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Tcp rto rfc 6298 compliant #4

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Tcp rto rfc 6298 compliant #4

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danielmgit
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tcp: use RFC6298 compliant TCP RTO calculation

This patch adjusts Linux RTO calculation to be RFC6298 Standard
compliant. MinRTO is no longer added to the computed RTO, RTO damping
and overestimation are decreased.

In RFC 6298 Standard TCP Retransmission Timeout (RTO) calculation the
calculated RTO is rounded up to the Minimum RTO (MinRTO), if it is
less.  The Linux implementation as a discrepancy to the Standard
basically adds the defined MinRTO to the calculated RTO. When
comparing both approaches, the Linux calculation seems to perform
worse for sender limited TCP flows like Telnet, SSH or constant bit
rate encoded transmissions, especially for Round Trip Times (RTT) of
50ms to 800ms.

Compared to the Linux implementation the RFC 6298 proposed RTO
calculation performs better and more precise in adapting to current
network characteristics. Extensive measurements for bulk data did not
show a negative impact of the adjusted calculation.

Using the RFC 6298 compliant implementation, the tcp_sock struct variable
u32 mdev_max_us becomes obsolete and consequently is being removed.

Exemplary performance comparison for sender-limited-flows:

- Rate: 10Mbit/s
- Delay: 200ms, Delay Variation: 10ms
- Time between each scheduled segment: 1s
- Amount Data Segments: 300
- Mean of 11 runs

         Mean Response Waiting Time [milliseconds]

PER [%] |   0.5      1    1.5      2      3      5      7     10
--------+-------------------------------------------------------
old     | 206.4  208.6  218.0  218.6  227.2  249.3  274.7  308.2
new     | 203.9  206.0  207.0  209.9  217.3  225.6  238.7  259.1

Detailed analysis:

https://docs.google.com/document/d/1pKmPfnQb6fDK4qpiNVkN8cQyGE4wYDZukcuZfR-BnnM/

Reasoning for historic design:

Sarolahti, P.; Kuznetsov, A. (2002). Congestion Control in Linux TCP.
Conference Paper. Proceedings of the FREENIX Track. 2002 USENIX Annual
https://www.cs.helsinki.fi/research/iwtcp/papers/linuxtcp.pdf

Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: Daniel Metz <dmetz@mytum.de>

mlauss2 and others added 7 commits June 14, 2016 15:35
@mlauss2 @danielmgit
net: au1000_eth: fix PHY detection
00a8231 
Commit 7f85442
("phy: Add API for {un}registering an mdio device to a bus.")
broke PHY detection on this driver with a copy-paste bug:
The code is looking 32 times for a PHY at address 0.

Fixes ethernet on AMD DB1100/DB1500/DB1550 boards which have
their (autodetected) PHYs at address 31.

Cc: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
@davem330 @danielmgit
Revert "net: au1000_eth: fix PHY detection"
3ab51f9 
This reverts commit a2f2721.

I applied the wrong version of this.

Signed-off-by: David S. Miller <davem@davemloft.net>
@mlauss2 @danielmgit
net: au1000_eth: fix PHY detection
5b22d37 
Commit 7f85442
("phy: Add API for {un}registering an mdio device to a bus.")
broke PHY detection on this driver with a copy-paste bug:
The code is looking 32 times for a PHY at address 0.

Fixes ethernet on AMD DB1100/DB1500/DB1550 boards which have
their (autodetected) PHYs at address 31.

Cc: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
@davem330 @danielmgit
ipconfig: Protect ic_addrservaddr with IPCONFIG_DYNAMIC.
600a28b 
>> net/ipv4/ipconfig.c:130:15: warning: 'ic_addrservaddr' defined but not used [-Wunused-variable]
    static __be32 ic_addrservaddr = NONE; /* IP Address of the IP addresses'server */

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
@danielmgit
net_sched: prio: properly report out of memory errors
d8fafc0 
At Qdisc creation or change time, prio_tune() creates missing
pfifo qdiscs but does not return an error code if one
qdisc could not be allocated.

Leaving a qdisc in non operational state without telling user
anything about this problem is not good.

Also, testing if we replace something different than noop_qdisc
a second time makes no sense so I removed useless code.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
@ikhorn @danielmgit
net: ethernet: ti: cpsw: use destroy ctlr to destroy channels
f4bbb2c 
There is no reason to destroy channels that are destroyed while
cpdma_ctlr destroy. In this case no need to remember how much
channels where created and destroy them by one, as cpdma_ctlr
destroys all of them.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
@danielmgit
tcp: use RFC6298 compliant TCP RTO calculation
2ce8335 
This patch adjusts Linux RTO calculation to be RFC6298 Standard
compliant. MinRTO is no longer added to the computed RTO, RTO damping
and overestimation are decreased.

In RFC 6298 Standard TCP Retransmission Timeout (RTO) calculation the
calculated RTO is rounded up to the Minimum RTO (MinRTO), if it is
less.  The Linux implementation as a discrepancy to the Standard
basically adds the defined MinRTO to the calculated RTO. When
comparing both approaches, the Linux calculation seems to perform
worse for sender limited TCP flows like Telnet, SSH or constant bit
rate encoded transmissions, especially for Round Trip Times (RTT) of
50ms to 800ms.

