[PATCH v6 11/12] mm/vmalloc: Hugepage vmalloc mappings

Nicholas Piggin
2020-08-21T15:13:34Z

Support huge page vmalloc mappings. Config option HAVE_ARCH_HUGE_VMALLOC
enables support on architectures that define HAVE_ARCH_HUGE_VMAP and
supports PMD sized vmap mappings.

vmalloc will attempt to allocate PMD-sized pages if allocating PMD size or
larger, and fall back to small pages if that was unsuccessful.

Allocations that do not use PAGE_KERNEL prot are not permitted to use huge
pages, because not all callers expect this (e.g., module allocations vs
strict module rwx).

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%.

This can result in more internal fragmentation and memory overhead for a
given allocation, an option nohugevmalloc is added to disable at boot.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/Kconfig | 4 +
include/linux/vmalloc.h | 1 +
mm/page_alloc.c | 5 +-
mm/vmalloc.c | 180 ++++++++++++++++++++++++++++++----------
4 files changed, 145 insertions(+), 45 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index af14a567b493..b2b89d629317 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -616,6 +616,10 @@ config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
config HAVE_ARCH_HUGE_VMAP
bool

+config HAVE_ARCH_HUGE_VMALLOC
+ depends on HAVE_ARCH_HUGE_VMAP
+ bool
+
config ARCH_WANT_HUGE_PMD_SHARE
bool

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 15adb9a14fb6..a7449064fe35 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -58,6 +58,7 @@ struct vm_struct {
unsigned long size;
unsigned long flags;
struct page **pages;
+ unsigned int page_order;
unsigned int nr_pages;
phys_addr_t phys_addr;
const void *caller;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0e2bab486fea..b6427cc7b838 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -69,6 +69,7 @@
#include <linux/nmi.h>
#include <linux/psi.h>
#include <linux/padata.h>
+#include <linux/vmalloc.h>

#include <asm/sections.h>
#include <asm/tlbflush.h>
@@ -8102,6 +8103,7 @@ void *__init alloc_large_system_hash(const char *tablename,
void *table = NULL;
gfp_t gfp_flags;
bool virt;
+ bool huge;

/* allow the kernel cmdline to have a say */
if (!numentries) {
@@ -8169,6 +8171,7 @@ void *__init alloc_large_system_hash(const char *tablename,
} else if (get_order(size) >= MAX_ORDER || hashdist) {
table = __vmalloc(size, gfp_flags);
virt = true;
+ huge = (find_vm_area(table)->page_order > 0);
} else {
/*
* If bucketsize is not a power-of-two, we may free
@@ -8185,7 +8188,7 @@ void *__init alloc_large_system_hash(const char *tablename,

pr_info("%s hash table entries: %ld (order: %d, %lu bytes, %s)\n",
tablename, 1UL << log2qty, ilog2(size) - PAGE_SHIFT, size,
- virt ? "vmalloc" : "linear");
+ virt ? (huge ? "vmalloc hugepage" : "vmalloc") : "linear");

if (_hash_shift)
*_hash_shift = log2qty;
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 1d6cad16bda3..8db53c2d7f72 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -44,6 +44,19 @@
#include "internal.h"
#include "pgalloc-track.h"

+#ifdef CONFIG_HAVE_ARCH_HUGE_VMALLOC
+static bool __ro_after_init vmap_allow_huge = true;
+
+static int __init set_nohugevmalloc(char *str)
+{
+ vmap_allow_huge = false;
+ return 0;
+}
+early_param("nohugevmalloc", set_nohugevmalloc);
+#else /* CONFIG_HAVE_ARCH_HUGE_VMALLOC */
+static const bool vmap_allow_huge = false;
+#endif /* CONFIG_HAVE_ARCH_HUGE_VMALLOC */
+
bool is_vmalloc_addr(const void *x)
{
unsigned long addr = (unsigned long)x;
@@ -477,31 +490,12 @@ static int vmap_pages_p4d_range(pgd_t *pgd, unsigned long addr,
return 0;
}

-/**
- * map_kernel_range_noflush - map kernel VM area with the specified pages
- * @addr: start of the VM area to map
- * @size: size of the VM area to map
- * @prot: page protection flags to use
- * @pages: pages to map
- *
- * Map PFN_UP(@size) pages at @addr. The VM area @addr and @size specify should
- * have been allocated using get_vm_area() and its friends.
- *
- * NOTE:
- * This function does NOT do any cache flushing. The caller is responsible for
- * calling flush_cache_vmap() on to-be-mapped areas before calling this
- * function.
- *
- * RETURNS:
- * 0 on success, -errno on failure.
- */
-int map_kernel_range_noflush(unsigned long addr, unsigned long size,
- pgprot_t prot, struct page **pages)
+static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end,
+ pgprot_t prot, struct page **pages)
{
unsigned long start = addr;
- unsigned long end = addr + size;
- unsigned long next;
pgd_t *pgd;
+ unsigned long next;
int err = 0;
int nr = 0;
pgtbl_mod_mask mask = 0;
@@ -523,6 +517,65 @@ int map_kernel_range_noflush(unsigned long addr, unsigned long size,
return 0;
}

