERCPU_NUMA_NODE_ID
def_bool y
depends on NUMA
+config HAVE_MEMORYLESS_NODES
+ def_bool NUMA
+
config ARCH_ENABLE_SPLIT_PMD_PTLOCK
def_bool y
depends on X86_64 || X86_PAE
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 07930e1d2fe9..3403f1f0f28d 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -711,6 +711,7 @@ static void acpi_map_cpu2node(acpi_handle handle, int cpu, int physid)
}
set_apicid_to_node(physid, nid);
numa_set_node(cpu, nid);
+ set_cpu_numa_mem(cpu, local_memory_node(nid));
}
#endif
}
@@ -743,9 +744,10 @@ int acpi_unmap_cpu(int cpu)
{
#ifdef CONFIG_ACPI_NUMA
set_apicid_to_node(per_cpu(x86_cpu_to_apicid, cpu), NUMA_NO_NODE);
+ set_cpu_numa_mem(cpu, NUMA_NO_NODE);
#endif
- per_cpu(x86_cpu_to_apicid, cpu) = -1;
+ per_cpu(x86_cpu_to_apicid, cpu) = BAD_APICID;
set_cpu_present(cpu, false);
num_processors--;
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index b1f3ed9c7a9e..aeec91ac6fd4 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -162,6 +162,8 @@ static void smp_callin(void)
*/
phys_id = read_apic_id();
+ set_numa_mem(local_memory_node(cpu_to_node(cpuid)));
+
/*
* the boot CPU has finished the init stage and is spinning
* on callin_map until we finish. We are free to set up this
diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index 08860bdf5744..f2a4e23bd14d 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -22,6 +22,7 @@
int __initdata numa_off;
nodemask_t numa_nodes_parsed __initdata;
+static nodemask_t numa_nodes_empty __initdata;
struct pglist_data *node_data[MAX_NUMNODES] __read_mostly;
EXPORT_SYMBOL(node_data);
@@ -560,17 +561,16 @@ static int __init numa_register_memblks(struct numa_meminfo *mi)
end = max(mi->blk[i].end, end);
}
- if (start >= end)
- continue;
-
/*
* Don't confuse VM with a node that doesn't have the
* minimum amount of memory:
*/
- if (end && (end - start) < NODE_MIN_SIZE)
- continue;
-
- alloc_node_data(nid);
+ if (start < end && (end - start) >= NODE_MIN_SIZE) {
+ alloc_node_data(nid);
+ } else if (IS_ENABLED(CONFIG_HAVE_MEMORYLESS_NODES)) {
+ alloc_node_data(nid);
+ node_set(nid, numa_nodes_empty);
Seeing from here, I think numa_nodes_empty represents all memory-less nodes.
So, since we still have cpu-less nodes out there, shall we rename it to
numa_nodes_memoryless or something similar ?
And BTW, does x86 support cpu-less node after these patches ?
Since I don't have any memory-less or cpu-less node on my box, I cannot
tell it clearly.
A node is brought online when is has memory in original kernel. So I
think it is supported.
+ }
}
/* Dump memblock with node info and return. */
@@ -587,14 +587,18 @@ static int __init numa_register_memblks(struct numa_meminfo *mi)
*/
static void __init numa_init_array(void)
{
- int rr, i;
+ int i, rr = MAX_NUMNODES;
- rr = first_node(node_online_map);
for (i = 0; i < nr_cpu_ids; i++) {
+ /* Search for an onlined node with memory */
+ do {
+ if (rr != MAX_NUMNODES)
+ rr = next_node(rr, node_online_map);
+ if (rr == MAX_NUMNODES)
+ rr = first_node(node_online_map);
+ } while (node_isset(rr, numa_nodes_empty));
+
numa_set_node(i, rr);
- rr = next_node(rr, node_online_map);
- if (rr == MAX_NUMNODES)
- rr = first_node(node_online_map);
}
}
@@ -696,9 +700,12 @@ static __init int find_near_online_node(int node)
{
int n, val;
int min_val = INT_MAX;
- int best_node = -1;
+ int best_node = NUMA_NO_NODE;
for_each_online_node(n) {
+ if (node_isset(n, numa_nodes_empty))
+ continue;
+
val = node_distance(node, n);
if (val < min_val) {
@@ -739,6 +746,22 @@ void __init init_cpu_to_node(void)
if (!node_online(node))
node = find_near_online_node(node);
numa_set_node(cpu, node);
So, CPUs are still mapped to online near node, right ?
I was expecting CPUs on a memory-less node are mapped to the node they
belong to. If so, the current memory allocator may fail because they assume
each online node has memory. I was trying to do this in my patch.
https://lkml.org/lkml/2015/7/7/205
Of course, my patch is not to support memory-less node, just run into
this problem.
+ if (node_spanned_pages(node))
+ set_cpu_numa_mem(cpu, node);
+ if (IS_ENABLED(CONFIG_HAVE_MEMORYLESS_NODES))
+ node_clear(node, numa_nodes_empty);
And since we are supporting memory-less node, it's better to provide a
for_each_memoryless_node() wrapper.
+ }
+
+ /* Destroy empty nodes */
+ if (IS_ENABLED(CONFIG_HAVE_MEMORYLESS_NODES)) {
+ int nid;
+ const size_t nd_size = roundup(sizeof(pg_data_t), PAGE_SIZE);
+
+ for_each_node_mask(nid, numa_nodes_empty) {
+ node_set_offline(nid);
+ memblock_free(__pa(node_data[nid]), nd_size);
+ node_data[nid] = NULL;
So, memory-less nodes are set offline finally. It's a little different
from what I thought.
I was expecting that both memory-less and cpu-less nodes could also be
online after
this patch, which would be very helpful to me.
But actually, they are just exist temporarily, used to set _numa_mem_ so
that cpu_to_mem()
is able to work, right ?
Thanks.
+ }
}
}
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