linux-kernel - Re: [PATCH v2 bpf 3/3] bpf: use module_alloc_huge for bpf_prog

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Date:   Mon, 11 Apr 2022 16:52:40 -0700
From:   Song Liu <song@...nel.org>
To:     bpf <bpf@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>,
        open list <linux-kernel@...r.kernel.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        rick.p.edgecombe@...el.com, Christoph Hellwig <hch@...radead.org>,
        imbrenda@...ux.ibm.com, Luis Chamberlain <mcgrof@...nel.org>
Subject: Re: [PATCH v2 bpf 3/3] bpf: use module_alloc_huge for bpf_prog_pack

On Mon, Apr 11, 2022 at 4:41 PM Song Liu <song@...nel.org> wrote:
>
> 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.
>
> Signed-off-by: Song Liu <song@...nel.org>

I am really sorry for spamming the list twice. The first set
experienced long lag,
so I thought it didn't get through.

I also updated the commit log of 3/3, and this one is the latest version.

Thanks,
Song

> ---
>  kernel/bpf/core.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 13e9dbeeedf3..fd45bdd80a75 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(void)
>                        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;
> @@ -889,7 +889,6 @@ static struct bpf_prog_pack *alloc_new_pack(void)
>         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;
> @@ -970,7 +969,9 @@ 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);
> -               module_memfree(pack->ptr);
> +               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);
> +               vfree(pack->ptr);
>                 kfree(pack);
>         }
>  out:
> --
> 2.30.2
>
>