tmp_suning_uos_patched/Documentation
Nandita Dukkipati 6ba8a3b19e tcp: Tail loss probe (TLP)
This patch series implement the Tail loss probe (TLP) algorithm described
in http://tools.ietf.org/html/draft-dukkipati-tcpm-tcp-loss-probe-01. The
first patch implements the basic algorithm.

TLP's goal is to reduce tail latency of short transactions. It achieves
this by converting retransmission timeouts (RTOs) occuring due
to tail losses (losses at end of transactions) into fast recovery.
TLP transmits one packet in two round-trips when a connection is in
Open state and isn't receiving any ACKs. The transmitted packet, aka
loss probe, can be either new or a retransmission. When there is tail
loss, the ACK from a loss probe triggers FACK/early-retransmit based
fast recovery, thus avoiding a costly RTO. In the absence of loss,
there is no change in the connection state.

PTO stands for probe timeout. It is a timer event indicating
that an ACK is overdue and triggers a loss probe packet. The PTO value
is set to max(2*SRTT, 10ms) and is adjusted to account for delayed
ACK timer when there is only one oustanding packet.

TLP Algorithm

On transmission of new data in Open state:
  -> packets_out > 1: schedule PTO in max(2*SRTT, 10ms).
  -> packets_out == 1: schedule PTO in max(2*RTT, 1.5*RTT + 200ms)
  -> PTO = min(PTO, RTO)

Conditions for scheduling PTO:
  -> Connection is in Open state.
  -> Connection is either cwnd limited or no new data to send.
  -> Number of probes per tail loss episode is limited to one.
  -> Connection is SACK enabled.

When PTO fires:
  new_segment_exists:
    -> transmit new segment.
    -> packets_out++. cwnd remains same.

  no_new_packet:
    -> retransmit the last segment.
       Its ACK triggers FACK or early retransmit based recovery.

ACK path:
  -> rearm RTO at start of ACK processing.
  -> reschedule PTO if need be.

In addition, the patch includes a small variation to the Early Retransmit
(ER) algorithm, such that ER and TLP together can in principle recover any
N-degree of tail loss through fast recovery. TLP is controlled by the same
sysctl as ER, tcp_early_retrans sysctl.
tcp_early_retrans==0; disables TLP and ER.
		 ==1; enables RFC5827 ER.
		 ==2; delayed ER.
		 ==3; TLP and delayed ER. [DEFAULT]
		 ==4; TLP only.

The TLP patch series have been extensively tested on Google Web servers.
It is most effective for short Web trasactions, where it reduced RTOs by 15%
and improved HTTP response time (average by 6%, 99th percentile by 10%).
The transmitted probes account for <0.5% of the overall transmissions.

