Yuchung Cheng f672258391 tcp: track min RTT using windowed min-filter ... Kathleen Nichols' algorithm for tracking the minimum RTT of a data stream over some measurement window. It uses constant space and constant time per update. Yet it almost always delivers the same minimum as an implementation that has to keep all the data in the window. The measurement window is tunable via sysctl.net.ipv4.tcp_min_rtt_wlen with a default value of 5 minutes. The algorithm keeps track of the best, 2nd best & 3rd best min values, maintaining an invariant that the measurement time of the n'th best >= n-1'th best. It also makes sure that the three values are widely separated in the time window since that bounds the worse case error when that data is monotonically increasing over the window. Upon getting a new min, we can forget everything earlier because it has no value - the new min is less than everything else in the window by definition and it's the most recent. So we restart fresh on every new min and overwrites the 2nd & 3rd choices. The same property holds for the 2nd & 3rd best. Therefore we have to maintain two invariants to maximize the information in the samples, one on values (1st.v <= 2nd.v <= 3rd.v) and the other on times (now-win <=1st.t <= 2nd.t <= 3rd.t <= now). These invariants determine the structure of the code The RTT input to the windowed filter is the minimum RTT measured from ACK or SACK, or as the last resort from TCP timestamps. The accessor tcp_min_rtt() returns the minimum RTT seen in the window. ~0U indicates it is not available. The minimum is 1usec even if the true RTT is below that. Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>		2015-10-21 07:00:43 -07:00
..
ABI	xen: features and fixes for 4.3-rc0	2015-09-08 11:46:48 -07:00
accounting
acpi	ACPI / Documentation: Update method tracing documentation.	2015-08-07 02:42:22 +02:00
aoe
arm	ARM: SoC platform updates for v4.3	2015-09-01 12:18:40 -07:00
arm64	arm64/Documentation: clarify wording regarding memory below the Image	2015-07-29 18:32:10 +01:00
auxdisplay
backlight
blackfin
block	Documentation: update notes in biovecs about arbitrarily sized bios	2015-08-13 12:32:07 -06:00
blockdev	zsmalloc: account the number of compacted pages	2015-09-08 15:35:28 -07:00
bus-devices
cdrom
cgroups	Merge branch 'for-4.3/blkcg' of git://git.kernel.dk/linux-block	2015-09-10 18:56:14 -07:00
cma
connector
console
cpu-freq	cpufreq: remove redundant CPUFREQ_INCOMPATIBLE notifier event	2015-09-01 15:50:38 +02:00
cpuidle
cris
crypto
development-process
device-mapper	dm snapshot: add new persistent store option to support overflow	2015-10-09 16:57:03 -04:00
devicetree	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2015-10-20 06:08:27 -07:00
dmaengine	Documentation: dmaengine: Add DMA_CTRL_REUSE documentation	2015-08-17 13:46:22 +05:30
DocBook	pwm: Changes for v4.3-rc1	2015-09-09 10:55:32 -07:00
driver-model
dvb
early-userspace
EDID
extcon
fault-injection	futex: Fault/error injection capabilities	2015-07-20 11:45:45 +02:00
fb	Documentation/fb: add documentation for sm712fb	2015-08-07 15:05:01 -07:00
features	Metag architecture changes for v4.3	2015-09-09 10:27:59 -07:00
filesystems	ipconfig: send Client-identifier in DHCP requests	2015-10-18 19:23:52 -07:00
firmware_class
fmc
frv
gpio	Documentation: gpio: Explain that <function>-gpio is also supported	2015-09-14 09:12:03 +02:00
hid
hwmon	hwmon: (nct6775) Add support for NCT6793D	2015-09-12 19:43:02 -07:00
i2c	i2c: support 10 bit and slave addresses in sysfs 'new_device'	2015-08-24 14:05:15 +02:00
ia64
ide
infiniband	IB/hfi1: add driver files	2015-08-28 22:59:36 -04:00
input	Input: fix typo in MT documentation	2015-09-19 11:39:02 -07:00
