In a system with high real-time requirements, the timeout mechanism of ordinary timers with jiffies granularity is insufficient to meet the demands for real-time performance. Meanwhile, the optimization of CPU usage with af_packet is quite significant. Use hrtimer instead of timer to help compensate for the shortcomings in real-time performance. In HZ=100 or HZ=250 system, the update of TP_STATUS_USER is not real-time enough, with fluctuations reaching over 8ms (on a system with HZ=250). This is unacceptable in some high real-time systems that require timely processing of network packets. By replacing it with hrtimer, if a timeout of 2ms is set, the update of TP_STATUS_USER can be stabilized to within 3 ms. Signed-off-by: Xin Zhao --- Changes in v8: - Simplify the logic related to setting timeout. Changes in v7: - Only update the hrtimer expire time within the hrtimer callback. Changes in v1: - Do not add another config for the current changes. --- net/packet/af_packet.c | 79 +++++++++--------------------------------- net/packet/diag.c | 2 +- net/packet/internal.h | 6 ++-- 3 files changed, 20 insertions(+), 67 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index d4eb4a4fe..3e3bb4216 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -203,8 +203,7 @@ static void prb_retire_current_block(struct tpacket_kbdq_core *, static int prb_queue_frozen(struct tpacket_kbdq_core *); static void prb_open_block(struct tpacket_kbdq_core *, struct tpacket_block_desc *); -static void prb_retire_rx_blk_timer_expired(struct timer_list *); -static void _prb_refresh_rx_retire_blk_timer(struct tpacket_kbdq_core *); +static enum hrtimer_restart prb_retire_rx_blk_timer_expired(struct hrtimer *); static void prb_fill_rxhash(struct tpacket_kbdq_core *, struct tpacket3_hdr *); static void prb_clear_rxhash(struct tpacket_kbdq_core *, struct tpacket3_hdr *); @@ -579,33 +578,13 @@ static __be16 vlan_get_protocol_dgram(const struct sk_buff *skb) return proto; } -static void prb_del_retire_blk_timer(struct tpacket_kbdq_core *pkc) -{ - timer_delete_sync(&pkc->retire_blk_timer); -} - static void prb_shutdown_retire_blk_timer(struct packet_sock *po, struct sk_buff_head *rb_queue) { struct tpacket_kbdq_core *pkc; pkc = GET_PBDQC_FROM_RB(&po->rx_ring); - - spin_lock_bh(&rb_queue->lock); - pkc->delete_blk_timer = 1; - spin_unlock_bh(&rb_queue->lock); - - prb_del_retire_blk_timer(pkc); -} - -static void prb_setup_retire_blk_timer(struct packet_sock *po) -{ - struct tpacket_kbdq_core *pkc; - - pkc = GET_PBDQC_FROM_RB(&po->rx_ring); - timer_setup(&pkc->retire_blk_timer, prb_retire_rx_blk_timer_expired, - 0); - pkc->retire_blk_timer.expires = jiffies; + hrtimer_cancel(&pkc->retire_blk_timer); } static int prb_calc_retire_blk_tmo(struct packet_sock *po, @@ -671,29 +650,22 @@ static void init_prb_bdqc(struct packet_sock *po, p1->version = po->tp_version; po->stats.stats3.tp_freeze_q_cnt = 0; if (req_u->req3.tp_retire_blk_tov) - p1->retire_blk_tov = req_u->req3.tp_retire_blk_tov; + p1->interval_ktime = ms_to_ktime(req_u->req3.tp_retire_blk_tov); else - p1->retire_blk_tov = prb_calc_retire_blk_tmo(po, - req_u->req3.tp_block_size); - p1->tov_in_jiffies = msecs_to_jiffies(p1->retire_blk_tov); + p1->interval_ktime = ms_to_ktime(prb_calc_retire_blk_tmo(po, + req_u->req3.tp_block_size)); p1->blk_sizeof_priv = req_u->req3.tp_sizeof_priv; rwlock_init(&p1->blk_fill_in_prog_lock); p1->max_frame_len = p1->kblk_size - BLK_PLUS_PRIV(p1->blk_sizeof_priv); prb_init_ft_ops(p1, req_u); - prb_setup_retire_blk_timer(po); + hrtimer_setup(&p1->retire_blk_timer, prb_retire_rx_blk_timer_expired, + CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT); + hrtimer_start(&p1->retire_blk_timer, p1->interval_ktime, + HRTIMER_MODE_REL_SOFT); prb_open_block(p1, pbd); } -/* Do NOT update the last_blk_num first. - * Assumes sk_buff_head