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Message-ID: <CAL+tcoB3iwsTTt8Bpc62Zc-CoyOGRrAdAjo26XqUvFnBoqXpTw@mail.gmail.com>
Date: Wed, 24 Jul 2024 00:00:38 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, horms@...nel.org,
netdev@...r.kernel.org, Jason Xing <kernelxing@...cent.com>
Subject: Re: [RFC PATCH net-next] net: add an entry for CONFIG_NET_RX_BUSY_POLL
On Tue, Jul 23, 2024 at 11:26 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Tue, Jul 23, 2024 at 5:13 PM Jason Xing <kerneljasonxing@...il.com> wrote:
> >
> > On Tue, Jul 23, 2024 at 11:09 PM Jason Xing <kerneljasonxing@...il.com> wrote:
> > >
> > > On Tue, Jul 23, 2024 at 10:57 PM Eric Dumazet <edumazet@...gle.com> wrote:
> > > >
> > > > On Tue, Jul 23, 2024 at 3:57 PM Jason Xing <kerneljasonxing@...il.com> wrote:
> > > > >
> > > > > From: Jason Xing <kernelxing@...cent.com>
> > > > >
> > > > > When I was doing performance test on unix_poll(), I found out that
> > > > > accessing sk->sk_ll_usec when calling sock_poll()->sk_can_busy_loop()
> > > > > occupies too much time, which causes around 16% degradation. So I
> > > > > decided to turn off this config, which cannot be done apparently
> > > > > before this patch.
> > > >
> > > > Too many CONFIG_ options, distros will enable it anyway.
> > > >
> > > > In my builds, offset of sk_ll_usec is 0xe8.
> > > >
> > > > Are you using some debug options or an old tree ?
> >
> > I forgot to say: I'm running the latest kernel which I pulled around
> > two hours ago. Whatever kind of configs with/without debug options I
> > use, I can still reproduce it.
>
> Ok, please post :
>
> pahole --hex -C sock vmlinux
1) Enable the config:
$ pahole --hex -C sock vmlinux
struct sock {
struct sock_common __sk_common; /* 0 0x88 */
/* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */
__u8
__cacheline_group_begin__sock_write_rx[0]; /* 0x88 0 */
atomic_t sk_drops; /* 0x88 0x4 */
__s32 sk_peek_off; /* 0x8c 0x4 */
struct sk_buff_head sk_error_queue; /* 0x90 0x18 */
struct sk_buff_head sk_receive_queue; /* 0xa8 0x18 */
/* --- cacheline 3 boundary (192 bytes) --- */
struct {
atomic_t rmem_alloc; /* 0xc0 0x4 */
int len; /* 0xc4 0x4 */
struct sk_buff * head; /* 0xc8 0x8 */
struct sk_buff * tail; /* 0xd0 0x8 */
} sk_backlog; /* 0xc0 0x18 */
__u8
__cacheline_group_end__sock_write_rx[0]; /* 0xd8 0 */
__u8
__cacheline_group_begin__sock_read_rx[0]; /* 0xd8 0 */
struct dst_entry * sk_rx_dst; /* 0xd8 0x8 */
int sk_rx_dst_ifindex; /* 0xe0 0x4 */
u32 sk_rx_dst_cookie; /* 0xe4 0x4 */
unsigned int sk_ll_usec; /* 0xe8 0x4 */
unsigned int sk_napi_id; /* 0xec 0x4 */
u16 sk_busy_poll_budget; /* 0xf0 0x2 */
u8 sk_prefer_busy_poll; /* 0xf2 0x1 */
