tcp: use RFC6298 compliant TCP RTO calculation #3
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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.
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/
Signed-off-by: Daniel Metz <[email protected]>
hgn
pushed a commit
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Jun 14, 2016
…offline_kmem()
memcg_offline_kmem() may be called from memcg_free_kmem() after a css
init failure. memcg_free_kmem() is a ->css_free callback which is
called without cgroup_mutex and memcg_offline_kmem() ends up using
css_for_each_descendant_pre() without any locking. Fix it by adding rcu
read locking around it.
mkdir: cannot create directory `65530': No space left on device
===============================
[ INFO: suspicious RCU usage. ]
4.6.0-work+ torvalds#321 Not tainted
-------------------------------
kernel/cgroup.c:4008 cgroup_mutex or RCU read lock required!
[ 527.243970] other info that might help us debug this:
[ 527.244715]
rcu_scheduler_active = 1, debug_locks = 0
2 locks held by kworker/0:5/1664:
#0: ("cgroup_destroy"){.+.+..}, at: [<ffffffff81060ab5>] process_one_work+0x165/0x4a0
#1: ((&css->destroy_work)#3){+.+...}, at: [<ffffffff81060ab5>] process_one_work+0x165/0x4a0
[ 527.248098] stack backtrace:
CPU: 0 PID: 1664 Comm: kworker/0:5 Not tainted 4.6.0-work+ torvalds#321
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
Workqueue: cgroup_destroy css_free_work_fn
Call Trace:
dump_stack+0x68/0xa1
lockdep_rcu_suspicious+0xd7/0x110
css_next_descendant_pre+0x7d/0xb0
memcg_offline_kmem.part.44+0x4a/0xc0
mem_cgroup_css_free+0x1ec/0x200
css_free_work_fn+0x49/0x5e0
process_one_work+0x1c5/0x4a0
worker_thread+0x49/0x490
kthread+0xea/0x100
ret_from_fork+0x1f/0x40
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Tejun Heo <[email protected]>
Acked-by: Vladimir Davydov <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: <[email protected]> [4.5+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
hgn
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Jan 29, 2020
With zpci_disable() working, lockdep detected a potential deadlock (lockdep output at the end). The deadlock is between recovering a PCI function via the /sys/bus/pci/devices/<dev>/recover attribute vs powering it off via /sys/bus/pci/slots/<slot>/power. The fix is analogous to the changes in commit 0ee223b ("scsi: core: Avoid that SCSI device removal through sysfs triggers a deadlock") that fixed a potential deadlock on removing a SCSI device via sysfs. [ 204.830107] ====================================================== [ 204.830109] WARNING: possible circular locking dependency detected [ 204.830111] 5.5.0-rc2-06072-gbc03ecc9a672 #6 Tainted: G W [ 204.830112] ------------------------------------------------------ [ 204.830113] bash/1034 is trying to acquire lock: [ 204.830115] 0000000192a1a610 (kn->count#200){++++}, at: kernfs_remove_by_name_ns+0x5c/0xa8 [ 204.830122] but task is already holding lock: [ 204.830123] 00000000c16134a8 (pci_rescan_remove_lock){+.+.}, at: pci_stop_and_remove_bus_device_locked+0x26/0x48 [ 204.830128] which lock already depends on the new lock. [ 204.830129] the existing dependency chain (in reverse order) is: [ 204.830130] -> #1 (pci_rescan_remove_lock){+.