[PATCH] net: af_packet: add af_packet hrtimer mode
From: Xin Zhao <hidden>
Date: 2025-08-06 05:52:49
Also in:
lkml
Subsystem:
networking [general], packet sockets, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Willem de Bruijn, Linus Torvalds
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. Add hrtimer mode to help compensate for the shortcomings in real-time performance. Signed-off-by: Xin Zhao <redacted> --- net/packet/Kconfig | 10 ++++++++++ net/packet/af_packet.c | 39 +++++++++++++++++++++++++++++++++++++++ net/packet/internal.h | 8 ++++++++ 3 files changed, 57 insertions(+)
diff --git a/net/packet/Kconfig b/net/packet/Kconfig
index 2997382d5..5e77ce08e 100644
--- a/net/packet/Kconfig
+++ b/net/packet/Kconfig@@ -23,3 +23,13 @@ config PACKET_DIAG help Support for PF_PACKET sockets monitoring interface used by the ss tool. If unsure, say Y. + +config PACKET_HRTIMER + tristate "Packet: use hrtimer instead of timer" + depends on PACKET + default n + help + Support hrtimer mode for PF_PACKET sockets to improve real-time + performance. The default timeout mechanism with jiffies granularity + is insufficient to meet the demands for real-time performance. + If unsure, say N.
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index bc438d0d9..5c7e4ef89 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c@@ -203,7 +203,11 @@ 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 *); +#ifdef CONFIG_PACKET_HRTIMER +static enum hrtimer_restart prb_retire_rx_blk_timer_expired(struct hrtimer *); +#else static void prb_retire_rx_blk_timer_expired(struct timer_list *); +#endif static void _prb_refresh_rx_retire_blk_timer(struct tpacket_kbdq_core *); static void prb_fill_rxhash(struct tpacket_kbdq_core *, struct tpacket3_hdr *); static void prb_clear_rxhash(struct tpacket_kbdq_core *,
@@ -581,7 +585,11 @@ static __be16 vlan_get_protocol_dgram(const struct sk_buff *skb) static void prb_del_retire_blk_timer(struct tpacket_kbdq_core *pkc) { +#ifdef CONFIG_PACKET_HRTIMER + hrtimer_cancel(&pkc->retire_blk_timer); +#else timer_delete_sync(&pkc->retire_blk_timer); +#endif } static void prb_shutdown_retire_blk_timer(struct packet_sock *po,
@@ -603,9 +611,16 @@ static void prb_setup_retire_blk_timer(struct packet_sock *po) struct tpacket_kbdq_core *pkc; pkc = GET_PBDQC_FROM_RB(&po->rx_ring); +#ifdef CONFIG_PACKET_HRTIMER + hrtimer_init(&pkc->retire_blk_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT); + pkc->retire_blk_timer.function = prb_retire_rx_blk_timer_expired; + if (pkc->tov_in_msecs == 0) + pkc->tov_in_msecs = jiffies_to_msecs(1); +#else timer_setup(&pkc->retire_blk_timer, prb_retire_rx_blk_timer_expired, 0); pkc->retire_blk_timer.expires = jiffies; +#endif } static int prb_calc_retire_blk_tmo(struct packet_sock *po,
@@ -676,7 +691,11 @@ static void init_prb_bdqc(struct packet_sock *po, else p1->retire_blk_tov = prb_calc_retire_blk_tmo(po, req_u->req3.tp_block_size); +#ifdef CONFIG_PACKET_HRTIMER + p1->tov_in_msecs = p1->retire_blk_tov; +#else p1->tov_in_jiffies = msecs_to_jiffies(p1->retire_blk_tov); +#endif p1->blk_sizeof_priv = req_u->req3.tp_sizeof_priv; rwlock_init(&p1->blk_fill_in_prog_lock);
@@ -691,8 +710,15 @@ static void init_prb_bdqc(struct packet_sock *po, */ static void _prb_refresh_rx_retire_blk_timer(struct tpacket_kbdq_core *pkc) { +#ifdef CONFIG_PACKET_HRTIMER + hrtimer_start_range_ns(&pkc->retire_blk_timer, + ms_to_ktime(pkc->tov_in_msecs), + 0, + HRTIMER_MODE_REL_SOFT); +#else mod_timer(&pkc->retire_blk_timer, jiffies + pkc->tov_in_jiffies); +#endif pkc->last_kactive_blk_num = pkc->kactive_blk_num; }
@@ -719,8 +745,15 @@ static void _prb_refresh_rx_retire_blk_timer(struct tpacket_kbdq_core *pkc) * prb_calc_retire_blk_tmo() calculates the tmo. * */ +#ifdef CONFIG_PACKET_HRTIMER +static enum hrtimer_restart prb_retire_rx_blk_timer_expired(struct hrtimer *t) +#else static void prb_retire_rx_blk_timer_expired(struct timer_list *t) +#endif { +#ifdef CONFIG_PACKET_HRTIMER + enum hrtimer_restart ret = HRTIMER_RESTART; +#endif struct packet_sock *po = timer_container_of(po, t, rx_ring.prb_bdqc.retire_blk_timer); struct tpacket_kbdq_core *pkc = GET_PBDQC_FROM_RB(&po->rx_ring);
@@ -787,9 +820,15 @@ static void prb_retire_rx_blk_timer_expired(struct timer_list *t) refresh_timer: _prb_refresh_rx_retire_blk_timer(pkc); +#ifdef CONFIG_PACKET_HRTIMER + ret = HRTIMER_RESTART; +#endif out: spin_unlock(&po->sk.sk_receive_queue.lock); +#ifdef CONFIG_PACKET_HRTIMER + return ret; +#endif } static void prb_flush_block(struct tpacket_kbdq_core *pkc1,
diff --git a/net/packet/internal.h b/net/packet/internal.h
index 1e743d031..d9f2b2492 100644
--- a/net/packet/internal.h
+++ b/net/packet/internal.h@@ -47,10 +47,18 @@ struct tpacket_kbdq_core { unsigned short retire_blk_tov; unsigned short version; +#ifdef CONFIG_PACKET_HRTIMER + unsigned long tov_in_msecs; +#else unsigned long tov_in_jiffies; +#endif /* timer to retire an outstanding block */ +#ifdef CONFIG_PACKET_HRTIMER + struct hrtimer retire_blk_timer; +#else struct timer_list retire_blk_timer; +#endif }; struct pgv {
--
2.34.1