ioctl	platform-drivers-x86 for 4.3-1	2015-09-08 16:26:18 -07:00
isdn
ja_JP	Doc: ja_JP: Fix typo in HOWTO	2015-06-08 16:43:09 -06:00
kbuild	modsign: Allow password to be specified for signing key	2015-08-07 16:26:14 +01:00
kdump
ko_KR
laptops	Move freefall program from Documentation/ to tools/	2015-06-08 16:42:07 -06:00
leds	Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/cooloney/linux-leds	2015-07-01 19:09:11 -07:00
locking
m68k
memory-devices
metag
mic	Char/Misc driver patches for 4.2-rc1	2015-06-26 14:51:15 -07:00
mips
misc-devices	mei: add async event notification ioctls	2015-08-03 17:30:00 -07:00
mmc
mn10300
mtd
namespaces
netlabel
networking	tcp: track min RTT using windowed min-filter	2015-10-21 07:00:43 -07:00
nfc	NFC: Fix typo in nfc-hci.txt	2015-06-08 23:15:45 +02:00
nios2
nvdimm	libnvdimm: Non-Volatile Devices	2015-06-26 11:23:38 -04:00
nvmem	Documentation: nvmem: add nvmem api level and how-to doc	2015-08-05 13:43:45 -07:00
parisc
PCI
pcmcia	pcmcia: Fix typo in locking documentation	2015-08-07 14:34:58 +02:00
phy
platform
power	PCI / PM: Update runtime PM documentation for PCI devices	2015-09-25 02:48:44 +02:00
powerpc	SCSI misc on 20150901	2015-09-02 12:22:54 -07:00
pps	Doc: pps: Fix file name in pps.txt	2015-07-14 12:35:42 -06:00
prctl	Documentation/prctl: don't build tsc tests when cross compiling	2015-06-22 16:05:04 -06:00
pti
ptp	testptp: Silence compiler warnings on ppc64	2015-09-29 21:16:56 -07:00
rapidio
RCU	Merge branches 'doc.2015.07.15a' and 'torture.2015.07.15a' into HEAD	2015-08-04 08:42:02 -07:00
s390	KVM: s390: remove outdated documentation	2015-07-29 11:02:35 +02:00
scheduler
scsi	Merge branch 'for-4.2/sg' of git://git.kernel.dk/linux-block	2015-06-25 15:22:36 -07:00
security	Merge branch 'smack-for-4.3' of https://github.com/cschaufler/smack-next into next	2015-08-11 11:18:53 +10:00
serial	Doc: serial-rs485.txt: update RS485 driver interface	2015-06-12 17:39:51 -07:00
sh
sound	Doc: sound:oss: Fix typo in sound/oss	2015-06-09 17:23:00 +02:00
spi
sysctl	net: qdisc: enhance default_qdisc documentation	2015-09-17 16:09:22 -07:00
target	Documentation/target: Fix tcm_mod_builder.py build breakage	2015-07-24 17:48:55 -07:00
thermal	thermal: power_allocator: relax the requirement of two passive trip points	2015-09-14 07:41:45 -07:00
timers
tpm
trace	Mostly this is just clean ups and micro optimizations.	2015-09-08 14:04:14 -07:00
usb	Revert "usb: interface authorization: Documentation part"	2015-08-18 09:57:15 -07:00
vDSO	Documentation/vDSO: don't build tests when cross compiling	2015-06-22 16:04:57 -06:00
video4linux	[media] Documentation: update cardlists	2015-06-09 18:43:47 -03:00
virtual	Patch queue for ppc - 2015-08-22	2015-08-22 14:57:59 -07:00
vm	proc: export idle flag via kpageflags	2015-09-10 13:29:01 -07:00
w1
watchdog	Documentation/watchdog: add timeout and ping rate control to watchdog-test.c	2015-09-09 21:33:36 +02:00
wimax
x86	Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2015-09-01 10:07:40 -07:00
xtensa
zh_CN	Documentation updates for 4.2	2015-06-24 20:01:36 -07:00
00-INDEX
adding-syscalls.txt	Documentation: describe how to add a system call	2015-08-13 17:54:06 -06:00
applying-patches.txt
assoc_array.txt
atomic_ops.txt	locking/Documentation: Clarify failed cmpxchg() memory ordering semantics	2015-08-03 10:57:09 +02:00
bad_memory.txt
basic_profiling.txt
bcache.txt
binfmt_misc.txt
braille-console.txt
bt8xxgpio.txt
btmrvl.txt
BUG-HUNTING
bus-virt-phys-mapping.txt
cachetlb.txt
Changes	MODSIGN: Change from CMS to PKCS#7 signing if the openssl is too old	2015-09-25 16:31:46 +01:00
circular-buffers.txt
clk.txt	clk: change clk_ops' ->determine_rate() prototype	2015-07-27 18:12:01 -07:00
coccinelle.txt
CodeOfConflict
