diff mbox series

[bpf,1/2] vmalloc: replace VM_NO_HUGE_VMAP with VM_ALLOW_HUGE_VMAP

Message ID 20220408223443.3303509-2-song@kernel.org (mailing list archive)
State New
Headers show
Series vmalloc: bpf: introduce VM_ALLOW_HUGE_VMAP | expand

Commit Message

Song Liu April 8, 2022, 10:34 p.m. UTC 
Huge page backed vmalloc memory could benefit performance in many cases.
Since some users of vmalloc may not be ready to handle huge pages,
VM_NO_HUGE_VMAP was introduced to allow vmalloc users to opt-out huge
pages. However, it is not easy to add VM_NO_HUGE_VMAP to all the users
that may try to allocate >= PMD_SIZE pages, but are not ready to handle
huge pages properly.

Replace VM_NO_HUGE_VMAP with an opt-in flag, VM_ALLOW_HUGE_VMAP, so that
users that benefit from huge pages could ask specificially.

Signed-off-by: Song Liu <song@kernel.org>
---
 arch/Kconfig                 |  6 ++----
 arch/powerpc/kernel/module.c |  2 +-
 arch/s390/kvm/pv.c           |  2 +-
 include/linux/vmalloc.h      |  3 +--
 mm/vmalloc.c                 | 19 +------------------
 5 files changed, 6 insertions(+), 26 deletions(-)

Comments

Christoph Hellwig April 9, 2022, 5:28 a.m. UTC | #1 
On Fri, Apr 08, 2022 at 03:34:42PM -0700, Song Liu wrote:
> Huge page backed vmalloc memory could benefit performance in many cases.
> Since some users of vmalloc may not be ready to handle huge pages,
> VM_NO_HUGE_VMAP was introduced to allow vmalloc users to opt-out huge
> pages. However, it is not easy to add VM_NO_HUGE_VMAP to all the users
> that may try to allocate >= PMD_SIZE pages, but are not ready to handle
> huge pages properly.
> 
> Replace VM_NO_HUGE_VMAP with an opt-in flag, VM_ALLOW_HUGE_VMAP, so that
> users that benefit from huge pages could ask specificially.

Given that the huge page backing was added explicitly for some big boot
time allocated hashed,those should probably have the VM_ALLOW_HUGE_VMAP
added from the start (maybe not in this patch, but certainly in this
series).  We'll probably also need a vmalloc_huge interface for those.
Song Liu April 10, 2022, 1:25 a.m. UTC | #2 
> On Apr 8, 2022, at 10:28 PM, Christoph Hellwig <hch@infradead.org> wrote:
> 
> On Fri, Apr 08, 2022 at 03:34:42PM -0700, Song Liu wrote:
>> Huge page backed vmalloc memory could benefit performance in many cases.
>> Since some users of vmalloc may not be ready to handle huge pages,
>> VM_NO_HUGE_VMAP was introduced to allow vmalloc users to opt-out huge
>> pages. However, it is not easy to add VM_NO_HUGE_VMAP to all the users
>> that may try to allocate >= PMD_SIZE pages, but are not ready to handle
>> huge pages properly.
>> 
>> Replace VM_NO_HUGE_VMAP with an opt-in flag, VM_ALLOW_HUGE_VMAP, so that
>> users that benefit from huge pages could ask specificially.
> 
> Given that the huge page backing was added explicitly for some big boot
> time allocated hashed,those should probably have the VM_ALLOW_HUGE_VMAP
> added from the start (maybe not in this patch, but certainly in this
> series).  We'll probably also need a vmalloc_huge interface for those.

Will add it in v2. 