Compared to the Linux implementation the RFC 6298 proposed RTO
calculation performs better and more precise in adapting to current
network characteristics. Extensive measurements for bulk data did not
show a negative impact of the adjusted calculation.

Using the RFC 6298 compliant implementation, the tcp_sock struct variable
u32 mdev_max_us becomes obsolete and consequently is being removed.

Exemplary performance comparison for sender-limited-flows:

- Rate: 10Mbit/s
- Delay: 200ms, Delay Variation: 10ms
- Time between each scheduled segment: 1s
- Amount Data Segments: 300
- Mean of 11 runs

         Mean Response Waiting Time [milliseconds]

PER [%] |   0.5      1    1.5      2      3      5      7     10
--------+-------------------------------------------------------
old     | 206.4  208.6  218.0  218.6  227.2  249.3  274.7  308.2
new     | 203.9  206.0  207.0  209.9  217.3  225.6  238.7  259.1

Detailed analysis:

https://docs.google.com/document/d/1pKmPfnQb6fDK4qpiNVkN8cQyGE4wYDZukcuZfR-BnnM/

Reasoning for historic design:

Sarolahti, P.; Kuznetsov, A. (2002). Congestion Control in Linux TCP.
Conference Paper. Proceedings of the FREENIX Track. 2002 USENIX Annual
https://www.cs.helsinki.fi/research/iwtcp/papers/linuxtcp.pdf

Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: Daniel Metz <dmetz@mytum.de>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
@danielmgit danielmgit closed this Jun 14, 2016
hgn pushed a commit that referenced this pull request Jan 29, 2020
@bebarino @linusw
pinctrl: qcom: Don't lock around irq_set_irq_wake()
1d44616 
We don't need to hold the local pinctrl lock here to set irq wake on the
summary irq line. Doing so only leads to lockdep warnings instead of
protecting us from anything. Remove the locking.

 WARNING: possible circular locking dependency detected
 5.4.11 #2 Tainted: G        W
 ------------------------------------------------------
 cat/3083 is trying to acquire lock:
 ffffff81f4fa58c0 (&irq_desc_lock_class){-.-.}, at: __irq_get_desc_lock+0x64/0x94

 but task is already holding lock:
 ffffff81f4880c18 (&pctrl->lock){-.-.}, at: msm_gpio_irq_set_wake+0x48/0x7c

 which lock already depends on the new lock.

 the existing dependency chain (in reverse order) is:

 -> #1 (&pctrl->lock){-.-.}:
        _raw_spin_lock_irqsave+0x64/0x80
        msm_gpio_irq_ack+0x68/0xf4
        __irq_do_set_handler+0xe0/0x180
        __irq_set_handler+0x60/0x9c
        irq_domain_set_info+0x90/0xb4
        gpiochip_hierarchy_irq_domain_alloc+0x110/0x200
        __irq_domain_alloc_irqs+0x130/0x29c
        irq_create_fwspec_mapping+0x1f0/0x300
        irq_create_of_mapping+0x70/0x98
        of_irq_get+0xa4/0xd4
        spi_drv_probe+0x4c/0xb0
        really_probe+0x138/0x3f0
        driver_probe_device+0x70/0x140
        __device_attach_driver+0x9c/0x110
        bus_for_each_drv+0x88/0xd0
        __device_attach+0xb0/0x160
        device_initial_probe+0x20/0x2c
        bus_probe_device+0x34/0x94
        device_add+0x35c/0x3f0
        spi_add_device+0xbc/0x194
        of_register_spi_devices+0x2c8/0x408
        spi_register_controller+0x57c/0x6fc
        spi_geni_probe+0x260/0x328
        platform_drv_probe+0x90/0xb0
        really_probe+0x138/0x3f0
        driver_probe_device+0x70/0x140
        device_driver_attach+0x4c/0x6c
        __driver_attach+0xcc/0x154
        bus_for_each_dev+0x84/0xcc
        driver_attach+0x2c/0x38
        bus_add_driver+0x108/0x1fc
        driver_register+0x64/0xf8
        __platform_driver_register+0x4c/0x58
        spi_geni_driver_init+0x1c/0x24
        do_one_initcall+0x1a4/0x3e8
        do_initcall_level+0xb4/0xcc
        do_basic_setup+0x30/0x48
        kernel_init_freeable+0x124/0x1a8
        kernel_init+0x14/0x100
        ret_from_fork+0x10/0x18

