Commit 2f553b03 authored by Hou Tao's avatar Hou Tao Committed by Alexei Starovoitov
Browse files

selftsets/bpf: Retry map update for non-preallocated per-cpu map 

BPF CI failed due to map_percpu_stats_percpu_hash from time to time [1].
It seems that the failure reason is per-cpu bpf memory allocator may not
be able to allocate per-cpu pointer successfully and it can not refill
free llist timely, and bpf_map_update_elem() will return -ENOMEM.

So mitigate the problem by retrying the update operation for
non-preallocated per-cpu map.

[1]: https://github.com/kernel-patches/bpf/actions/runs/6713177520/job/18244865326?pr=5909



Signed-off-by: default avatarHou Tao <houtao1@huawei.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20231101032455.3808547-4-houtao@huaweicloud.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent b9b79553

tools/testing/selftests/bpf/map_tests/map_percpu_stats.c

+19 −1
Original line number Diff line number Diff line
@@ -141,6 +141,7 @@ struct upsert_opts { 
	__u32 map_type;

	int map_fd;

	__u32 n;

	bool retry_for_nomem;

};



static int create_small_hash(void)
@@ -154,6 +155,11 @@ static int create_small_hash(void) 
	return map_fd;

}



static bool retry_for_nomem_fn(int err)

{

	return err == ENOMEM;

}



static void *patch_map_thread(void *arg)

{

	/* 8KB is enough for 1024 CPUs. And it is shared between N_THREADS. */
@@ -175,6 +181,11 @@ static void *patch_map_thread(void *arg) 
			val_ptr = &val;

		}



		/* 2 seconds may be enough ? */

		if (opts->retry_for_nomem)

			ret = map_update_retriable(opts->map_fd, &i, val_ptr, 0,

						   40, retry_for_nomem_fn);

		else

			ret = bpf_map_update_elem(opts->map_fd, &i, val_ptr, 0);

		CHECK(ret < 0, "bpf_map_update_elem", "key=%d error: %s\n", i, strerror(errno));
@@ -296,6 +307,13 @@ static void __test(int map_fd) 
	else

		opts.n /= 2;



	/* per-cpu bpf memory allocator may not be able to allocate per-cpu

	 * pointer successfully and it can not refill free llist timely, and

	 * bpf_map_update_elem() will return -ENOMEM. so just retry to mitigate

	 * the problem temporarily.

	 */

	opts.retry_for_nomem = is_percpu(opts.map_type) && (info.map_flags & BPF_F_NO_PREALLOC);



	/*

	 * Upsert keys [0, n) under some competition: with random values from

	 * N_THREADS threads. Check values, then delete all elements and check