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Eric Dumazet a7a2563064 tcp: mitigate scheduling jitter in EDT pacing model
In commit fefa569a9d ("net_sched: sch_fq: account for schedule/timers
drifts") we added a mitigation for scheduling jitter in fq packet scheduler.

This patch does the same in TCP stack, now it is using EDT model.

Note that this mitigation is valid for both external (fq packet scheduler)
or internal TCP pacing.

This uses the same strategy than the above commit, allowing
a time credit of half the packet currently sent.

Consider following case :

An skb is sent, after an idle period of 300 usec.
The air-time (skb->len/pacing_rate) is 500 usec
Instead of setting the pacing timer to now+500 usec,
it will use now+min(500/2, 300) -> now+250usec

This is like having a token bucket with a depth of half
an skb.

Tested:

tc qdisc replace dev eth0 root pfifo_fast

Before
netperf -P0 -H remote -- -q 1000000000 # 8000Mbit
540000 262144 262144    10.00    7710.43

After :
netperf -P0 -H remote -- -q 1000000000 # 8000 Mbit
540000 262144 262144    10.00    7999.75   # Much closer to 8000Mbit target

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-10-15 22:56:42 -07:00
arch Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-10-12 21:38:46 -07:00
block blk-mq: I/O and timer unplugs are inverted in blktrace 2018-09-27 13:12:44 -06:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto DMAengine updates for v4.19-rc1 2018-08-18 15:55:59 -07:00
Documentation FDDI: defza: Add support for DEC FDDIcontroller 700 TURBOchannel adapter 2018-10-15 21:46:06 -07:00
drivers fore200e: fix missing unlock on error in bsq_audit() 2018-10-15 22:48:35 -07:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-10-12 21:38:46 -07:00
include net: extend sk_pacing_rate to unsigned long 2018-10-15 22:56:42 -07:00
init Kbuild updates for v4.19 (2nd) 2018-08-25 13:40:38 -07:00
ipc ipc/shm.c: use ERR_CAST() for shm_lock() error return 2018-10-05 16:32:04 -07:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-10-12 21:38:46 -07:00
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mm Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-10-11 12:27:47 +02:00
net tcp: mitigate scheduling jitter in EDT pacing model 2018-10-15 22:56:42 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-10-12 21:38:46 -07:00
scripts Kbuild fixes for v4.19 (2nd) 2018-10-11 19:23:07 +02:00
security Revert "uapi/linux/keyctl.h: don't use C++ reserved keyword as a struct member name" 2018-09-25 13:28:58 +02:00
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Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS FDDI: defza: Add support for DEC FDDIcontroller 700 TURBOchannel adapter 2018-10-15 21:46:06 -07:00
Makefile Kbuild fixes for v4.19 (2nd) 2018-10-11 19:23:07 +02:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.