diff options
| author | Zhao Mengmeng <zhaomengmeng@kylinos.cn> | 2026-03-26 05:51:55 +0300 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2026-03-26 06:45:23 +0300 |
| commit | f546c77038ab898726e7344255217fbec382b97f (patch) | |
| tree | 46311628953d3a792ee0a3e71f09963cf8365bda /tools | |
| parent | 3eb8f022919187e2fe786f677569d2bd5a0b1915 (diff) | |
| download | linux-f546c77038ab898726e7344255217fbec382b97f.tar.xz | |
tools/sched_ext: scx_pair: fix pair_ctx indexing for CPU pairs
scx_pair sizes pair_ctx to nr_cpu_ids / 2, so valid pair_ctx keys are
dense pair indexes in the range [0, nr_cpu_ids / 2).
However, the userspace setup code stores pair_id as the first CPU number
in each pair. On an 8-CPU system with "-S 1", that produces pair IDs
0, 2, 4 and 6 for pairs [0,1], [2,3], [4,5] and [6,7]. CPUs in the
latter half then look up pair_ctx with out-of-range keys and the BPF
scheduler aborts with:
EXIT: scx_bpf_error (scx_pair.bpf.c:328: failed to lookup pairc and
in_pair_mask for cpu[5])
Assign pair_id using a dense pair counter instead so that each CPU pair
maps to a valid pair_ctx entry. Besides, reject odd CPU configuration, as
scx_pair requires all CPUs to be paired.
Fixes: f0262b102c7c ("tools/sched_ext: add scx_pair scheduler")
Signed-off-by: Zhao Mengmeng <zhaomengmeng@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/sched_ext/scx_pair.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/tools/sched_ext/scx_pair.c b/tools/sched_ext/scx_pair.c index 61fd86b44c40..41b136d43a55 100644 --- a/tools/sched_ext/scx_pair.c +++ b/tools/sched_ext/scx_pair.c @@ -48,6 +48,7 @@ int main(int argc, char **argv) struct bpf_link *link; __u64 seq = 0, ecode; __s32 stride, i, opt, outer_fd; + __u32 pair_id = 0; libbpf_set_print(libbpf_print_fn); signal(SIGINT, sigint_handler); @@ -82,6 +83,14 @@ restart: scx_pair__destroy(skel); return -1; } + + if (skel->rodata->nr_cpu_ids & 1) { + fprintf(stderr, "scx_pair requires an even CPU count, got %u\n", + skel->rodata->nr_cpu_ids); + scx_pair__destroy(skel); + return -1; + } + bpf_map__set_max_entries(skel->maps.pair_ctx, skel->rodata->nr_cpu_ids / 2); /* Resize arrays so their element count is equal to cpu count. */ @@ -109,10 +118,11 @@ restart: skel->rodata_pair_cpu->pair_cpu[i] = j; skel->rodata_pair_cpu->pair_cpu[j] = i; - skel->rodata_pair_id->pair_id[i] = i; - skel->rodata_pair_id->pair_id[j] = i; + skel->rodata_pair_id->pair_id[i] = pair_id; + skel->rodata_pair_id->pair_id[j] = pair_id; skel->rodata_in_pair_idx->in_pair_idx[i] = 0; skel->rodata_in_pair_idx->in_pair_idx[j] = 1; + pair_id++; printf("[%d, %d] ", i, j); } |