Signed-off-by: Nandita Dukkipati <nanditad@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2013-03-12 08:30:34 -04:00
..
ABI Merge branch 'for_linus' of git://cavan.codon.org.uk/platform-drivers-x86 2013-03-03 10:16:19 -08:00
accounting
acpi ACPI / Documentation: refer to correct file for acpi_platform_device_ids[] table 2013-02-13 13:43:02 +01:00
aoe aoe: allow user to disable target failure timeout 2012-12-17 17:15:25 -08:00
arm fbdev changes for 3.8: 2012-12-15 13:03:48 -08:00
arm64 arm64: Add simple earlyprintk support 2013-01-22 17:51:01 +00:00
auxdisplay
backlight backlight: lp855x_bl: support new LP8557 device 2013-02-21 17:22:25 -08:00
blackfin
block cfq-iosched: enable full blkcg hierarchy support 2013-01-09 08:05:11 -08:00
blockdev nbd: update documentation and link to mailinglist 2013-02-27 19:10:22 -08:00
bus-devices
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dvb [media] get_dvb_firmware: Fix the location of firmware for Terratec HTC 2013-01-01 11:18:26 -02:00
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netlabel
networking tcp: Tail loss probe (TLP) 2013-03-12 08:30:34 -04:00
nfc NFC: Update pn544 documentation 2013-01-10 01:27:46 +01:00
parisc
PCI PCI/MSI: Enable multiple MSIs with pci_enable_msi_block_auto() 2013-01-24 17:25:13 +01:00
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serial tty: Update serial core API documentation 2013-01-15 21:57:44 -08:00
sh
sound ALSA: compress: add support for gapless playback 2013-02-14 12:30:22 +01:00
spi Documentation: remove __dev* attributes. 2013-01-03 15:57:16 -08:00
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w1 w1: w1_therm: Add force-pullup option for "broken" sensors 2013-02-18 13:55:24 -08:00
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xtensa xtensa: initialize atomctl SR 2012-12-18 21:10:22 -08:00
zh_CN Driver core patches for 3.9-rc1 2013-02-21 12:05:51 -08:00
.gitignore
00-INDEX ImgTec Meta architecture changes for v3.9-rc1 2013-03-03 12:06:09 -08:00
applying-patches.txt
atomic_ops.txt Documentation: Memory barrier semantics of atomic_xchg() 2013-01-08 14:14:55 -08:00
bad_memory.txt
basic_profiling.txt
binfmt_misc.txt
braille-console.txt
bt8xxgpio.txt
btmrvl.txt
BUG-HUNTING
bus-virt-phys-mapping.txt
cachetlb.txt
Changes
circular-buffers.txt
clk.txt
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cpu-hotplug.txt
cpu-load.txt
cputopology.txt
crc32.txt
dcdbas.txt
debugging-modules.txt
debugging-via-ohci1394.txt
dell_rbu.txt
devices.txt
digsig.txt
DMA-API-HOWTO.txt Documentation/DMA-API-HOWTO.txt: fix typo 2013-02-27 19:10:23 -08:00
DMA-API.txt
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dma-buf-sharing.txt dma-buf: implement vmap refcounting in the interface logic 2013-02-27 15:13:36 +05:30
DMA-ISA-LPC.txt
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dontdiff
dynamic-debug-howto.txt dynamic_debug: dynamic hex dump 2013-01-17 12:19:09 -08:00
edac.txt
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HOWTO HOWTO: fix double words typo 2012-12-10 15:54:27 +01:00
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Intel-IOMMU.txt
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IPMI.txt ipmi: add options to disable openfirmware and PCI scanning 2013-02-27 19:10:21 -08:00
IRQ-affinity.txt
IRQ-domain.txt
IRQ.txt
irqflags-tracing.txt
isapnp.txt
java.txt
kernel-doc-nano-HOWTO.txt
kernel-docs.txt
kernel-parameters.txt ImgTec Meta architecture changes for v3.9-rc1 2013-03-03 12:06:09 -08:00
kmemcheck.txt
kmemleak.txt
kobject.txt
kprobes.txt
kref.txt
ldm.txt
local_ops.txt
lockdep-design.txt
lockstat.txt locking/stat: Fix a typo 2013-02-19 08:42:37 +01:00
lockup-watchdogs.txt
logo.gif
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memory-hotplug.txt hotplug: update nodemasks management 2012-12-12 17:38:33 -08:00
mono.txt
mutex-design.txt
nommu-mmap.txt
numastat.txt
oops-tracing.txt
padata.txt
parport-lowlevel.txt
parport.txt
percpu-rw-semaphore.txt
pi-futex.txt
pinctrl.txt drivers/pinctrl: grab default handles from device core 2013-01-23 16:39:51 +01:00
pnp.txt
preempt-locking.txt
printk-formats.txt Randy has moved 2013-03-08 15:05:34 -08:00
pwm.txt
ramoops.txt
rbtree.txt
remoteproc.txt
rfkill.txt
robust-futex-ABI.txt
robust-futexes.txt
rpmsg.txt Documentation: remove __dev* attributes. 2013-01-03 15:57:16 -08:00
rt-mutex-design.txt
rt-mutex.txt
rtc.txt
SAK.txt
SecurityBugs
serial-console.txt
sgi-ioc4.txt
sgi-visws.txt
SM501.txt
smsc_ece1099.txt
sparse.txt Documentation/sparse.txt: document context annotations for lock checking 2012-12-17 17:15:23 -08:00
spinlocks.txt
stable_api_nonsense.txt
stable_kernel_rules.txt
static-keys.txt
SubmitChecklist
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SubmittingPatches Randy has moved 2013-03-08 15:05:34 -08:00
svga.txt
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unicode.txt
unshare.txt
vfio.txt
VGA-softcursor.txt
vgaarbiter.txt
video-output.txt
vme_api.txt
volatile-considered-harmful.txt
workqueue.txt
xz.txt
zorro.txt