Every time a memory hotplug happens, and the memory limit crosses a 2^n
value, it may be necessary to perform HPT resizing-up, which can take
some time (over 100ms in my tests).
It usually is not an issue, but it can take some time if a lot of memory
is added to a guest with little starting memory:
Adding 256G to a 2GB guest, for example will require 8 HPT resizes.
Perform an HPT resize before memory hotplug, updating HPT to its
final size (considering a successful hotplug), taking the number of
HPT resizes to at most one per memory hotplug action.
Signed-off-by: Leonardo Bras <leobra...@gmail.com>
---
arch/powerpc/include/asm/book3s/64/hash.h | 2 ++
arch/powerpc/mm/book3s64/hash_utils.c | 20 +++++++++++++++++++
.../platforms/pseries/hotplug-memory.c | 9 +++++++++
3 files changed, 31 insertions(+)
diff --git a/arch/powerpc/include/asm/book3s/64/hash.h
b/arch/powerpc/include/asm/book3s/64/hash.h
index d959b0195ad9..fad4af8b8543 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -255,6 +255,8 @@ int hash__create_section_mapping(unsigned long start,
unsigned long end,
int nid, pgprot_t prot);
int hash__remove_section_mapping(unsigned long start, unsigned long end);
+void hash_batch_expand_prepare(unsigned long newsize);
+
#endif /* !__ASSEMBLY__ */
#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_BOOK3S_64_HASH_H */
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c
b/arch/powerpc/mm/book3s64/hash_utils.c
index 608e4ed397a9..3fa395b3fe57 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -859,6 +859,26 @@ int hash__remove_section_mapping(unsigned long start,
unsigned long end)
return rc;
}
+
+void hash_batch_expand_prepare(unsigned long newsize)
+{
+ const u64 starting_size = ppc64_pft_size;
+
+ /*
+ * Resizing-up HPT should never fail, but there are some cases system
starts with higher
+ * SHIFT than required, and we go through the funny case of resizing
HPT down while
+ * adding memory
+ */
+
+ while (resize_hpt_for_hotplug(newsize, false) == -ENOSPC) {
+ newsize *= 2;
+ pr_warn("Hash collision while resizing HPT\n");
+
+ /* Do not try to resize to the starting size, or bigger value */
+ if (htab_shift_for_mem_size(newsize) >= starting_size)
+ break;
+ }
+}
#endif /* CONFIG_MEMORY_HOTPLUG */
static void __init hash_init_partition_table(phys_addr_t hash_table,
diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c
b/arch/powerpc/platforms/pseries/hotplug-memory.c
index 8377f1f7c78e..48b2cfe4ce69 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -13,6 +13,7 @@
#include <linux/memory.h>
#include <linux/memory_hotplug.h>
#include <linux/slab.h>
+#include <linux/pgtable.h>
#include <asm/firmware.h>
#include <asm/machdep.h>
@@ -671,6 +672,10 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add)
if (lmbs_available < lmbs_to_add)
return -EINVAL;
+ if (!radix_enabled())
+ hash_batch_expand_prepare(memblock_phys_mem_size() +
+ lmbs_to_add *
drmem_lmb_size());
+
for_each_drmem_lmb(lmb) {
if (lmb->flags & DRCONF_MEM_ASSIGNED)
continue;
@@ -788,6 +793,10 @@ static int dlpar_memory_add_by_ic(u32 lmbs_to_add, u32
drc_index)
if (lmbs_available < lmbs_to_add)
return -EINVAL;
+ if (!radix_enabled())
+ hash_batch_expand_prepare(memblock_phys_mem_size() +
+ lmbs_to_add * drmem_lmb_size());
+
for_each_drmem_lmb_in_range(lmb, start_lmb, end_lmb) {
if (lmb->flags & DRCONF_MEM_ASSIGNED)
continue;
--
2.30.2
