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Eric Dumazet 3bcb846ca4 net: get rid of spin_trylock() in net_tx_action() 
Note: Tom Herbert posted almost same patch 3 months back, but for
different reasons.

The reasons we want to get rid of this spin_trylock() are :

1) Under high qdisc pressure, the spin_trylock() has almost no
chance to succeed.

2) We loop multiple times in softirq handler, eventually reaching
the max retry count (10), and we schedule ksoftirqd.

Since we want to adhere more strictly to ksoftirqd being waked up in
the future (https://lwn.net/Articles/687617/), better avoid spurious
wakeups.

3) calls to __netif_reschedule() dirty the cache line containing
q->next_sched, slowing down the owner of qdisc.

4) RT kernels can not use the spin_trylock() here.

With help of busylock, we get the qdisc spinlock fast enough, and
the trylock trick brings only performance penalty.

Depending on qdisc setup, I observed a gain of up to 19 % in qdisc
performance (1016600 pps instead of 853400 pps, using prio+tbf+fq_codel)

("mpstat -I SCPU 1" is much happier now)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <tom@herbertland.com>
Acked-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
 		2016-06-07 15:32:03 -07:00
..
6lowpan 6lowpan: move mac802154 header 2016-04-13 10:41:10 +02:00
9p remove lots of IS_ERR_VALUE abuses 2016-05-27 15:26:11 -07:00
802
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8021q vlan: Propagate MAC address to VLANs 2016-05-31 11:56:48 -07:00
appletalk appletalk: fix erroneous return value 2016-02-18 14:59:34 -05:00
atm net/atm: sk_err_soft must be positive 2016-05-23 13:51:10 -07:00
ax25 ax25: add link layer header validation function 2016-03-09 22:13:01 -05:00
batman-adv batman-adv: initialize ELP orig address on secondary interfaces 2016-05-18 11:49:44 +08:00
bluetooth Bluetooth: fix power_on vs close race 2016-05-13 16:50:23 +02:00
bridge Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-05-09 15:59:24 -04:00
caif net: caif: fix misleading indentation 2016-03-14 13:09:50 -04:00
can sock: enable timestamping using control messages 2016-04-04 15:50:30 -04:00
ceph libceph: make ceph_osdc_wait_request() uninterruptible 2016-05-26 01:15:40 +02:00
core net: get rid of spin_trylock() in net_tx_action() 2016-06-07 15:32:03 -07:00
dcb
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dccp dccp: do not assume DCCP code is non preemptible 2016-05-02 17:02:25 -04:00
decnet decnet: Do not build routes to devices without decnet private data. 2016-04-10 23:01:30 -04:00
dns_resolver KEYS: Add a facility to restrict new links into a keyring 2016-04-11 22:37:37 +01:00
dsa net: dsa: Add new binding implementation 2016-06-04 14:29:55 -07:00
ethernet eth: Pull header from first fragment via eth_get_headlen 2016-02-24 13:58:05 -05:00
hsr net/hsr: Use setup_timer and mod_timer. 2016-05-16 14:00:43 -04:00
ieee802154 ieee802154: fix logic error in ieee802154_llsec_parse_dev_addr 2016-05-29 22:36:25 -07:00
ipv4 net: disable fragment reassembly if high_thresh is zero 2016-06-05 22:56:42 -04:00
ipv6 skbuff: introduce skb_gso_validate_mtu 2016-06-03 19:37:21 -04:00
ipx
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irda TTY and Serial driver update for 4.7-rc1 2016-05-20 20:57:27 -07:00
iucv af_iucv: Validate socket address length in iucv_sock_bind() 2016-01-19 14:21:08 -05:00
kcm kcm: fix a signedness in kcm_splice_read() 2016-05-19 11:26:51 -07:00
key
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l2tp net: l2tp: Make l2tp_ip6 namespace aware 2016-05-30 00:03:53 -07:00
l3mdev net: l3mdev: Allow send on enslaved interface 2016-05-09 22:33:52 -04:00
lapb net/lapb: tuse %*ph to dump buffers 2016-05-29 22:33:25 -07:00
llc Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-05-09 15:59:24 -04:00
mac80211 Some more work for 4.7, notably: 2016-05-12 11:46:58 -04:00
mac802154 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2016-03-19 10:05:34 -07:00
mpls skbuff: introduce skb_gso_validate_mtu 2016-06-03 19:37:21 -04:00
netfilter net: define gso types for IPx over IPv4 and IPv6 2016-05-20 18:03:15 -04:00
netlabel netlabel: fix a problem with netlbl_secattr_catmap_setrng() 2016-04-05 16:10:47 -04:00
netlink netlink: Fix dump skb leak/double free 2016-05-16 22:05:15 -04:00
netrom
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nfc nfc: nci: Add nci_nfcc_loopback to the nci core 2016-05-04 01:48:16 +02:00
openvswitch ovs: set name assign type of internal port 2016-06-02 18:05:47 -04:00
packet Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-04-23 18:51:33 -04:00
phonet sock: struct proto hash function may error 2016-02-11 03:54:14 -05:00
qrtr Merge tag 'qcom-soc-for-4.7-2' into net-next 2016-05-17 14:11:19 -04:00
rds Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-05-20 20:01:26 -07:00
rfkill rfkill: Use switch to demux userspace operations 2016-04-05 10:48:53 +02:00
rose
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rxrpc rxrpc: Use pr_<level> and pr_fmt, reduce object size a few KB 2016-06-03 19:41:31 -04:00
sched net sched actions: policer missing timestamp processing 2016-05-24 16:23:23 -07:00
sctp sctp: Fix warning in sctp_packet_transmit_chunk() 2016-06-03 22:53:26 -07:00
sunrpc NFS client updates for Linux 4.7 2016-05-26 10:33:33 -07:00
switchdev switchdev: pass pointer to fib_info instead of copy 2016-05-17 13:58:49 -04:00
tipc tipc: fix potential null pointer dereferences in some compat functions 2016-05-25 12:33:52 -07:00
unix constify security_path_{mkdir,mknod,symlink} 2016-03-28 00:47:27 -04:00
vmw_vsock Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-05-09 15:59:24 -04:00
wimax
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wireless mm/page_ref: use page_ref helper instead of direct modification of _count 2016-05-19 19:12:14 -07:00
x25 net: fix a kernel infoleak in x25 module 2016-05-09 22:45:33 -04:00
xfrm Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-05-09 15:59:24 -04:00
Kconfig bpf: add generic constant blinding for use in jits 2016-05-16 13:49:32 -04:00
Makefile net: Add Qualcomm IPC router 2016-05-08 23:46:14 -04:00
compat.c
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socket.c fs: poll/select/recvmmsg: use timespec64 for timeout events 2016-05-19 19:12:14 -07:00
sysctl_net.c
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