Use module_alloc_huge for bpf_prog_pack so that BPF programs sit on
PMD_SIZE pages. This benefits system performance by reducing iTLB miss
rate. Benchmark of a real web service workload shows this change gives
another ~0.2% performance boost on top of PAGE_SIZE bpf_prog_pack
(which improve system throughput by ~0.5%).
Also, remove set_vm_flush_reset_perms() from alloc_new_pack() and use
set_memory_[nx|rw] in bpf_prog_pack_free(). This is because
VM_FLUSH_RESET_PERMS does not work with huge pages yet. [1]
[1] https://lore.kernel.org/bpf/[email protected]/
Suggested-by: Rick Edgecombe <[email protected]>
Signed-off-by: Song Liu <[email protected]>
---
kernel/bpf/core.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 805c2ad5c793..d1f32ac354d3 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -860,7 +860,7 @@ static size_t select_bpf_prog_pack_size(void)
void *ptr;
size = BPF_HPAGE_SIZE * num_online_nodes();
- ptr = module_alloc(size);
+ ptr = module_alloc_huge(size);
/* Test whether we can get huge pages. If not just use PAGE_SIZE
* packs.
@@ -884,7 +884,7 @@ static struct bpf_prog_pack *alloc_new_pack(bpf_jit_fill_hole_t bpf_fill_ill_ins
GFP_KERNEL);
if (!pack)
return NULL;
- pack->ptr = module_alloc(bpf_prog_pack_size);
+ pack->ptr = module_alloc_huge(bpf_prog_pack_size);
if (!pack->ptr) {
kfree(pack);
return NULL;
@@ -893,7 +893,6 @@ static struct bpf_prog_pack *alloc_new_pack(bpf_jit_fill_hole_t bpf_fill_ill_ins
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);
return pack;
@@ -912,10 +911,9 @@ static void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insn
if (size > bpf_prog_pack_size) {
size = round_up(size, PAGE_SIZE);
- ptr = module_alloc(size);
+ ptr = module_alloc_huge(size);
if (ptr) {
bpf_fill_ill_insns(ptr, size);
- set_vm_flush_reset_perms(ptr);
set_memory_ro((unsigned long)ptr, size / PAGE_SIZE);
set_memory_x((unsigned long)ptr, size / PAGE_SIZE);
}
@@ -952,6 +950,8 @@ static void bpf_prog_pack_free(struct bpf_binary_header *hdr)
mutex_lock(&pack_mutex);
if (hdr->size > bpf_prog_pack_size) {
+ set_memory_nx((unsigned long)hdr, hdr->size / PAGE_SIZE);
+ set_memory_rw((unsigned long)hdr, hdr->size / PAGE_SIZE);
module_memfree(hdr);
goto out;
}
@@ -978,6 +978,8 @@ static void bpf_prog_pack_free(struct bpf_binary_header *hdr)
if (bitmap_find_next_zero_area(pack->bitmap, bpf_prog_chunk_count(), 0,
bpf_prog_chunk_count(), 0) == 0) {
list_del(&pack->list);
+ set_memory_nx((unsigned long)pack->ptr, bpf_prog_pack_size / PAGE_SIZE);
+ set_memory_rw((unsigned long)pack->ptr, bpf_prog_pack_size / PAGE_SIZE);
module_memfree(pack->ptr);
kfree(pack);
}
--
2.30.2