+static int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
+ pgprot_t prot, struct page **pages, unsigned int page_shift)
+{
+ unsigned int i, nr = (end - addr) >> PAGE_SHIFT;
+
+ WARN_ON(page_shift < PAGE_SHIFT);
+
+ if (page_shift == PAGE_SHIFT)
+ return vmap_small_pages_range_noflush(addr, end, prot, pages);
+
+ for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) {
+ int err;
+
+ err = vmap_range_noflush(addr, addr + (1UL << page_shift),
+ __pa(page_address(pages[i])), prot,
+ page_shift);
+ if (err)
+ return err;
+
+ addr += 1UL << page_shift;
+ }
+
+ return 0;
+}
+
+static int vmap_pages_range(unsigned long addr, unsigned long end,
+ pgprot_t prot, struct page **pages, unsigned int page_shift)
+{
+ int err;
+
+ err = vmap_pages_range_noflush(addr, end, prot, pages, page_shift);
+ flush_cache_vmap(addr, end);
+ return err;
+}
+
+/**
+ * map_kernel_range_noflush - map kernel VM area with the specified pages
+ * @addr: start of the VM area to map
+ * @size: size of the VM area to map
+ * @prot: page protection flags to use
+ * @pages: pages to map
+ *
+ * Map PFN_UP(@size) pages at @addr. The VM area @addr and @size specify should
+ * have been allocated using get_vm_area() and its friends.
+ *
+ * NOTE:
+ * This function does NOT do any cache flushing. The caller is responsible for
+ * calling flush_cache_vmap() on to-be-mapped areas before calling this
+ * function.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+int map_kernel_range_noflush(unsigned long addr, unsigned long size,
+ pgprot_t prot, struct page **pages)
+{
+ return vmap_pages_range_noflush(addr, addr + size, prot, pages, PAGE_SHIFT);
+}
+
int map_kernel_range(unsigned long start, unsigned long size, pgprot_t prot,
struct page **pages)
{
@@ -2400,6 +2453,7 @@ static inline void set_area_direct_map(const struct vm_struct *area,
{
int i;

+ /* HUGE_VMALLOC passes small pages to set_direct_map */
for (i = 0; i < area->nr_pages; i++)
if (page_address(area->pages[i]))
set_direct_map(area->pages[i]);
@@ -2433,11 +2487,12 @@ static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages)
* map. Find the start and end range of the direct mappings to make sure
* the vm_unmap_aliases() flush includes the direct map.
*/
- for (i = 0; i < area->nr_pages; i++) {
+ for (i = 0; i < area->nr_pages; i += 1U << area->page_order) {
unsigned long addr = (unsigned long)page_address(area->pages[i]);
if (addr) {
+ unsigned long page_size = PAGE_SIZE << area->page_order;
start = min(addr, start);
- end = max(addr + PAGE_SIZE, end);
+ end = max(addr + page_size, end);
flush_dmap = 1;
}
}
@@ -2480,11 +2535,11 @@ static void __vunmap(const void *addr, int deallocate_pages)
if (deallocate_pages) {
int i;

- for (i = 0; i < area->nr_pages; i++) {
+ for (i = 0; i < area->nr_pages; i += 1U << area->page_order) {
struct page *page = area->pages[i];

BUG_ON(!page);
- __free_pages(page, 0);
+ __free_pages(page, area->page_order);
}
atomic_long_sub(area->nr_pages, &nr_vmalloc_pages);

@@ -2623,9 +2678,12 @@ void *vmap(struct page **pages, unsigned int count,
EXPORT_SYMBOL(vmap);

static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
- pgprot_t prot, int node)
+ pgprot_t prot, unsigned int page_shift, int node)
{
struct page **pages;
+ unsigned long addr = (unsigned long)area->addr;
+ unsigned long size = get_vm_area_size(area);
+ unsigned int page_order = page_shift - PAGE_SHIFT;
unsigned int nr_pages, array_size, i;
const gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO;
const gfp_t alloc_mask = gfp_mask | __GFP_NOWARN;
@@ -2633,7 +2691,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
0 :
__GFP_HIGHMEM;

