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Date: Wed, 9 Mar 2022 18:04:47 +0000
From: Song Liu <songliubraving@...com>
To: Song Liu <song@...nel.org>
CC: bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Kernel Team <Kernel-team@...com>,
"edumazet@...gle.com" <edumazet@...gle.com>
Subject: Re: [PATCH v2 bpf-next] bpf: select proper size for bpf_prog_pack
> On Mar 8, 2022, at 11:53 AM, Song Liu <song@...nel.org> wrote:
>
> Using HPAGE_PMD_SIZE as the size for bpf_prog_pack is not ideal in some
> cases. Specifically, for NUMA systems, __vmalloc_node_range requires
> PMD_SIZE * num_online_nodes() to allocate huge pages. Also, if the system
> does not support huge pages (i.e., with cmdline option nohugevmalloc), it
> is better to use PAGE_SIZE packs.
>
> Add logic to select proper size for bpf_prog_pack. This solution is not
> ideal, as it makes assumption about the behavior of module_alloc and
> __vmalloc_node_range. However, it appears to be the easiest solution as
> it doesn't require changes in module_alloc and vmalloc code.
>
> Fixes: 57631054fae6 ("bpf: Introduce bpf_prog_pack allocator")
> Signed-off-by: Song Liu <song@...nel.org>
I messed something up... Please ignore this version. I will send v3
soon.
Song
>
> ---
> Changes v1 => v2:
> 1. Fix case with first program > PAGE_SIZE. (Daniel)
> 2. Add Fixes tag.
> 3. Remove a inline to avoid netdev/source_inline error.
> ---
> kernel/bpf/core.c | 75 ++++++++++++++++++++++++++++++++---------------
> 1 file changed, 51 insertions(+), 24 deletions(-)
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index ab630f773ec1..f039c1f7e5dd 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -33,6 +33,7 @@
> #include <linux/extable.h>
> #include <linux/log2.h>
> #include <linux/bpf_verifier.h>
> +#include <linux/nodemask.h>
>
> #include <asm/barrier.h>
> #include <asm/unaligned.h>
> @@ -814,15 +815,9 @@ 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;
> @@ -830,30 +825,59 @@ struct bpf_prog_pack {
> 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 size_t bpf_prog_pack_size = -1;
> +
> +static int bpf_prog_chunk_count(void)
> +{
> + WARN_ON_ONCE(bpf_prog_pack_size == -1);
> + return bpf_prog_pack_size / BPF_PROG_CHUNK_SIZE;
> +}
> +
> static DEFINE_MUTEX(pack_mutex);
> static LIST_HEAD(pack_list);
>
> +static size_t select_bpf_prog_pack_size(void)
> +{
> + size_t size;
> + void *ptr;
> +
> + size = PMD_SIZE * num_online_nodes() - 1;
> + ptr = module_alloc(size);
> +
> + /* Test whether we can get huge pages. If not just use PAGE_SIZE
> + * packs.
> + */
> + if (!ptr || !is_vm_area_hugepages(ptr))
> + size = PAGE_SIZE;
> +
> + vfree(ptr);
> + return size;
> +}
> +
> static struct bpf_prog_pack *alloc_new_pack(void)
> {
> struct bpf_prog_pack *pack;
> + void *ptr;
>
> - pack = kzalloc(sizeof(*pack) + BITS_TO_BYTES(BPF_PROG_CHUNK_COUNT), GFP_KERNEL);
> - if (!pack)
> + ptr = module_alloc(bpf_prog_pack_size);
> + if (!ptr)
> return NULL;
> - pack->ptr = module_alloc(BPF_PROG_PACK_SIZE);
> - if (!pack->ptr) {
> - kfree(pack);
> +
> + pack = kzalloc(struct_size(pack, bitmap, BITS_TO_LONGS(bpf_prog_chunk_count())),
> + GFP_KERNEL);
> + if (!pack) {
> + vfree(ptr);
> return NULL;
> }
> - bitmap_zero(pack->bitmap, BPF_PROG_PACK_SIZE / BPF_PROG_CHUNK_SIZE);
> + pack->ptr = ptr;
> + 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 +888,11 @@ static void *bpf_prog_pack_alloc(u32 size)
> unsigned long pos;
> void *ptr = NULL;
>
> - if (size > BPF_PROG_MAX_PACK_PROG_SIZE) {
> + mutex_lock(&pack_mutex);
> + if (bpf_prog_pack_size == -1)
> + bpf_prog_pack_size = select_bpf_prog_pack_size();
> +
> + if (size > bpf_prog_pack_size) {
> size = round_up(size, PAGE_SIZE);
> ptr = module_alloc(size);
> if (ptr) {
> @@ -872,13 +900,12 @@ static void *bpf_prog_pack_alloc(u32 size)
> set_memory_ro((unsigned long)ptr, size / PAGE_SIZE);
> set_memory_x((unsigned long)ptr, size / PAGE_SIZE);
> }
> - return ptr;
> + goto out;
> }
> - 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 +931,12 @@ 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 +953,8 @@ 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);
> --
> 2.30.2
>
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