u8 sk_userlocks; /* 0xf3 0x1 */
int sk_rcvbuf; /* 0xf4 0x4 */
struct sk_filter * sk_filter; /* 0xf8 0x8 */
/* --- cacheline 4 boundary (256 bytes) --- */
union {
struct socket_wq * sk_wq; /* 0x100 0x8 */
struct socket_wq * sk_wq_raw; /* 0x100 0x8 */
}; /* 0x100 0x8 */
void (*sk_data_ready)(struct sock *); /*
0x108 0x8 */
long int sk_rcvtimeo; /* 0x110 0x8 */
int sk_rcvlowat; /* 0x118 0x4 */
__u8
__cacheline_group_end__sock_read_rx[0]; /* 0x11c 0 */
__u8
__cacheline_group_begin__sock_read_rxtx[0]; /* 0x11c 0 */
int sk_err; /* 0x11c 0x4 */
struct socket * sk_socket; /* 0x120 0x8 */
struct mem_cgroup * sk_memcg; /* 0x128 0x8 */
struct xfrm_policy * sk_policy[2]; /* 0x130 0x10 */
/* --- cacheline 5 boundary (320 bytes) --- */
__u8
__cacheline_group_end__sock_read_rxtx[0]; /* 0x140 0 */
__u8
__cacheline_group_begin__sock_write_rxtx[0]; /* 0x140 0 */
socket_lock_t sk_lock; /* 0x140 0x20 */
u32 sk_reserved_mem; /* 0x160 0x4 */
int sk_forward_alloc; /* 0x164 0x4 */
u32 sk_tsflags; /* 0x168 0x4 */
__u8
__cacheline_group_end__sock_write_rxtx[0]; /* 0x16c 0 */
__u8
__cacheline_group_begin__sock_write_tx[0]; /* 0x16c 0 */
int sk_write_pending; /* 0x16c 0x4 */
atomic_t sk_omem_alloc; /* 0x170 0x4 */
int sk_sndbuf; /* 0x174 0x4 */
int sk_wmem_queued; /* 0x178 0x4 */
refcount_t sk_wmem_alloc; /* 0x17c 0x4 */
/* --- cacheline 6 boundary (384 bytes) --- */
long unsigned int sk_tsq_flags; /* 0x180 0x8 */
union {
struct sk_buff * sk_send_head; /* 0x188 0x8 */
struct rb_root tcp_rtx_queue; /* 0x188 0x8 */
}; /* 0x188 0x8 */
struct sk_buff_head sk_write_queue; /* 0x190 0x18 */
u32 sk_dst_pending_confirm; /* 0x1a8 0x4 */
u32 sk_pacing_status; /* 0x1ac 0x4 */
struct page_frag sk_frag; /* 0x1b0 0x10 */
/* --- cacheline 7 boundary (448 bytes) --- */
struct timer_list sk_timer; /* 0x1c0 0x28 */
/* XXX last struct has 4 bytes of padding */
long unsigned int sk_pacing_rate; /* 0x1e8 0x8 */
atomic_t sk_zckey; /* 0x1f0 0x4 */
atomic_t sk_tskey; /* 0x1f4 0x4 */
__u8
__cacheline_group_end__sock_write_tx[0]; /* 0x1f8 0 */
__u8
__cacheline_group_begin__sock_read_tx[0]; /* 0x1f8 0 */
long unsigned int sk_max_pacing_rate; /* 0x1f8 0x8 */
/* --- cacheline 8 boundary (512 bytes) --- */
long int sk_sndtimeo; /* 0x200 0x8 */
u32 sk_priority; /* 0x208 0x4 */
u32 sk_mark; /* 0x20c 0x4 */
struct dst_entry * sk_dst_cache; /* 0x210 0x8 */
netdev_features_t sk_route_caps; /* 0x218 0x8 */
u16 sk_gso_type; /* 0x220 0x2 */
u16 sk_gso_max_segs; /* 0x222 0x2 */
unsigned int sk_gso_max_size; /* 0x224 0x4 */
gfp_t sk_allocation; /* 0x228 0x4 */
u32 sk_txhash; /* 0x22c 0x4 */
u8 sk_pacing_shift; /* 0x230 0x1 */
bool sk_use_task_frag; /* 0x231 0x1 */
__u8
__cacheline_group_end__sock_read_tx[0]; /* 0x232 0 */
u8 sk_gso_disabled:1; /* 0x232: 0 0x1 */
