vpp_main线程通过在文件vppsrcvlibmain.c中包含#include <vppinfra/tw_timer_1t_3w_1024sl_ov.h>指定了使用1t_3w_1024sl_ov类型时间轮构建定时器。
数据结构
- [ ] vlib_node_main_t
/* 线程与定时器相关成员 */typedef struct{ ...... /* Timing wheel for scheduling time-based node dispatch. */ /* 基于时间的调度策略，依赖时间轮构建，使用的是1t_3w_1024sl_ov类型时间轮 */ void *timing_wheel; /* vpp_main线程注册的定时器的私有数据保存向量，索引来自data_from_advancing_timing_wheel */ vlib_signal_timed_event_data_t *signal_timed_event_data_pool; /* Opaque data vector added via timing_wheel_advance. */ /* 已经发生的定时事件的用户句柄保存内存 */ u32 *data_from_advancing_timing_wheel; /* CPU time of next process to be ready on timing wheel. */ f64 time_next_process_ready;/* 该值目前没有使用，根据意思是最近一个可能超时的时间 */ ......} vlib_node_main_t;- [ ] vlib_signal_timed_event_data_t
/* 定时器私有数据 */typedef struct{ u16 n_data_elts;/* 数据元素个数 */ u16 n_data_elt_bytes;/* 每个元素字节数 */ /* n_data_elts * n_data_elt_bytes 即下面union存放的数据大小*/ u32 n_data_bytes; /* Process node & event type to be used to signal event. */ /* 该事件所属协程 */ u32 process_node_index; u32 event_type_index;/* 事件类型索引，用于通知协程的事件通知机制什么事情发生了 */ /* 私有数据存放位置，数据较少时，放在静态数组inline_event_data中， ** 否则放在动态内存event_data_as_vector中 */ union { u8 inline_event_data[64 - 3 * sizeof (u32) - 2 * sizeof (u16)]; /* Vector of event data used only when data does not fit inline. */ u8 *event_data_as_vector; };}vlib_signal_timed_event_data_t;代码流程
初始化时间轮
/* Main function. */intvlib_main (vlib_main_t * volatile vm, unformat_input_t * input){ ...... /* 分配时间轮描述控制块 */ nm->timing_wheel = clib_mem_alloc_aligned (sizeof (TWT (tw_timer_wheel)), CLIB_CACHE_LINE_BYTES); /* 确保可以存放10个事件 */ vec_validate (nm->data_from_advancing_timing_wheel, 10); _vec_len (nm->data_from_advancing_timing_wheel) = 0; /* Create the process timing wheel */ /* 创建时间轮 */ TW (tw_timer_wheel_init) ((TWT (tw_timer_wheel) *) nm->timing_wheel, 0 /* no callback */ , 10e-6 /* timer period 10us */ , ~0 /* max expirations per call */ ); ...... return 0;}定时器用户ID构成原则
定时器的用户ID由两部分构成，私有数据索引和类型标志位，最低位为类型标志位：
- 1表示时间类定时器，
- 0表示协程挂起类定时器(这类定时器给协程使用，协程使用该类型定时器挂起一段时间)。
/* 判断是否为时间类定时器，直接获取最低位值 */always_inline uwordvlib_timing_wheel_data_is_timed_event (u32 d){ return d & 1;}/* 构建协程挂起事件定时器用户id */always_inline u32vlib_timing_wheel_data_set_suspended_process (u32 i){ return 0 + 2 * i;}/* 构建时间类定时器用户id */always_inline u32vlib_timing_wheel_data_set_timed_event (u32 i){ return 1 + 2 * i;}/* 获取私有数据索引 */always_inline uwordvlib_timing_wheel_data_get_index (u32 d){ return d / 2;}VPP_MAIN线程驱动时间轮
/* 参数is_main决定是主线程还是worker线程 */static_always_inline voidvlib_main_or_worker_loop (vlib_main_t * vm, int is_main){ ...... while (1) { ...... if (is_main) /* 只有主协程才会调度该时间轮 */ { /* *INDENT-OFF* */ ELOG_TYPE_DECLARE (es) = { .format = "process tw start", .format_args = "", }; ELOG_TYPE_DECLARE (ee) = { .format = "process tw end: %d", .format_args = "i4", }; /* *INDENT-ON* */ struct { int nready_procs; }*ed; /* Check if process nodes have expired from timing wheel. */ ASSERT (nm->data_from_advancing_timing_wheel != 0); if (PREDICT_FALSE (vm->elog_trace_graph_dispatch)) ed = ELOG_DATA (&vlib_global_main.elog_main, es); /* 执行定时器超时操作，查看是否有定时器超时，处理超时事件，超时句柄保存在 data_from_advancing_timing_wheel中 */ nm->data_from_advancing_timing_wheel = TW (tw_timer_expire_timers_vec) ((TWT (tw_timer_wheel) *) nm->timing_wheel, vlib_time_now (vm), nm->data_from_advancing_timing_wheel); ASSERT (nm->data_from_advancing_timing_wheel != 0); if (PREDICT_FALSE (vm->elog_trace_graph_dispatch)) { ed = ELOG_DATA (&vlib_global_main.elog_main, ee); ed->nready_procs = _vec_len (nm->data_from_advancing_timing_wheel); } /* 