lock is held. - */ -static void _prb_refresh_rx_retire_blk_timer(struct tpacket_kbdq_core *pkc) -{ - mod_timer(&pkc->retire_blk_timer, - jiffies + pkc->tov_in_jiffies); -} - /* * Timer logic: * 1) We refresh the timer only when we open a block. @@ -717,7 +689,7 @@ static void _prb_refresh_rx_retire_blk_timer(struct tpacket_kbdq_core *pkc) * prb_calc_retire_blk_tmo() calculates the tmo. * */ -static void prb_retire_rx_blk_timer_expired(struct timer_list *t) +static enum hrtimer_restart prb_retire_rx_blk_timer_expired(struct hrtimer *t) { struct packet_sock *po = timer_container_of(po, t, rx_ring.prb_bdqc.retire_blk_timer); @@ -730,9 +702,6 @@ static void prb_retire_rx_blk_timer_expired(struct timer_list *t) frozen = prb_queue_frozen(pkc); pbd = GET_CURR_PBLOCK_DESC_FROM_CORE(pkc); - if (unlikely(pkc->delete_blk_timer)) - goto out; - /* We only need to plug the race when the block is partially filled. * tpacket_rcv: * lock(); increment BLOCK_NUM_PKTS; unlock() @@ -749,26 +718,16 @@ static void prb_retire_rx_blk_timer_expired(struct timer_list *t) } if (!frozen) { - if (!BLOCK_NUM_PKTS(pbd)) { - /* An empty block. Just refresh the timer. */ - goto refresh_timer; + if (BLOCK_NUM_PKTS(pbd)) { + /* Not an empty block. Need retire the block. */ + prb_retire_current_block(pkc, po, TP_STATUS_BLK_TMO); + prb_dispatch_next_block(pkc, po); } - prb_retire_current_block(pkc, po, TP_STATUS_BLK_TMO); - if (!prb_dispatch_next_block(pkc, po)) - goto refresh_timer; - else - goto out; } else { /* Case 1. Queue was frozen because user-space was * lagging behind. */ - if (prb_curr_blk_in_use(pbd)) { - /* - * Ok, user-space is still behind. - * So just refresh the timer. - */ - goto refresh_timer; - } else { + if (!prb_curr_blk_in_use(pbd)) { /* Case 2. queue was frozen,user-space caught up, * now the link went idle && the timer fired. * We don't have a block to close.So we open this @@ -777,15 +736,12 @@ static void prb_retire_rx_blk_timer_expired(struct timer_list *t) * Thawing/timer-refresh is a side effect. */ prb_open_block(pkc, pbd); - goto out; } } -refresh_timer: - _prb_refresh_rx_retire_blk_timer(pkc); - -out: + hrtimer_forward_now(&pkc->retire_blk_timer, pkc->interval_ktime); spin_unlock(&po->sk.sk_receive_queue.lock); + return HRTIMER_RESTART; } static void prb_flush_block(struct tpacket_kbdq_core *pkc1, @@ -917,7 +873,6 @@ static void prb_open_block(struct tpacket_kbdq_core *pkc1, pkc1->pkblk_end = pkc1->pkblk_start + pkc1->kblk_size; prb_thaw_queue(pkc1); - _prb_refresh_rx_retire_blk_timer(pkc1); smp_wmb(); } diff --git a/net/packet/diag.c b/net/packet/diag.c index 6ce1dcc28..c8f43e0c1 100644 --- a/net/packet/diag.c +++ b/net/packet/diag.c @@ -83,7 +83,7 @@ static int pdiag_put_ring(struct packet_ring_buffer *ring, int ver, int nl_type, pdr.pdr_frame_nr = ring->frame_max + 1; if (ver > TPACKET_V2) { - pdr.pdr_retire_tmo = ring->prb_bdqc.retire_blk_tov; + pdr.pdr_retire_tmo = ktime_to_ms(ring->prb_bdqc.interval_ktime); pdr.pdr_sizeof_priv = ring->prb_bdqc.blk_sizeof_priv; pdr.pdr_features = ring->prb_bdqc.feature_req_word; } else { diff --git a/net/packet/internal.h b/net/packet/internal.h index d367b9f93..f8cfd9213 100644 --- a/net/packet/internal.h +++ b/net/packet/internal.h @@ -20,7 +20,6 @@ struct tpacket_kbdq_core { unsigned int feature_req_word; unsigned int hdrlen; unsigned char reset_pending_on_curr_blk; - unsigned char delete_blk_timer; unsigned short kactive_blk_num; unsigned short blk_sizeof_priv; @@ -39,12 +38,11 @@ struct tpacket_kbdq_core { /* Default is set to 8ms */ #define DEFAULT_PRB_RETIRE_TOV (8) - unsigned short retire_blk_tov; + ktime_t interval_ktime; unsigned short version; - unsigned long tov_in_jiffies; /* timer to retire an outstanding block */ - struct timer_list retire_blk_timer; + struct hrtimer retire_blk_timer; }; struct pgv { -- 2.34.1