CodingStyle	Documentation: CodingStyle: remove broken links in the References section	2015-07-10 13:54:34 -06:00
cpu-hotplug.txt
cpu-load.txt
cputopology.txt
crc32.txt
dcdbas.txt
debugging-modules.txt
debugging-via-ohci1394.txt	Doc: Change wikipedia's URL from http to https	2015-06-22 10:14:05 -06:00
dell_rbu.txt
devices.txt
digsig.txt
DMA-API-HOWTO.txt	Documentation updates for 4.2	2015-06-24 20:01:36 -07:00
DMA-API.txt	mm: add dma_pool_zalloc() call to DMA API	2015-09-08 15:35:28 -07:00
DMA-attributes.txt
dma-buf-sharing.txt
DMA-ISA-LPC.txt
dontdiff
dynamic-debug-howto.txt
edac.txt	EDAC: Update Documentation/edac.txt	2015-06-24 18:17:40 +02:00
efi-stub.txt
eisa.txt
email-clients.txt	fix Evolution submenu name in email-clients.txt	2015-07-24 15:05:57 +02:00
flexible-arrays.txt
futex-requeue-pi.txt
gcov.txt
gdb-kernel-debugging.txt
highuid.txt
HOWTO	docs: update HOWTO for 3.x -> 4.x versioning	2015-08-24 11:28:17 -06:00
hsi.txt
hw_random.txt
hwspinlock.txt
init.txt
initrd.txt
intel_txt.txt
Intel-IOMMU.txt	x86/vt-d: Fix documentation of DRHD	2015-08-25 10:44:49 +02:00
io_ordering.txt
io-mapping.txt
iostats.txt
IPMI.txt
IRQ-affinity.txt
IRQ-domain.txt
IRQ.txt
irqflags-tracing.txt
isapnp.txt
java.txt
kasan.txt	Merge branch 'doc/4.2' into docs-next	2015-06-08 17:04:11 -06:00
kernel-doc-nano-HOWTO.txt	Documenation: Update location of docproc.c	2015-07-14 12:36:39 -06:00
kernel-docs.txt
kernel-parameters.txt	xen: features and fixes for 4.3-rc0	2015-09-08 11:46:48 -07:00
kernel-per-CPU-kthreads.txt
kmemcheck.txt
kmemleak.txt	Doc: Change wikipedia's URL from http to https	2015-06-22 10:14:05 -06:00
kobject.txt
kprobes.txt
kref.txt
kselftest.txt
ldm.txt
local_ops.txt
lockup-watchdogs.txt	watchdog: add watchdog_cpumask sysctl to assist nohz	2015-06-24 17:49:40 -07:00
logo.gif
logo.txt
lzo.txt
magic-number.txt
mailbox.txt	Documentation: minor typo fix in mailbox.txt	2015-08-13 18:03:18 -06:00
Makefile
ManagementStyle
md-cluster.txt	md-cluster: fix deadlock issue on message lock	2015-08-31 19:41:41 +02:00
md.txt	doc:md: fix typo in md.txt.	2015-06-23 06:49:44 -06:00
media-framework.txt
memory-barriers.txt	Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2015-09-03 15:46:07 -07:00
memory-hotplug.txt
men-chameleon-bus.txt	Documentation: Minor changes to men-chameleon-bus.txt	2015-07-24 15:15:17 +02:00
module-signing.txt	Move certificate handling to its own directory	2015-08-14 16:06:13 +01:00
mono.txt
nommu-mmap.txt
ntb.txt	NTB: Rename Intel code names to platform names	2015-07-04 14:09:25 -04:00
numastat.txt
oops-tracing.txt
padata.txt
parport-lowlevel.txt
parport.txt
percpu-rw-semaphore.txt
phy.txt
pi-futex.txt
pinctrl.txt
pnp.txt
preempt-locking.txt
printk-formats.txt
pwm.txt
ramoops.txt
rbtree.txt
remoteproc.txt	remoteproc: introduce rproc_get_by_phandle API	2015-06-16 21:12:52 +03:00
rfkill.txt
robust-futex-ABI.txt
robust-futexes.txt
rpmsg.txt
rtc.txt
SAK.txt
SecurityBugs
serial-console.txt
sgi-ioc4.txt
SM501.txt
smsc_ece1099.txt
sparse.txt
stable_api_nonsense.txt
stable_kernel_rules.txt
static-keys.txt	locking/static_keys: Fix up the static keys documentation	2015-09-15 07:12:06 +02:00
SubmitChecklist
SubmittingDrivers
SubmittingPatches	Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial	2015-09-01 18:46:42 -07:00
svga.txt
sysfs-rules.txt
sysrq.txt	mm, oom: do not panic for oom kills triggered from sysrq	2015-09-08 15:35:28 -07:00
this_cpu_ops.txt
unaligned-memory-access.txt
unicode.txt
unshare.txt
vfio.txt	vfio: powerpc/spapr: Support Dynamic DMA windows	2015-06-11 15:16:55 +10:00
VGA-softcursor.txt
vgaarbiter.txt
video-output.txt
vme_api.txt	Documentation: mention vme_master_mmap() in VME API	2015-06-12 17:26:56 -07:00
volatile-considered-harmful.txt
workqueue.txt
xillybus.txt
xz.txt
zorro.txt