u8 sk_kern_sock:1; /* 0x232:0x1 0x1 */
u8 sk_no_check_tx:1; /* 0x232:0x2 0x1 */
u8 sk_no_check_rx:1; /* 0x232:0x3 0x1 */
/* XXX 4 bits hole, try to pack */
u8 sk_shutdown; /* 0x233 0x1 */
u16 sk_type; /* 0x234 0x2 */
u16 sk_protocol; /* 0x236 0x2 */
long unsigned int sk_lingertime; /* 0x238 0x8 */
/* --- cacheline 9 boundary (576 bytes) --- */
struct proto * sk_prot_creator; /* 0x240 0x8 */
rwlock_t sk_callback_lock; /* 0x248 0x8 */
int sk_err_soft; /* 0x250 0x4 */
u32 sk_ack_backlog; /* 0x254 0x4 */
u32 sk_max_ack_backlog; /* 0x258 0x4 */
kuid_t sk_uid; /* 0x25c 0x4 */
spinlock_t sk_peer_lock; /* 0x260 0x4 */
int sk_bind_phc; /* 0x264 0x4 */
struct pid * sk_peer_pid; /* 0x268 0x8 */
const struct cred * sk_peer_cred; /* 0x270 0x8 */
ktime_t sk_stamp; /* 0x278 0x8 */
/* --- cacheline 10 boundary (640 bytes) --- */
int sk_disconnects; /* 0x280 0x4 */
u8 sk_txrehash; /* 0x284 0x1 */
u8 sk_clockid; /* 0x285 0x1 */
u8 sk_txtime_deadline_mode:1; /* 0x286: 0 0x1 */
u8 sk_txtime_report_errors:1; /*
0x286:0x1 0x1 */
u8 sk_txtime_unused:6; /* 0x286:0x2 0x1 */
/* XXX 1 byte hole, try to pack */
void * sk_user_data; /* 0x288 0x8 */
void * sk_security; /* 0x290 0x8 */
struct sock_cgroup_data sk_cgrp_data; /* 0x298 0x10 */
/* XXX last struct has 2 bytes of padding */
void (*sk_state_change)(struct sock *);
/* 0x2a8 0x8 */
void (*sk_write_space)(struct sock *);
/* 0x2b0 0x8 */
void (*sk_error_report)(struct sock *);
/* 0x2b8 0x8 */
/* --- cacheline 11 boundary (704 bytes) --- */
int (*sk_backlog_rcv)(struct sock *,
struct sk_buff *); /* 0x2c0 0x8 */
void (*sk_destruct)(struct sock *); /*
0x2c8 0x8 */
struct sock_reuseport * sk_reuseport_cb; /* 0x2d0 0x8 */
struct bpf_local_storage * sk_bpf_storage; /* 0x2d8 0x8 */
struct callback_head sk_rcu
__attribute__((__aligned__(8))); /* 0x2e0 0x10 */
netns_tracker ns_tracker; /* 0x2f0 0 */
/* size: 752, cachelines: 12, members: 105 */
/* sum members: 749, holes: 1, sum holes: 1 */
/* sum bitfield members: 12 bits, bit holes: 1, sum bit holes: 4 bits */
/* paddings: 2, sum paddings: 6 */
/* forced alignments: 1 */
/* last cacheline: 48 bytes */
} __attribute__((__aligned__(8)));
2) Disable the config:
$ pahole --hex -C sock vmlinux
struct sock {
struct sock_common __sk_common; /* 0 0x88 */
/* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */
__u8
__cacheline_group_begin__sock_write_rx[0]; /* 0x88 0 */
atomic_t sk_drops; /* 0x88 0x4 */
__s32 sk_peek_off; /* 0x8c 0x4 */
struct sk_buff_head sk_error_queue; /* 0x90 0x18 */
struct sk_buff_head sk_receive_queue; /* 0xa8 0x18 */
/* --- cacheline 3 boundary (192 bytes) --- */
struct {
atomic_t rmem_alloc; /* 0xc0 0x4 */
int len; /* 0xc4 0x4 */
struct sk_buff * head; /* 0xc8 0x8 */
struct sk_buff * tail; /* 0xd0 0x8 */
} sk_backlog; /* 0xc0 0x18 */
__u8
__cacheline_group_end__sock_write_rx[0]; /* 0xd8 0 */
__u8
__cacheline_group_begin__sock_read_rx[0]; /* 0xd8 0 */
struct dst_entry * sk_rx_dst; /* 0xd8 0x8 */
int sk_rx_dst_ifindex; /* 0xe0 0x4 */
u32 sk_rx_dst_cookie; /* 0xe4 0x4 */
u8 sk_userlocks; /* 0xe8 0x1 */
/* XXX 3 bytes hole, try to pack */
int sk_rcvbuf; /* 0xec 0x4 */
struct sk_filter * sk_filter; /* 0xf0 0x8 */
union {
struct socket_wq * sk_wq; /* 0xf8 0x8 */
struct socket_wq * sk_wq_raw; /* 0xf8 0x8 */
}; /* 0xf8 0x8 */
/* --- cacheline 4 boundary (256 bytes) --- */
void (*sk_data_ready)(struct sock *); /*
0x100 0x8 */
long int sk_rcvtimeo; /* 0x108 0x8 */
int sk_rcvlowat; /* 0x110 0x4 */
__u8
__cacheline_group_end__sock_read_rx[0]; /* 0x114 0 */
__u8
__cacheline_group_begin__sock_read_rxtx[0]; /* 0x114 0 */
int sk_err; /* 0x114 0x4 */
struct socket * sk_socket; /* 0x118 0x8 */
struct mem_cgroup * sk_memcg; /* 0x120 0x8 */
struct xfrm_policy * sk_policy[2]; /* 0x128 0x10 */
__u8
__cacheline_group_end__sock_read_rxtx[0]; /* 0x138 0 */
__u8
__cacheline_group_begin__sock_write_rxtx[0]; /* 0x138 0 */
socket_lock_t sk_lock; /* 0x138 0x20 */
/* --- cacheline 5 boundary (320 bytes) was 24 bytes ago --- */
u32 sk_reserved_mem; /* 0x158 0x4 */
int sk_forward_alloc; /* 0x15c 0x4 */
u32 sk_tsflags; /* 0x160 0x4 */
__u8
__cacheline_group_end__sock_write_rxtx[0]; /* 0x164 0 */
__u8
__cacheline_group_begin__sock_write_tx[0]; /* 0x164 0 */
int sk_write_pending; /* 0x164 0x4 */
atomic_t sk_omem_alloc; /* 0x168 0x4 */
int sk_sndbuf; /* 0x16c 0x4 */
int sk_wmem_queued; /* 0x170 0x4 */
refcount_t sk_wmem_alloc; /* 0x174 0x4 */
long unsigned int sk_tsq_flags; /* 0x178 0x8 */
/* --- cacheline 6 boundary (384 bytes) --- */
union {
struct sk_buff * sk_send_head; /* 0x180 0x8 */
struct rb_root tcp_rtx_queue; /* 0x180 0x8 */
}; /* 0x180 0x8 */
struct sk_buff_head sk_write_queue; /* 0x188 0x18 */
u32 sk_dst_pending_confirm; /* 0x1a0 0x4 */
u32 sk_pacing_status; /* 0x1a4 0x4 */
struct page_frag sk_frag; /* 0x1a8 0x10 */
struct timer_list sk_timer; /* 0x1b8 0x28 */
/* XXX last struct has 4 bytes of padding */
/* --- cacheline 7 boundary (448 bytes) was 32 bytes ago --- */
long unsigned int sk_pacing_rate; /* 0x1e0 0x8 */
atomic_t sk_zckey; /* 0x1e8 0x4 */
atomic_t sk_tskey; /* 0x1ec 0x4 */
__u8
__cacheline_group_end__sock_write_tx[0]; /* 0x1f0 0 */
__u8
__cacheline_group_begin__sock_read_tx[0]; /* 0x1f0 0 */
long unsigned int sk_max_pacing_rate; /* 0x1f0 0x8 */
long int sk_sndtimeo; /* 0x1f8 0x8 */
/* --- cacheline 8 boundary (512 bytes) --- */
u32 sk_priority; /* 0x200 0x4 */
