Files
linux/net/packet/internal.h
Xin Zhao f7460d2989 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.

Delete delete_blk_timer field, because hrtimer_cancel will check and wait
until the timer callback return and ensure never enter callback again.

Simplify the logic related to setting timeout, only update the hrtimer
expire time within the hrtimer callback, no longer update the expire time
in prb_open_block which is called by tpacket_rcv or timer callback.
Reasons why NOT update hrtimer in prb_open_block:
1) It will increase complexity to distinguish the two caller scenario.
2) hrtimer_cancel and hrtimer_start need to be called if you want to update
TMO of an already enqueued hrtimer, leading to complex shutdown logic.

One side effect of NOT update hrtimer when called by tpacket_rcv is that
a newly opened block triggered by tpacket_rcv may be retired earlier than
expected. On the other hand, if timeout is updated in prb_open_block, the
frequent reception of network packets that leads to prb_open_block being
called may cause hrtimer to be removed and enqueued repeatedly.

The retire hrtimer expiration is unconditional and periodic. If there are
numerous packet sockets on the system, please set an appropriate timeout
to avoid frequent enqueueing of hrtimers.

Reviewed-by: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Link: https://lore.kernel.org/all/20250831100822.1238795-1-jackzxcui1989@163.com/
Signed-off-by: Xin Zhao <jackzxcui1989@163.com>
Link: https://patch.msgid.link/20250908104549.204412-3-jackzxcui1989@163.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2025-09-11 18:40:06 -07:00

160 lines
3.4 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __PACKET_INTERNAL_H__
#define __PACKET_INTERNAL_H__
#include <linux/refcount.h>
struct packet_mclist {
struct packet_mclist *next;
int ifindex;
int count;
unsigned short type;
unsigned short alen;
unsigned char addr[MAX_ADDR_LEN];
struct list_head remove_list;
};
/* kbdq - kernel block descriptor queue */
struct tpacket_kbdq_core {
struct pgv *pkbdq;
unsigned int feature_req_word;
unsigned int hdrlen;
unsigned char reset_pending_on_curr_blk;
unsigned short kactive_blk_num;
unsigned short blk_sizeof_priv;
unsigned short version;
char *pkblk_start;
char *pkblk_end;
int kblk_size;
unsigned int max_frame_len;
unsigned int knum_blocks;
uint64_t knxt_seq_num;
char *prev;
char *nxt_offset;
struct sk_buff *skb;
rwlock_t blk_fill_in_prog_lock;
/* Default is set to 8ms */
#define DEFAULT_PRB_RETIRE_TOV (8)
ktime_t interval_ktime;
/* timer to retire an outstanding block */
struct hrtimer retire_blk_timer;
};
struct pgv {
char *buffer;
};
struct packet_ring_buffer {
struct pgv *pg_vec;
unsigned int head;
unsigned int frames_per_block;
unsigned int frame_size;
unsigned int frame_max;
unsigned int pg_vec_order;
unsigned int pg_vec_pages;
unsigned int pg_vec_len;
unsigned int __percpu *pending_refcnt;
union {
unsigned long *rx_owner_map;
struct tpacket_kbdq_core prb_bdqc;
};
};
extern struct mutex fanout_mutex;
#define PACKET_FANOUT_MAX (1 << 16)
struct packet_fanout {
possible_net_t net;
unsigned int num_members;
u32 max_num_members;
u16 id;
u8 type;
u8 flags;
union {
atomic_t rr_cur;
struct bpf_prog __rcu *bpf_prog;
};
struct list_head list;
spinlock_t lock;
refcount_t sk_ref;
struct packet_type prot_hook ____cacheline_aligned_in_smp;
struct sock __rcu *arr[] __counted_by(max_num_members);
};
struct packet_rollover {
int sock;
atomic_long_t num;
atomic_long_t num_huge;
atomic_long_t num_failed;
#define ROLLOVER_HLEN (L1_CACHE_BYTES / sizeof(u32))
u32 history[ROLLOVER_HLEN] ____cacheline_aligned;
} ____cacheline_aligned_in_smp;
struct packet_sock {
/* struct sock has to be the first member of packet_sock */
struct sock sk;
struct packet_fanout *fanout;
union tpacket_stats_u stats;
struct packet_ring_buffer rx_ring;
struct packet_ring_buffer tx_ring;
int copy_thresh;
spinlock_t bind_lock;
struct mutex pg_vec_lock;
unsigned long flags;
int ifindex; /* bound device */
u8 vnet_hdr_sz;
__be16 num;
struct packet_rollover *rollover;
struct packet_mclist *mclist;
atomic_long_t mapped;
enum tpacket_versions tp_version;
unsigned int tp_hdrlen;
unsigned int tp_reserve;
unsigned int tp_tstamp;
struct completion skb_completion;
struct net_device __rcu *cached_dev;
struct packet_type prot_hook ____cacheline_aligned_in_smp;
atomic_t tp_drops ____cacheline_aligned_in_smp;
};
#define pkt_sk(ptr) container_of_const(ptr, struct packet_sock, sk)
enum packet_sock_flags {
PACKET_SOCK_ORIGDEV,
PACKET_SOCK_AUXDATA,
PACKET_SOCK_TX_HAS_OFF,
PACKET_SOCK_TP_LOSS,
PACKET_SOCK_RUNNING,
PACKET_SOCK_PRESSURE,
PACKET_SOCK_QDISC_BYPASS,
};
static inline void packet_sock_flag_set(struct packet_sock *po,
enum packet_sock_flags flag,
bool val)
{
if (val)
set_bit(flag, &po->flags);
else
clear_bit(flag, &po->flags);
}
static inline bool packet_sock_flag(const struct packet_sock *po,
enum packet_sock_flags flag)
{
return test_bit(flag, &po->flags);
}
#endif