diff options
| author | Jesper Dangaard Brouer <brouer@redhat.com> | 2023-06-01 18:21:54 +0200 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2023-06-05 13:39:27 -0700 |
| commit | 411486626e5779bd85439282985ff3fc25a3f6d2 (patch) | |
| tree | 26c61481d517cc7b4b7e09602a073721327882b4 /net/core | |
| parent | 7793fc3babe9fea908e57f7c187ea819f9fd7e95 (diff) | |
| download | linux-411486626e5779bd85439282985ff3fc25a3f6d2.tar.gz linux-411486626e5779bd85439282985ff3fc25a3f6d2.tar.bz2 linux-411486626e5779bd85439282985ff3fc25a3f6d2.zip | |
bpf/xdp: optimize bpf_xdp_pointer to avoid reading sinfo
Currently we observed a significant performance degradation in
samples/bpf xdp1 and xdp2, due XDP multibuffer "xdp.frags" handling,
added in commit 772251742262 ("samples/bpf: fixup some tools to be able
to support xdp multibuffer").
This patch reduce the overhead by avoiding to read/load shared_info
(sinfo) memory area, when XDP packet don't have any frags. This improves
performance because sinfo is located in another cacheline.
Function bpf_xdp_pointer() is used by BPF helpers bpf_xdp_load_bytes()
and bpf_xdp_store_bytes(). As a help to reviewers, xdp_get_buff_len() can
potentially access sinfo, but it uses xdp_buff_has_frags() flags bit check
to avoid accessing sinfo in no-frags case.
The likely/unlikely instrumentation lays out asm code such that sinfo
access isn't interleaved with no-frags case (checked on GCC 12.2.1-4).
The generated asm code is more compact towards the no-frags case.
The BPF kfunc bpf_dynptr_slice() also use bpf_xdp_pointer(). Thus, it
should also take effect for that.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/168563651438.3436004.17735707525651776648.stgit@firesoul
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/filter.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index d25d52854c21..428df050d021 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -3948,20 +3948,21 @@ void bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off, void *bpf_xdp_pointer(struct xdp_buff *xdp, u32 offset, u32 len) { - struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp); u32 size = xdp->data_end - xdp->data; + struct skb_shared_info *sinfo; void *addr = xdp->data; int i; if (unlikely(offset > 0xffff || len > 0xffff)) return ERR_PTR(-EFAULT); - if (offset + len > xdp_get_buff_len(xdp)) + if (unlikely(offset + len > xdp_get_buff_len(xdp))) return ERR_PTR(-EINVAL); - if (offset < size) /* linear area */ + if (likely(offset < size)) /* linear area */ goto out; + sinfo = xdp_get_shared_info_from_buff(xdp); offset -= size; for (i = 0; i < sinfo->nr_frags; i++) { /* paged area */ u32 frag_size = skb_frag_size(&sinfo->frags[i]); |