From d6e81f17af13491d26b7e88d0e75101b79fe80db Mon Sep 17 00:00:00 2001 From: Lorenz Bauer Date: Tue, 28 Sep 2021 10:30:59 +0100 Subject: [PATCH] bpf: do not invoke the XDP dispatcher for PROG_RUN with single repeat We have a unit test that invokes an XDP program with 1m different inputs, aka 1m BPF_PROG_RUN syscalls. We run this test concurrently with slight variations in how we generated the input. Since commit f23c4b3924d2 ("bpf: Start using the BPF dispatcher in BPF_TEST_RUN") the unit test has slowed down significantly. Digging deeper reveals that the concurrent tests are serialised in the kernel on the XDP dispatcher. This is a global resource that is protected by a mutex, on which we contend. Fix this by not calling into the XDP dispatcher if we only want to perform a single run of the BPF program. See: https://lore.kernel.org/bpf/CACAyw9_y4QumOW35qpgTbLsJ532uGq-kVW-VESJzGyiZkypnvw@mail.gmail.com/ Signed-off-by: Lorenz Bauer --- net/bpf/test_run.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index fcb2f493f710a..6593a71dba5f0 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -803,7 +803,8 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr, if (ret) goto free_data; - bpf_prog_change_xdp(NULL, prog); + if (repeat > 1) + bpf_prog_change_xdp(NULL, prog); ret = bpf_test_run(prog, &xdp, repeat, &retval, &duration, true); /* We convert the xdp_buff back to an xdp_md before checking the return * code so the reference count of any held netdevice will be decremented @@ -824,7 +825,8 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr, sizeof(struct xdp_md)); out: - bpf_prog_change_xdp(prog, NULL); + if (repeat > 1) + bpf_prog_change_xdp(prog, NULL); free_data: kfree(data); free_ctx: