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selftests/bpf: Fix expired UDP LRU entries in XDP LB benchmark

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populate_lru() zero-initializes atime:

    struct real_pos_lru lru = { .pos = real_idx };

connection_table_lookup() treats UDP entries with
cur_time - atime > 30s as expired, so every pre-populated entry
expires immediately.  Calibration masks this on the CPU it runs on,
but if validation migrates to another CPU:

    [udp-v4-lru-hit] COUNTER FAIL: LRU misses=1, expected 0

Initialize atime from CLOCK_MONOTONIC for UDP flows.

Fixes: a4b5ba8187 ("selftests/bpf: Add XDP load-balancer benchmark driver")
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Link: https://lore.kernel.org/r/20260520133338.3392667-3-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Puranjay Mohan 2026-05-20 06:33:31 -07:00 committed by Alexei Starovoitov
parent fa747e9f84
commit 12e896b979
1 changed files with 11 additions and 0 deletions
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11
tools/testing/selftests/bpf/benchs/bench_xdp_lb.c
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@ -563,12 +563,23 @@ static void create_per_cpu_lru_maps(struct xdp_lb_bench *skel)
nr_inner_maps = nr_cpus;
}
static __u64 ktime_get_ns(void)
{
struct timespec ts;
clock_gettime(CLOCK_MONOTONIC, &ts);
return (__u64)ts.tv_sec * 1000000000ULL + ts.tv_nsec;
}
static void populate_lru(const struct test_scenario *sc, __u32 real_idx)
{
struct real_pos_lru lru = { .pos = real_idx };
struct flow_key fk;
int i, err;
if (sc->ip_proto == IPPROTO_UDP)
lru.atime = ktime_get_ns();
build_flow_key(&fk, sc);
/* Insert into every per-CPU inner LRU so the entry is found