 -> #0 (&irq_desc_lock_class){-.-.}:
        __lock_acquire+0xeb4/0x2388
        lock_acquire+0x1cc/0x210
        _raw_spin_lock_irqsave+0x64/0x80
        __irq_get_desc_lock+0x64/0x94
        irq_set_irq_wake+0x40/0x144
        msm_gpio_irq_set_wake+0x5c/0x7c
        set_irq_wake_real+0x40/0x5c
        irq_set_irq_wake+0x70/0x144
        cros_ec_rtc_suspend+0x38/0x4c
        platform_pm_suspend+0x34/0x60
        dpm_run_callback+0x64/0xcc
        __device_suspend+0x310/0x41c
        dpm_suspend+0xf8/0x298
        dpm_suspend_start+0x84/0xb4
        suspend_devices_and_enter+0xbc/0x620
        pm_suspend+0x210/0x348
        state_store+0xb0/0x108
        kobj_attr_store+0x14/0x24
        sysfs_kf_write+0x4c/0x64
        kernfs_fop_write+0x15c/0x1fc
        __vfs_write+0x54/0x18c
        vfs_write+0xe4/0x1a4
        ksys_write+0x7c/0xe4
        __arm64_sys_write+0x20/0x2c
        el0_svc_common+0xa8/0x160
        el0_svc_handler+0x7c/0x98
        el0_svc+0x8/0xc

 other info that might help us debug this:

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&pctrl->lock);
                                lock(&irq_desc_lock_class);
                                lock(&pctrl->lock);
   lock(&irq_desc_lock_class);

  *** DEADLOCK ***

 7 locks held by cat/3083:
  #0: ffffff81f06d1420 (sb_writers#7){.+.+}, at: vfs_write+0xd0/0x1a4
  #1: ffffff81c8935680 (&of->mutex){+.+.}, at: kernfs_fop_write+0x12c/0x1fc
  #2: ffffff81f4c322f0 (kn->count#337){.+.+}, at: kernfs_fop_write+0x134/0x1fc
  #3: ffffffe89a641d60 (system_transition_mutex){+.+.}, at: pm_suspend+0x108/0x348
  #4: ffffff81f190e970 (&dev->mutex){....}, at: __device_suspend+0x168/0x41c
  #5: ffffff81f183d8c0 (lock_class){-.-.}, at: __irq_get_desc_lock+0x64/0x94
  #6: ffffff81f4880c18 (&pctrl->lock){-.-.}, at: msm_gpio_irq_set_wake+0x48/0x7c

 stack backtrace:
 CPU: 4 PID: 3083 Comm: cat Tainted: G        W         5.4.11 #2
 Hardware name: Google Cheza (rev3+) (DT)
 Call trace:
  dump_backtrace+0x0/0x174
  show_stack+0x20/0x2c
  dump_stack+0xc8/0x124
  print_circular_bug+0x2ac/0x2c4
  check_noncircular+0x1a0/0x1a8
  __lock_acquire+0xeb4/0x2388
  lock_acquire+0x1cc/0x210
  _raw_spin_lock_irqsave+0x64/0x80
  __irq_get_desc_lock+0x64/0x94
  irq_set_irq_wake+0x40/0x144
  msm_gpio_irq_set_wake+0x5c/0x7c
  set_irq_wake_real+0x40/0x5c
  irq_set_irq_wake+0x70/0x144
  cros_ec_rtc_suspend+0x38/0x4c
  platform_pm_suspend+0x34/0x60
  dpm_run_callback+0x64/0xcc
  __device_suspend+0x310/0x41c
  dpm_suspend+0xf8/0x298
  dpm_suspend_start+0x84/0xb4
  suspend_devices_and_enter+0xbc/0x620
  pm_suspend+0x210/0x348
  state_store+0xb0/0x108
  kobj_attr_store+0x14/0x24
  sysfs_kf_write+0x4c/0x64
  kernfs_fop_write+0x15c/0x1fc
  __vfs_write+0x54/0x18c
  vfs_write+0xe4/0x1a4
  ksys_write+0x7c/0xe4
  __arm64_sys_write+0x20/0x2c
  el0_svc_common+0xa8/0x160
  el0_svc_handler+0x7c/0x98
  el0_svc+0x8/0xc

Fixes: 6aced33 ("pinctrl: msm: drop wake_irqs bitmap")
Cc: Douglas Anderson <dianders@chromium.org>
Cc: Brian Masney <masneyb@onstation.org>
Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Maulik Shah <mkshah@codeaurora.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20200121180950.36959-1-swboyd@chromium.org
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
hgn pushed a commit that referenced this pull request Jan 29, 2020
@davem330
Merge branch 'mlxsw-Offload-TBF'
3333e50 
Ido Schimmel says:

====================
mlxsw: Offload TBF

Petr says:

In order to allow configuration of shapers on Spectrum family of
machines, recognize TBF either as root Qdisc, or as a child of ETS or
PRIO. Configure rate of maximum shaper according to TBF rate setting,
and maximum shaper burst size according to TBF burst setting.

- Patches #1 and #2 make the TBF shaper suitable for offloading.
- Patches #3, #4 and #5 are refactoring aimed at easier support of leaf
  Qdiscs in general.
- Patches #6 to torvalds#10 gradually introduce TBF offload.
- Patches torvalds#11 to torvalds#14 add selftests.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
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@danielmgit @mlauss2 @davem330 @ikhorn