On 2/10/22 7:41 AM, Song Liu wrote:
bpf_prog_pack uses huge pages to reduce pressue on instruction TLB.
To guarantee allocating huge pages for bpf_prog_pack, it is necessary to
allocate memory of size PMD_SIZE * num_online_nodes().
On the other hand, if the system doesn't support huge pages, it is more
efficient to allocate PAGE_SIZE bpf_prog_pack.
Address different scenarios with more flexible bpf_prog_pack_size().
Signed-off-by: Song Liu <song@xxxxxxxxxx>
---
kernel/bpf/core.c | 47 +++++++++++++++++++++++++++--------------------
1 file changed, 27 insertions(+), 20 deletions(-)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 42d96549a804..d961a1f07a13 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -814,46 +814,53 @@ int bpf_jit_add_poke_descriptor(struct bpf_prog *prog,
* allocator. The prog_pack allocator uses HPAGE_PMD_SIZE page (2MB on x86)
* to host BPF programs.
*/
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-#define BPF_PROG_PACK_SIZE HPAGE_PMD_SIZE
-#else
-#define BPF_PROG_PACK_SIZE PAGE_SIZE
-#endif
#define BPF_PROG_CHUNK_SHIFT 6
#define BPF_PROG_CHUNK_SIZE (1 << BPF_PROG_CHUNK_SHIFT)
#define BPF_PROG_CHUNK_MASK (~(BPF_PROG_CHUNK_SIZE - 1))
-#define BPF_PROG_CHUNK_COUNT (BPF_PROG_PACK_SIZE / BPF_PROG_CHUNK_SIZE)
struct bpf_prog_pack {
struct list_head list;
void *ptr;
- unsigned long bitmap[BITS_TO_LONGS(BPF_PROG_CHUNK_COUNT)];
+ unsigned long bitmap[];
};
-#define BPF_PROG_MAX_PACK_PROG_SIZE BPF_PROG_PACK_SIZE
#define BPF_PROG_SIZE_TO_NBITS(size) (round_up(size, BPF_PROG_CHUNK_SIZE) / BPF_PROG_CHUNK_SIZE)
static DEFINE_MUTEX(pack_mutex);
static LIST_HEAD(pack_list);
+static inline int bpf_prog_pack_size(void)
+{
+ /* If vmap_allow_huge == true, use pack size of the smallest
+ * possible vmalloc huge page: PMD_SIZE * num_online_nodes().
+ * Otherwise, use pack size of PAGE_SIZE.
+ */
+ return get_vmap_allow_huge() ? PMD_SIZE * num_online_nodes() : PAGE_SIZE;
+}
Imho, this is making too many assumptions about implementation details. Can't we
just add a new module_alloc*() API instead which internally guarantees allocating
huge pages when enabled/supported (e.g. with a __weak function as fallback)?
+static inline int bpf_prog_chunk_count(void)
+{
+ return bpf_prog_pack_size() / BPF_PROG_CHUNK_SIZE;
+}
+
static struct bpf_prog_pack *alloc_new_pack(void)
{
struct bpf_prog_pack *pack;
- pack = kzalloc(sizeof(*pack), GFP_KERNEL);
+ pack = kzalloc(sizeof(*pack) + BITS_TO_BYTES(bpf_prog_chunk_count()), GFP_KERNEL);
if (!pack)
return NULL;
- pack->ptr = module_alloc(BPF_PROG_PACK_SIZE);
+ pack->ptr = module_alloc(bpf_prog_pack_size());
if (!pack->ptr) {
kfree(pack);
return NULL;
}
- bitmap_zero(pack->bitmap, BPF_PROG_PACK_SIZE / BPF_PROG_CHUNK_SIZE);
+ bitmap_zero(pack->bitmap, bpf_prog_pack_size() / BPF_PROG_CHUNK_SIZE);
list_add_tail(&pack->list, &pack_list);
set_vm_flush_reset_perms(pack->ptr);
- set_memory_ro((unsigned long)pack->ptr, BPF_PROG_PACK_SIZE / PAGE_SIZE);
- set_memory_x((unsigned long)pack->ptr, BPF_PROG_PACK_SIZE / PAGE_SIZE);
+ set_memory_ro((unsigned long)pack->ptr, bpf_prog_pack_size() / PAGE_SIZE);
+ set_memory_x((unsigned long)pack->ptr, bpf_prog_pack_size() / PAGE_SIZE);
return pack;
}
@@ -864,7 +871,7 @@ static void *bpf_prog_pack_alloc(u32 size)
unsigned long pos;
void *ptr = NULL;
- if (size > BPF_PROG_MAX_PACK_PROG_SIZE) {
+ if (size > bpf_prog_pack_size()) {
size = round_up(size, PAGE_SIZE);
ptr = module_alloc(size);
if (ptr) {
@@ -876,9 +883,9 @@ static void *bpf_prog_pack_alloc(u32 size)
}
mutex_lock(&pack_mutex);
list_for_each_entry(pack, &pack_list, list) {
- pos = bitmap_find_next_zero_area(pack->bitmap, BPF_PROG_CHUNK_COUNT, 0,
+ pos = bitmap_find_next_zero_area(pack->bitmap, bpf_prog_chunk_count(), 0,
nbits, 0);
- if (pos < BPF_PROG_CHUNK_COUNT)
+ if (pos < bpf_prog_chunk_count())
goto found_free_area;
}
@@ -904,12 +911,12 @@ static void bpf_prog_pack_free(struct bpf_binary_header *hdr)
unsigned long pos;
void *pack_ptr;
- if (hdr->size > BPF_PROG_MAX_PACK_PROG_SIZE) {
+ if (hdr->size > bpf_prog_pack_size()) {
module_memfree(hdr);
return;
}
- pack_ptr = (void *)((unsigned long)hdr & ~(BPF_PROG_PACK_SIZE - 1));
+ pack_ptr = (void *)((unsigned long)hdr & ~(bpf_prog_pack_size() - 1));
mutex_lock(&pack_mutex);
list_for_each_entry(tmp, &pack_list, list) {
@@ -926,8 +933,8 @@ static void bpf_prog_pack_free(struct bpf_binary_header *hdr)
pos = ((unsigned long)hdr - (unsigned long)pack_ptr) >> BPF_PROG_CHUNK_SHIFT;
bitmap_clear(pack->bitmap, pos, nbits);
- if (bitmap_find_next_zero_area(pack->bitmap, BPF_PROG_CHUNK_COUNT, 0,
- BPF_PROG_CHUNK_COUNT, 0) == 0) {
+ if (bitmap_find_next_zero_area(pack->bitmap, bpf_prog_chunk_count(), 0,
+ bpf_prog_chunk_count(), 0) == 0) {
list_del(&pack->list);
module_memfree(pack->ptr);
kfree(pack);