- nr_pages = get_vm_area_size(area) >> PAGE_SHIFT;
+ nr_pages = size >> PAGE_SHIFT;
array_size = (nr_pages * sizeof(struct page *));

/* Please note that the recursion is strictly bounded. */
@@ -2652,29 +2710,29 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,

area->pages = pages;
area->nr_pages = nr_pages;
+ area->page_order = page_order;

- for (i = 0; i < area->nr_pages; i++) {
+ for (i = 0; i < area->nr_pages; i += 1U << page_order) {
struct page *page;
+ int p;

- if (node == NUMA_NO_NODE)
- page = alloc_page(alloc_mask|highmem_mask);
- else
- page = alloc_pages_node(node, alloc_mask|highmem_mask, 0);
-
+ page = alloc_pages_node(node, alloc_mask|highmem_mask, page_order);
if (unlikely(!page)) {
/* Successfully allocated i pages, free them in __vunmap() */
area->nr_pages = i;
atomic_long_add(area->nr_pages, &nr_vmalloc_pages);
goto fail;
}
- area->pages[i] = page;
+
+ for (p = 0; p < (1U << page_order); p++)
+ area->pages[i + p] = page + p;
+
if (gfpflags_allow_blocking(gfp_mask))
cond_resched();
}
atomic_long_add(area->nr_pages, &nr_vmalloc_pages);

- if (map_kernel_range((unsigned long)area->addr, get_vm_area_size(area),
- prot, pages) < 0)
+ if (vmap_pages_range(addr, addr + size, prot, pages, page_shift) < 0)
goto fail;

return area->addr;
@@ -2682,7 +2740,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
fail:
warn_alloc(gfp_mask, NULL,
"vmalloc: allocation failure, allocated %ld of %ld bytes",
- (area->nr_pages*PAGE_SIZE), area->size);
+ (area->nr_pages*PAGE_SIZE), size);
__vfree(area->addr);
return NULL;
}
@@ -2713,19 +2771,42 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
struct vm_struct *area;
void *addr;
unsigned long real_size = size;
+ unsigned long real_align = align;
+ unsigned int shift = PAGE_SHIFT;

- size = PAGE_ALIGN(size);
if (!size || (size >> PAGE_SHIFT) > totalram_pages())
goto fail;

- area = __get_vm_area_node(real_size, align, VM_ALLOC | VM_UNINITIALIZED |
+ if (vmap_allow_huge && (pgprot_val(prot) == pgprot_val(PAGE_KERNEL))) {
+ unsigned long size_per_node;
+
+ /*
+ * Try huge pages. Only try for PAGE_KERNEL allocations,
+ * others like modules don't yet expect huge pages in
+ * their allocations due to apply_to_page_range not
+ * supporting them.
+ */
+
+ size_per_node = size;
+ if (node == NUMA_NO_NODE)
+ size_per_node /= num_online_nodes();
+ if (size_per_node >= PMD_SIZE) {
+ shift = PMD_SHIFT;
+ align = max(real_align, 1UL << shift);
+ size = ALIGN(real_size, 1UL << shift);
+ }
+ }
+
+again:
+ size = PAGE_ALIGN(size);
+ area = __get_vm_area_node(size, align, VM_ALLOC | VM_UNINITIALIZED |
vm_flags, start, end, node, gfp_mask, caller);
if (!area)
goto fail;

- addr = __vmalloc_area_node(area, gfp_mask, prot, node);
+ addr = __vmalloc_area_node(area, gfp_mask, prot, shift, node);
if (!addr)
- return NULL;
+ goto fail;

/*
* In this function, newly allocated vm_struct has VM_UNINITIALIZED
@@ -2739,8 +2820,19 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
return addr;

fail:
- warn_alloc(gfp_mask, NULL,
+ if (shift > PAGE_SHIFT) {
+ free_vm_area(area);
+ shift = PAGE_SHIFT;
+ align = real_align;
+ size = real_size;
+ goto again;
+ }
+
+ if (!area) {
+ /* Warn for area allocation, page allocations already warn */
+ warn_alloc(gfp_mask, NULL,
"vmalloc: allocation failure: %lu bytes", real_size);
+ }
return NULL;
}

@@ -3739,7 +3831,7 @@ static int s_show(struct seq_file *m, void *p)
seq_printf(m, " %pS", v->caller);

if (v->nr_pages)
- seq_printf(m, " pages=%d", v->nr_pages);
+ seq_printf(m, " pages=%d order=%d", v->nr_pages, v->page_order);

if (v->phys_addr)
seq_printf(m, " phys=%pa", &v->phys_addr);
--
2.23.0