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| author |   Eric Dumazet <edumazet@google.com> | 2020-03-16 19:12:51 -0700 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2020-03-17 21:16:35 -0700 |
| commit | 583396f4ca4d6ee5ad314ba0f4cb5b89deb75e76 (patch) | |
| tree | ad0758e5b63398640aa6eb986b9d3e524682d800 /include | |
| parent | net_sched: do not reprogram a timer about to expire (diff) | |
| download | wireguard-linux-583396f4ca4d6ee5ad314ba0f4cb5b89deb75e76.tar.xz wireguard-linux-583396f4ca4d6ee5ad314ba0f4cb5b89deb75e76.zip | |
net_sched: sch_fq: enable use of hrtimer slack
Add a new attribute to control the fq qdisc hrtimer slack.
Default is set to 10 usec.
When/if packets are throttled, fq set up an hrtimer that can
lead to one interrupt per packet in the throttled queue.
By using a timer slack, we allow better use of timer interrupts,
by giving them a chance to call multiple timer callbacks
at each hardware interrupt.
Also, giving a slack allows FQ to dequeue batches of packets
instead of a single one, thus increasing xmit_more efficiency.
This has no negative effect on the rate a TCP flow can sustain,
since each TCP flow maintains its own precise vtime (tp->tcp_wstamp_ns)
v2: added strict netlink checking (as feedback from Jakub Kicinski)
Tested:
1000 concurrent flows all using paced packets.
1,000,000 packets sent per second.
Before the patch :
$ vmstat 2 10
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 0 0 60726784 23628 3485992 0 0 138 1 977 535 0 12 87 0 0
0 0 0 60714700 23628 3485628 0 0 0 0 1568827 26462 0 22 78 0 0
1 0 0 60716012 23628 3485656 0 0 0 0 1570034 26216 0 22 78 0 0
0 0 0 60722420 23628 3485492 0 0 0 0 1567230 26424 0 22 78 0 0
0 0 0 60727484 23628 3485556 0 0 0 0 1568220 26200 0 22 78 0 0
2 0 0 60718900 23628 3485380 0 0 0 40 1564721 26630 0 22 78 0 0
2 0 0 60718096 23628 3485332 0 0 0 0 1562593 26432 0 22 78 0 0
0 0 0 60719608 23628 3485064 0 0 0 0 1563806 26238 0 22 78 0 0
1 0 0 60722876 23628 3485236 0 0 0 130 1565874 26566 0 22 78 0 0
1 0 0 60722752 23628 3484908 0 0 0 0 1567646 26247 0 22 78 0 0
After the patch, slack of 10 usec, we can see a reduction of interrupts
per second, and a small decrease of reported cpu usage.
$ vmstat 2 10
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
1 0 0 60722564 23628 3484728 0 0 133 1 696 545 0 13 87 0 0
1 0 0 60722568 23628 3484824 0 0 0 0 977278 25469 0 20 80 0 0
0 0 0 60716396 23628 3484764 0 0 0 0 979997 25326 0 20 80 0 0
0 0 0 60713844 23628 3484960 0 0 0 0 981394 25249 0 20 80 0 0
2 0 0 60720468 23628 3484916 0 0 0 0 982860 25062 0 20 80 0 0
1 0 0 60721236 23628 3484856 0 0 0 0 982867 25100 0 20 80 0 0
1 0 0 60722400 23628 3484456 0 0 0 8 982698 25303 0 20 80 0 0
0 0 0 60715396 23628 3484428 0 0 0 0 981777 25176 0 20 80 0 0
0 0 0 60716520 23628 3486544 0 0 0 36 978965 27857 0 21 79 0 0
0 0 0 60719592 23628 3486516 0 0 0 22 977318 25106 0 20 80 0 0
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
| -rw-r--r-- | include/uapi/linux/pkt_sched.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h index ea39287d59c8..7307a29a103e 100644 --- a/include/uapi/linux/pkt_sched.h +++ b/include/uapi/linux/pkt_sched.h @@ -911,6 +911,8 @@ enum { TCA_FQ_CE_THRESHOLD, /* DCTCP-like CE-marking threshold */ + TCA_FQ_TIMER_SLACK, /* timer slack */ + __TCA_FQ_MAX }; |