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Message-Id: <20250831100822.1238795-3-jackzxcui1989@163.com>
Date: Sun, 31 Aug 2025 18:08:22 +0800
From: Xin Zhao <jackzxcui1989@....com>
To: willemdebruijn.kernel@...il.com,
edumazet@...gle.com,
ferenc@...es.dev
Cc: davem@...emloft.net,
kuba@...nel.org,
pabeni@...hat.com,
horms@...nel.org,
netdev@...r.kernel.org,
linux-kernel@...r.kernel.org,
Xin Zhao <jackzxcui1989@....com>
Subject: [PATCH net-next v10 2/2] net: af_packet: Use hrtimer to do the retire operation
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 <jackzxcui1989@....com>
---
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
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