Yeah, I still remember that "Who needs cpumap nowadays" (c), but anyway.
__xdp_build_skb_from_frame() missed the moment when the networking stack
became able to recycle skb pages backed by a page_pool. This was making
e.g. cpumap redirect even less effective than simple %XDP_PASS. veth was
also affected in some scenarios.
A lot of drivers use skb_mark_for_recycle() already, it's been almost
two years and seems like there are no issues in using it in the generic
code too. {__,}xdp_release_frame() can be then removed as it losts its
last user.
Page Pool becomes then zero-alloc (or almost) in the abovementioned
cases, too. Other memory type models (who needs them at this point)
have no changes.
Some numbers on 1 Xeon Platinum core bombed with 27 Mpps of 64-byte
IPv6 UDP, iavf w/XDP[0] (CONFIG_PAGE_POOL_STATS is enabled):
Plain %XDP_PASS on baseline, Page Pool driver:
src cpu Rx drops dst cpu Rx
2.1 Mpps N/A 2.1 Mpps
cpumap redirect (cross-core, w/o leaving its NUMA node) on baseline:
6.8 Mpps 5.0 Mpps 1.8 Mpps
cpumap redirect with skb PP recycling:
7.9 Mpps 5.7 Mpps 2.2 Mpps
+22% (from cpumap redir on baseline)
[0] https://github.com/alobakin/linux/commits/iavf-xdp
Alexander Lobakin (4):
selftests/bpf: robustify test_xdp_do_redirect with more payload magics
net: page_pool, skbuff: make skb_mark_for_recycle() always available
xdp: recycle Page Pool backed skbs built from XDP frames
xdp: remove unused {__,}xdp_release_frame()
include/linux/skbuff.h | 4 +--
include/net/xdp.h | 29 ---------------
net/core/xdp.c | 19 ++--------
.../bpf/progs/test_xdp_do_redirect.c | 36 +++++++++++++------
4 files changed, 30 insertions(+), 58 deletions(-)
---
>From v2[1]:
* fix the test_xdp_do_redirect selftest failing after the series: it was
relying on that %XDP_PASS frames can't be recycled on veth
(BPF CI, Alexei);
* explain "w/o leaving its node" in the cover letter (Jesper).
>From v1[2]:
* make skb_mark_for_recycle() always available, otherwise there are build
failures on non-PP systems (kbuild bot);
* 'Page Pool' -> 'page_pool' when it's about a page_pool instance, not
API (Jesper);
* expanded test system info a bit in the cover letter (Jesper).
[1] https://lore.kernel.org/bpf/20230303133232.2546004-1-aleksander.lobakin@xxxxxxxxx
[2] https://lore.kernel.org/bpf/20230301160315.1022488-1-aleksander.lobakin@xxxxxxxxx
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2.39.2
