From: David Gibson <david@gibson.dropbear.id.au>
Date: Fri, 9 Dec 2016 00:07:38 +0000 (+1100)
Subject: powerpc/pseries: Automatically resize HPT for memory hot add/remove
X-Git-Tag: MMI-PSA29.97-13-9~6064^2~62
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=438cc81a41e8;p=GitHub%2FMotorolaMobilityLLC%2Fkernel-slsi.git

powerpc/pseries: Automatically resize HPT for memory hot add/remove

We've now implemented code in the pseries platform to use the new PAPR
interface to allow resizing the hash page table (HPT) at runtime.

This patch uses that interface to automatically attempt to resize the HPT
when memory is hot added or removed.  This tries to always keep the HPT at
a reasonable size for our current memory size.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---

diff --git a/arch/powerpc/include/asm/sparsemem.h b/arch/powerpc/include/asm/sparsemem.h
index f6fc0ee813d7..737335c891e4 100644
--- a/arch/powerpc/include/asm/sparsemem.h
+++ b/arch/powerpc/include/asm/sparsemem.h
@@ -16,6 +16,7 @@
 #endif /* CONFIG_SPARSEMEM */
 
 #ifdef CONFIG_MEMORY_HOTPLUG
+extern void resize_hpt_for_hotplug(unsigned long new_mem_size);
 extern int create_section_mapping(unsigned long start, unsigned long end);
 extern int remove_section_mapping(unsigned long start, unsigned long end);
 #ifdef CONFIG_NUMA
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index a3371d4e35b6..12d679df50bd 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -749,6 +749,35 @@ static unsigned long __init htab_get_table_size(void)
 }
 
 #ifdef CONFIG_MEMORY_HOTPLUG
+void resize_hpt_for_hotplug(unsigned long new_mem_size)
+{
+	unsigned target_hpt_shift;
+
+	if (!mmu_hash_ops.resize_hpt)
+		return;
+
+	target_hpt_shift = htab_shift_for_mem_size(new_mem_size);
+
+	/*
+	 * To avoid lots of HPT resizes if memory size is fluctuating
+	 * across a boundary, we deliberately have some hysterisis
+	 * here: we immediately increase the HPT size if the target
+	 * shift exceeds the current shift, but we won't attempt to
+	 * reduce unless the target shift is at least 2 below the
+	 * current shift
+	 */
+	if ((target_hpt_shift > ppc64_pft_size)
+	    || (target_hpt_shift < (ppc64_pft_size - 1))) {
+		int rc;
+
+		rc = mmu_hash_ops.resize_hpt(target_hpt_shift);
+		if (rc)
+			printk(KERN_WARNING
+			       "Unable to resize hash page table to target order %d: %d\n",
+			       target_hpt_shift, rc);
+	}
+}
+
 int hash__create_section_mapping(unsigned long start, unsigned long end)
 {
 	int rc = htab_bolt_mapping(start, end, __pa(start),
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 5f844337de21..9ee536ec0739 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -134,6 +134,8 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
 	unsigned long nr_pages = size >> PAGE_SHIFT;
 	int rc;
 
+	resize_hpt_for_hotplug(memblock_phys_mem_size());
+
 	pgdata = NODE_DATA(nid);
 
 	start = (unsigned long)__va(start);
@@ -174,6 +176,8 @@ int arch_remove_memory(u64 start, u64 size)
 	 */
 	vm_unmap_aliases();
 
+	resize_hpt_for_hotplug(memblock_phys_mem_size());
+
 	return ret;
 }
 #endif