Thanks,
Song
diff mbox series

Patch

diff --git a/arch/Kconfig b/arch/Kconfig
index 29b0167c088b..31c4fdc4a4ba 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -854,10 +854,8 @@  config HAVE_ARCH_HUGE_VMAP
 
 #
 #  Archs that select this would be capable of PMD-sized vmaps (i.e.,
-#  arch_vmap_pmd_supported() returns true), and they must make no assumptions
-#  that vmalloc memory is mapped with PAGE_SIZE ptes. The VM_NO_HUGE_VMAP flag
-#  can be used to prohibit arch-specific allocations from using hugepages to
-#  help with this (e.g., modules may require it).
+#  arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag
+#  must be used to enable allocations to use hugepages.
 #
 config HAVE_ARCH_HUGE_VMALLOC
 	depends on HAVE_ARCH_HUGE_VMAP
diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
index 40a583e9d3c7..97a76a8619fb 100644
--- a/arch/powerpc/kernel/module.c
+++ b/arch/powerpc/kernel/module.c
@@ -101,7 +101,7 @@  __module_alloc(unsigned long size, unsigned long start, unsigned long end, bool
 	 * too.
 	 */
 	return __vmalloc_node_range(size, 1, start, end, gfp, prot,
-				    VM_FLUSH_RESET_PERMS | VM_NO_HUGE_VMAP,
+				    VM_FLUSH_RESET_PERMS,
 				    NUMA_NO_NODE, __builtin_return_address(0));
 }
 
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 7f7c0d6af2ce..8afede243903 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -142,7 +142,7 @@  static int kvm_s390_pv_alloc_vm(struct kvm *kvm)
 	 * using large pages for the virtual memory area.
 	 * This is a hardware limitation.
 	 */
-	kvm->arch.pv.stor_var = vmalloc_no_huge(vlen);
+	kvm->arch.pv.stor_var = vmalloc(vlen);
 	if (!kvm->arch.pv.stor_var)
 		goto out_err;
 	return 0;
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 3b1df7da402d..5fe76e6d1cc2 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -26,7 +26,7 @@  struct notifier_block;		/* in notifier.h */
 #define VM_KASAN		0x00000080      /* has allocated kasan shadow memory */
 #define VM_FLUSH_RESET_PERMS	0x00000100	/* reset direct map and flush TLB on unmap, can't be freed in atomic context */
 #define VM_MAP_PUT_PAGES	0x00000200	/* put pages and free array in vfree */
-#define VM_NO_HUGE_VMAP		0x00000400	/* force PAGE_SIZE pte mapping */
+#define VM_ALLOW_HUGE_VMAP	0x00000400      /* Allow for huge pages on archs with HAVE_ARCH_HUGE_VMALLOC */
 
 #if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) && \
 	!defined(CONFIG_KASAN_VMALLOC)
@@ -153,7 +153,6 @@  extern void *__vmalloc_node_range(unsigned long size, unsigned long align,
 			const void *caller) __alloc_size(1);
 void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
 		int node, const void *caller) __alloc_size(1);
-void *vmalloc_no_huge(unsigned long size) __alloc_size(1);
 
 extern void *__vmalloc_array(size_t n, size_t size, gfp_t flags) __alloc_size(1, 2);
 extern void *vmalloc_array(size_t n, size_t size) __alloc_size(1, 2);
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index e163372d3967..7e9b140f652d 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3106,7 +3106,7 @@  void *__vmalloc_node_range(unsigned long size, unsigned long align,
 		return NULL;
 	}
 
-	if (vmap_allow_huge && !(vm_flags & VM_NO_HUGE_VMAP)) {
+	if (vmap_allow_huge && (vm_flags & VM_ALLOW_HUGE_VMAP)) {
 		unsigned long size_per_node;
 
 		/*
@@ -3272,23 +3272,6 @@  void *vmalloc(unsigned long size)
 }
 EXPORT_SYMBOL(vmalloc);
 
-/**
- * vmalloc_no_huge - allocate virtually contiguous memory using small pages
- * @size:    allocation size
- *
- * Allocate enough non-huge pages to cover @size from the page level
- * allocator and map them into contiguous kernel virtual space.
- *
- * Return: pointer to the allocated memory or %NULL on error
- */
-void *vmalloc_no_huge(unsigned long size)
-{
-	return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
-				    GFP_KERNEL, PAGE_KERNEL, VM_NO_HUGE_VMAP,
-				    NUMA_NO_NODE, __builtin_return_address(0));
-}
-EXPORT_SYMBOL(vmalloc_no_huge);
-
 /**
  * vzalloc - allocate virtually contiguous memory with zero fill
  * @size:    allocation size