存在超时事件 */ if (PREDICT_FALSE(_vec_len (nm->data_from_advancing_timing_wheel) > 0)) { uword i; /* 遍历超时事件 */ for (i = 0; i < _vec_len (nm->data_from_advancing_timing_wheel); i++) { u32 d = nm->data_from_advancing_timing_wheel[i]; /* 句柄转换为索引，因为最低为为类型位，所以直接除以二 */ u32 di = vlib_timing_wheel_data_get_index (d); if (vlib_timing_wheel_data_is_timed_event (d))/* 最低位为1说明是一般定时事件 */ { vlib_signal_timed_event_data_t *te = pool_elt_at_index (nm->signal_timed_event_data_pool, di); vlib_node_t *n = vlib_get_node (vm, te->process_node_index); vlib_process_t *p = vec_elt (nm->processes, n->runtime_index); void *data; /* 通知事件处理,通知指定协程，定时事件发生了 */ data = vlib_process_signal_event_helper (nm, n, p, te->event_type_index, te->n_data_elts, te->n_data_elt_bytes); /* 透明数据拷贝 */ if (te->n_data_bytes < sizeof (te->inline_event_data)) clib_memcpy_fast (data, te->inline_event_data, te->n_data_bytes); else { clib_memcpy_fast (data, te->event_data_as_vector, te->n_data_bytes); vec_free (te->event_data_as_vector); } /* 将te从signal_timed_event_data_pool移除 */ pool_put (nm->signal_timed_event_data_pool, te); } else /* 协程类定时事件 */ { /* 处理协程定时事件，即唤醒协程 */ cpu_time_now = clib_cpu_time_now (); cpu_time_now = dispatch_suspended_process (vm, di, cpu_time_now); } } _vec_len (nm->data_from_advancing_timing_wheel) = 0; } } vlib_increment_main_loop_counter (vm); /* Record time stamp in case there are no enabled nodes and above calls do not update time stamp. */ cpu_time_now = clib_cpu_time_now (); }}协程类定时器注册
static u64dispatch_process (vlib_main_t * vm, vlib_process_t * p, vlib_frame_t * f, u64 last_time_stamp){ ...... if (is_suspend) { vlib_pending_frame_t *pf; n_vectors = 0; pool_get (nm->suspended_process_frames, pf); pf->node_runtime_index = node->runtime_index; pf->frame_index = f ? vlib_frame_index (vm, f) : ~0; pf->next_frame_index = ~0; p->n_suspends += 1;/* 统计挂起数量 */ p->suspended_process_frame_index = pf - nm->suspended_process_frames; /* 设置了使用定时器挂起标志，则通过定时器挂起该线程 */ if (p->flags & VLIB_PROCESS_IS_SUSPENDED_WAITING_FOR_CLOCK) { TWT (tw_timer_wheel) * tw = (TWT (tw_timer_wheel) *) nm->timing_wheel; p->stop_timer_handle = TW (tw_timer_start) (tw, vlib_timing_wheel_data_set_suspended_process (node->runtime_index) /* [sic] pool idex */ , 0 /* timer_id */ , p->resume_clock_interval); } } else p->flags &= ~VLIB_PROCESS_IS_RUNNING; t = clib_cpu_time_now (); vlib_elog_main_loop_event (vm, node_runtime->node_index, t, is_suspend, /* is_after */ 1); vlib_process_update_stats (vm, p, /* n_calls */ !is_suspend, /* n_vectors */ n_vectors, /* n_clocks */ t - last_time_stamp); return t;}普通定时器注册
以quic.c模块使用了vpp_main线程的定时器为例
static voidquic_update_timer (quic_ctx_t * ctx){ tw_timer_wheel_1t_3w_1024sl_ov_t *tw; int64_t next_timeout; // This timeout is in ms which is the unit of our timer next_timeout = quicly_get_first_timeout (ctx->c_quic_ctx_id.conn); tw = &quic_main.wrk_ctx[vlib_get_thread_index ()].timer_wheel; f64 next_timeout_f = ((f64) next_timeout) / 1000.f; clib_warning ("Timer set to %ld (%lf)", next_timeout, next_timeout_f); if (ctx->c_quic_ctx_id.timer_handle == QUIC_TIMER_HANDLE_INVALID) { if (next_timeout == INT64_MAX) return; ctx->c_quic_ctx_id.timer_handle = tw_timer_start_1t_3w_1024sl_ov (tw, ctx->c_c_index, 0, next_timeout_f); } else { if (next_timeout == INT64_MAX) { tw_timer_stop_1t_3w_1024sl_ov (tw, ctx->c_quic_ctx_id.timer_handle); ctx->c_quic_ctx_id.timer_handle = QUIC_TIMER_HANDLE_INVALID; } else tw_timer_update_1t_3w_1024sl_ov (tw, ctx->c_quic_ctx_id.timer_handle, next_timeout_f); }}