u32 sk_mark; /* 0x204 0x4 */
struct dst_entry * sk_dst_cache; /* 0x208 0x8 */
netdev_features_t sk_route_caps; /* 0x210 0x8 */
u16 sk_gso_type; /* 0x218 0x2 */
u16 sk_gso_max_segs; /* 0x21a 0x2 */
unsigned int sk_gso_max_size; /* 0x21c 0x4 */
gfp_t sk_allocation; /* 0x220 0x4 */
u32 sk_txhash; /* 0x224 0x4 */
u8 sk_pacing_shift; /* 0x228 0x1 */
bool sk_use_task_frag; /* 0x229 0x1 */
__u8
__cacheline_group_end__sock_read_tx[0]; /* 0x22a 0 */
u8 sk_gso_disabled:1; /* 0x22a: 0 0x1 */
u8 sk_kern_sock:1; /* 0x22a:0x1 0x1 */
u8 sk_no_check_tx:1; /* 0x22a:0x2 0x1 */
u8 sk_no_check_rx:1; /* 0x22a:0x3 0x1 */
/* XXX 4 bits hole, try to pack */
u8 sk_shutdown; /* 0x22b 0x1 */
u16 sk_type; /* 0x22c 0x2 */
u16 sk_protocol; /* 0x22e 0x2 */
long unsigned int sk_lingertime; /* 0x230 0x8 */
struct proto * sk_prot_creator; /* 0x238 0x8 */
/* --- cacheline 9 boundary (576 bytes) --- */
rwlock_t sk_callback_lock; /* 0x240 0x8 */
int sk_err_soft; /* 0x248 0x4 */
u32 sk_ack_backlog; /* 0x24c 0x4 */
u32 sk_max_ack_backlog; /* 0x250 0x4 */
kuid_t sk_uid; /* 0x254 0x4 */
spinlock_t sk_peer_lock; /* 0x258 0x4 */
int sk_bind_phc; /* 0x25c 0x4 */
struct pid * sk_peer_pid; /* 0x260 0x8 */
const struct cred * sk_peer_cred; /* 0x268 0x8 */
ktime_t sk_stamp; /* 0x270 0x8 */
int sk_disconnects; /* 0x278 0x4 */
u8 sk_txrehash; /* 0x27c 0x1 */
u8 sk_clockid; /* 0x27d 0x1 */
u8 sk_txtime_deadline_mode:1; /* 0x27e: 0 0x1 */
u8 sk_txtime_report_errors:1; /*
0x27e:0x1 0x1 */
u8 sk_txtime_unused:6; /* 0x27e:0x2 0x1 */
/* XXX 1 byte hole, try to pack */
/* --- cacheline 10 boundary (640 bytes) --- */
void * sk_user_data; /* 0x280 0x8 */
void * sk_security; /* 0x288 0x8 */
struct sock_cgroup_data sk_cgrp_data; /* 0x290 0x10 */
/* XXX last struct has 2 bytes of padding */
void (*sk_state_change)(struct sock *);
/* 0x2a0 0x8 */
void (*sk_write_space)(struct sock *);
/* 0x2a8 0x8 */
void (*sk_error_report)(struct sock *);
/* 0x2b0 0x8 */
int (*sk_backlog_rcv)(struct sock *,
struct sk_buff *); /* 0x2b8 0x8 */
/* --- cacheline 11 boundary (704 bytes) --- */
void (*sk_destruct)(struct sock *); /*
0x2c0 0x8 */
struct sock_reuseport * sk_reuseport_cb; /* 0x2c8 0x8 */
struct bpf_local_storage * sk_bpf_storage; /* 0x2d0 0x8 */
struct callback_head sk_rcu
__attribute__((__aligned__(8))); /* 0x2d8 0x10 */
netns_tracker ns_tracker; /* 0x2e8 0 */
/* size: 744, cachelines: 12, members: 101 */
/* sum members: 738, holes: 2, sum holes: 4 */
/* sum bitfield members: 12 bits, bit holes: 1, sum bit holes: 4 bits */
/* paddings: 2, sum paddings: 6 */
/* forced alignments: 1 */
/* last cacheline: 40 bytes */
} __attribute__((__aligned__(8)));
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