Subject: [PATCH] powerpc/64s/radix: Enable huge vmalloc mappings

From: Nicholas Piggin <[email-masked]>
Date: Sun, 2 May 2021 14:56:15 +1000

This reduces TLB misses by nearly 30x on a `git diff` workload on a
2-node POWER9 (59,800 -> 2,100) and reduces CPU cycles by 0.54%, due
to vfs hashes being allocated with 2MB pages.

Acked-by: Michael Ellerman <[email-masked]>
Signed-off-by: Nicholas Piggin <[email-masked]>
---
This was in the -mm tree but was dropped at the last minute after
clashing with a patch in powerpc next.

Now all prerequisites are upstream, this can be merged as is. Probably
makes sense now to go via powerpc tree.

This is rebased and retested on upstream.

 Documentation/admin-guide/kernel-parameters.txt |  2 ++
 arch/powerpc/Kconfig                            |  1 +
 arch/powerpc/include/asm/pgtable.h              |  5 +++++
 arch/powerpc/kernel/module.c                    | 16 +++++++++++++---
 4 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1c0a3cf6fcc9..1be38b25c485 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3250,6 +3250,8 @@
 
 	nohugeiomap	[KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
 
+	nohugevmalloc	[PPC] Disable kernel huge vmalloc mappings.
+
 	nosmt		[KNL,S390] Disable symmetric multithreading (SMT).
 			Equivalent to smt=1.
 
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 1e6230bea09d..c547a9d6a2dd 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -185,6 +185,7 @@ config PPC
 	select GENERIC_VDSO_TIME_NS
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_HUGE_VMAP		if PPC_BOOK3S_64 && PPC_RADIX_MMU
+	select HAVE_ARCH_HUGE_VMALLOC		if HAVE_ARCH_HUGE_VMAP
 	select HAVE_ARCH_JUMP_LABEL
 	select HAVE_ARCH_JUMP_LABEL_RELATIVE
 	select HAVE_ARCH_KASAN			if PPC32 && PPC_PAGE_SHIFT <= 14
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index c6a676714f04..1678e4b08fc3 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -39,6 +39,11 @@ struct mm_struct;
 #define __S110	PAGE_SHARED_X
 #define __S111	PAGE_SHARED_X
 
+#ifndef MODULES_VADDR
+#define MODULES_VADDR	VMALLOC_START
+#define MODULES_END	VMALLOC_END
+#endif
+
 #ifndef __ASSEMBLY__
 
 /* Keep these as a macros to avoid include dependency mess */
diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
index fab84024650c..77aefcbbd276 100644
--- a/arch/powerpc/kernel/module.c
+++ b/arch/powerpc/kernel/module.c
@@ -8,6 +8,7 @@
 #include <linux/moduleloader.h>
 #include <linux/err.h>
 #include <linux/vmalloc.h>
+#include <linux/mm.h>
 #include <linux/bug.h>
 #include <asm/module.h>
 #include <linux/uaccess.h>
@@ -88,17 +89,24 @@ int module_finalize(const Elf_Ehdr *hdr,
 	return 0;
 }
 
-#ifdef MODULES_VADDR
 static __always_inline void *
 __module_alloc(unsigned long size, unsigned long start, unsigned long end)
 {
+	/*
+	 * Don't do huge page allocations for modules yet until more testing
+	 * is done. STRICT_MODULE_RWX may require extra work to support this
+	 * too.
+	 */
 	return __vmalloc_node_range(size, 1, start, end, GFP_KERNEL,
-				    PAGE_KERNEL_EXEC, VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
+				    PAGE_KERNEL_EXEC,
+				    VM_FLUSH_RESET_PERMS | VM_NO_HUGE_VMAP,
+				    NUMA_NO_NODE,
 				    __builtin_return_address(0));
 }
 
 void *module_alloc(unsigned long size)
 {
+#ifdef CONFIG_PPC32
 	unsigned long limit = (unsigned long)_etext - SZ_32M;
 	void *ptr = NULL;
 
@@ -112,5 +120,7 @@ void *module_alloc(unsigned long size)
 		ptr = __module_alloc(size, MODULES_VADDR, MODULES_END);
 
 	return ptr;
-}
+#else
+	return __module_alloc(size, MODULES_VADDR, MODULES_END);
 #endif
+}
-- 
2.23.0