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vmalloc: replace VM_NO_HUGE_VMAP with VM_ALLOW_HUGE_VMAP 

Huge page backed vmalloc memory could benefit performance in many cases.
However, some users of vmalloc may not be ready to handle huge pages for
various reasons: hardware constraints, potential pages split, etc.
VM_NO_HUGE_VMAP was introduced to allow vmalloc users to opt-out huge
pages.  However, it is not easy to track down all the users that require
the opt-out, as the allocation are passed different stacks and may cause
issues in different layers.

To address this issue, 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.

Also, remove vmalloc_no_huge() and add opt-in helper vmalloc_huge().

Fixes: fac54e2bfb ("x86/Kconfig: Select HAVE_ARCH_HUGE_VMALLOC with HAVE_ARCH_HUGE_VMAP")
Link: https://lore.kernel.org/netdev/14444103-d51b-0fb3-ee63-c3f182f0b546@molgen.mpg.de/"
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Song Liu <song@kernel.org>
Reviewed-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Song Liu 2022-04-15 09:44:10 -07:00 committed by Linus Torvalds
parent b7f73403a3
commit 559089e0a9
5 changed files with 16 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/Kconfig
View File

@ -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

2
arch/powerpc/kernel/module.c
View File

@ -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));
}

7
arch/s390/kvm/pv.c
View File

@ -137,12 +137,7 @@ static int kvm_s390_pv_alloc_vm(struct kvm *kvm)
/* Allocate variable storage */
vlen = ALIGN(virt * ((npages * PAGE_SIZE) / HPAGE_SIZE), PAGE_SIZE);
vlen += uv_info.guest_virt_base_stor_len;
/*
* The Create Secure Configuration Ultravisor Call does not support
* 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 = vzalloc(vlen);
if (!kvm->arch.pv.stor_var)
goto out_err;
return 0;

4
include/linux/vmalloc.h
View File

@ -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 +153,7 @@ 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);
void *vmalloc_huge(unsigned long size, gfp_t gfp_mask) __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);

17
mm/vmalloc.c
View File

@ -3095,7 +3095,7 @@ 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;
/*
@ -3262,21 +3262,24 @@ void *vmalloc(unsigned long size)
EXPORT_SYMBOL(vmalloc);
/**
* vmalloc_no_huge - allocate virtually contiguous memory using small pages
* @size: allocation size
* vmalloc_huge - allocate virtually contiguous memory, allow huge pages
* @size: allocation size
* @gfp_mask: flags for the page level allocator
*
* Allocate enough non-huge pages to cover @size from the page level
* Allocate enough pages to cover @size from the page level
* allocator and map them into contiguous kernel virtual space.
* If @size is greater than or equal to PMD_SIZE, allow using
* huge pages for the memory
*
* Return: pointer to the allocated memory or %NULL on error
*/
void *vmalloc_no_huge(unsigned long size)
void *vmalloc_huge(unsigned long size, gfp_t gfp_mask)
{
return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
GFP_KERNEL, PAGE_KERNEL, VM_NO_HUGE_VMAP,
gfp_mask, PAGE_KERNEL, VM_ALLOW_HUGE_VMAP,
NUMA_NO_NODE, __builtin_return_address(0));
}
EXPORT_SYMBOL(vmalloc_no_huge);
EXPORT_SYMBOL_GPL(vmalloc_huge);
/**
* vzalloc - allocate virtually contiguous memory with zero fill