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Subject[PATCH v5 bpf-next 2/5] bpf: use module_alloc_huge for bpf_prog_pack
Date
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/aeeeaf0b7ec63fdba55d4834d2f524d8bf05b71b.camel@intel.com/
Suggested-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Song Liu <song@kernel.org>
---
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 f023cb399e3f..83f5a98517d5 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -857,7 +857,7 @@ 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.
@@ -881,7 +881,7 @@ 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;
@@ -890,7 +890,6 @@ 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;
@@ -909,10 +908,9 @@ 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);
}
@@ -949,6 +947,8 @@ 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;
}
@@ -975,6 +975,8 @@ 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
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