[PATCH bpf v2] uapi/bpf: Remove text about bpf_redirect_map() giving higher performance
From: Toke Høiland-Jørgensen <hidden>
Date: 2020-02-18 13:04:14
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
The performance of bpf_redirect() is now roughly the same as that of
bpf_redirect_map(). However, David Ahern pointed out that the header file
has not been updated to reflect this, and still says that a significant
performance increase is possible when using bpf_redirect_map(). Remove this
text from the bpf_redirect_map() description, and reword the description in
bpf_redirect() slightly. Also fix the 'Return' section of the
bpf_redirect_map() documentation.
Fixes: 1d233886dd90 ("xdp: Use bulking for non-map XDP_REDIRECT and consolidate code paths")
Reported-by: David Ahern <redacted>
Reviewed-by: Quentin Monnet <redacted>
Signed-off-by: Toke Høiland-Jørgensen <redacted>
---
v2:
- Keep a reference to bpf_redirect() in bpf_redirect_map() text (Quentin)
- Also fix up 'Return' section of bpf_redirect_map()
include/uapi/linux/bpf.h | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index f1d74a2bd234..22f235260a3a 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h@@ -1045,9 +1045,9 @@ union bpf_attr { * supports redirection to the egress interface, and accepts no * flag at all. * - * The same effect can be attained with the more generic - * **bpf_redirect_map**\ (), which requires specific maps to be - * used but offers better performance. + * The same effect can also be attained with the more generic + * **bpf_redirect_map**\ (), which uses a BPF map to store the + * redirect target instead of providing it directly to the helper. * Return * For XDP, the helper returns **XDP_REDIRECT** on success or * **XDP_ABORTED** on error. For other program types, the values
@@ -1611,13 +1611,11 @@ union bpf_attr { * the caller. Any higher bits in the *flags* argument must be * unset. * - * When used to redirect packets to net devices, this helper - * provides a high performance increase over **bpf_redirect**\ (). - * This is due to various implementation details of the underlying - * mechanisms, one of which is the fact that **bpf_redirect_map**\ - * () tries to send packet as a "bulk" to the device. + * See also bpf_redirect(), which only supports redirecting to an + * ifindex, but doesn't require a map to do so. * Return - * **XDP_REDIRECT** on success, or **XDP_ABORTED** on error. + * **XDP_REDIRECT** on success, or the value of the two lower bits + * of the **flags* argument on error. * * int bpf_sk_redirect_map(struct sk_buff *skb, struct bpf_map *map, u32 key, u64 flags) * Description
--
2.25.0