Following the recent upgrade of one of our BPF programs, we encountered significant latency spikes affecting other applications running on the same host. After thorough investigation, we identified that these spikes were primarily caused by the prolonged duration required to free a non-preallocated htab with approximately 2 million keys. Notably, our kernel configuration lacks the presence of CONFIG_PREEMPT. In scenarios where kernel execution extends excessively, other threads might be starved of CPU time, resulting in latency issues across the system. To mitigate this, we've adopted a proactive approach by incorporating cond_resched() calls within the kernel code. This ensures that during lengthy kernel operations, the scheduler is invoked periodically to provide opportunities for other threads to execute. Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx> --- v2: Call cond_resched() in the outer loop (Yonghong) --- kernel/bpf/hashtab.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 3a088a5349bc..e81059faae63 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -1490,6 +1490,7 @@ static void delete_all_elements(struct bpf_htab *htab) hlist_nulls_del_rcu(&l->hash_node); htab_elem_free(htab, l); } + cond_resched(); } migrate_enable(); } -- 2.39.1