+.}: [ 204.830134] validate_chain+0x93a/0xd08 [ 204.830136] __lock_acquire+0x4ae/0x9d0 [ 204.830137] lock_acquire+0x114/0x280 [ 204.830140] __mutex_lock+0xa2/0x960 [ 204.830142] mutex_lock_nested+0x32/0x40 [ 204.830145] recover_store+0x4c/0xa8 [ 204.830147] kernfs_fop_write+0xe6/0x218 [ 204.830151] vfs_write+0xb0/0x1b8 [ 204.830152] ksys_write+0x6c/0xf8 [ 204.830154] system_call+0xd8/0x2d8 [ 204.830155] -> #0 (kn->count#200){++++}: [ 204.830187] check_noncircular+0x1e6/0x240 [ 204.830189] check_prev_add+0xfc/0xdb0 [ 204.830190] validate_chain+0x93a/0xd08 [ 204.830192] __lock_acquire+0x4ae/0x9d0 [ 204.830193] lock_acquire+0x114/0x280 [ 204.830194] __kernfs_remove.part.0+0x2e4/0x360 [ 204.830196] kernfs_remove_by_name_ns+0x5c/0xa8 [ 204.830198] remove_files.isra.0+0x4c/0x98 [ 204.830199] sysfs_remove_group+0x66/0xc8 [ 204.830201] sysfs_remove_groups+0x46/0x68 [ 204.830204] device_remove_attrs+0x52/0x90 [ 204.830207] device_del+0x182/0x418 [ 204.830208] pci_remove_bus_device+0x8a/0x130 [ 204.830210] pci_stop_and_remove_bus_device_locked+0x3a/0x48 [ 204.830212] disable_slot+0x68/0x100 [ 204.830213] power_write_file+0x7c/0x130 [ 204.830215] kernfs_fop_write+0xe6/0x218 [ 204.830217] vfs_write+0xb0/0x1b8 [ 204.830218] ksys_write+0x6c/0xf8 [ 204.830220] system_call+0xd8/0x2d8 [ 204.830221] other info that might help us debug this: [ 204.830223] Possible unsafe locking scenario: [ 204.830224] CPU0 CPU1 [ 204.830225] ---- ---- [ 204.830226] lock(pci_rescan_remove_lock); [ 204.830227] lock(kn->count#200); [ 204.830229] lock(pci_rescan_remove_lock); [ 204.830231] lock(kn->count#200); [ 204.830233] *** DEADLOCK *** [ 204.830234] 4 locks held by bash/1034: [ 204.830235] #0: 00000001b6fbc498 (sb_writers#4){.+.+}, at: vfs_write+0x158/0x1b8 [ 204.830239] #1: 000000018c9f5090 (&of->mutex){+.+.}, at: kernfs_fop_write+0xaa/0x218 [ 204.830242] #2: 00000001f7da0810 (kn->count#235){.+.+}, at: kernfs_fop_write+0xb6/0x218 [ 204.830245] #3: 00000000c16134a8 (pci_rescan_remove_lock){+.+.}, at: pci_stop_and_remove_bus_device_locked+0x26/0x48 [ 204.830248] stack backtrace: [ 204.830250] CPU: 2 PID: 1034 Comm: bash Tainted: G W 5.5.0-rc2-06072-gbc03ecc9a672 #6 [ 204.830252] Hardware name: IBM 8561 T01 703 (LPAR) [ 204.830253] Call Trace: [ 204.830257] [<00000000c05e10c0>] show_stack+0x88/0xf0 [ 204.830260] [<00000000c112dca4>] dump_stack+0xa4/0xe0 [ 204.830261] [<00000000c0694c06>] check_noncircular+0x1e6/0x240 [ 204.830263] [<00000000c0695bec>] check_prev_add+0xfc/0xdb0 [ 204.830264] [<00000000c06971da>] validate_chain+0x93a/0xd08 [ 204.830266] [<00000000c06994c6>] __lock_acquire+0x4ae/0x9d0 [ 204.830267] [<00000000c069867c>] lock_acquire+0x114/0x280 [ 204.830269] [<00000000c09ca15c>] __kernfs_remove.part.0+0x2e4/0x360 [ 204.830270] [<00000000c09cb5c4>] kernfs_remove_by_name_ns+0x5c/0xa8 [ 204.830272] [<00000000c09cee14>] remove_files.isra.0+0x4c/0x98 [ 204.830274] [<00000000c09cf2ae>] sysfs_remove_group+0x66/0xc8 [ 204.830276] [<00000000c09cf356>] sysfs_remove_groups+0x46/0x68 [ 204.830278] [<00000000c0e3dfe2>] device_remove_attrs+0x52/0x90 [ 204.830280] [<00000000c0e40382>] device_del+0x182/0x418 [ 204.830281] [<00000000c0dcfd7a>] pci_remove_bus_device+0x8a/0x130 [ 204.830283] [<00000000c0dcfe92>] pci_stop_and_remove_bus_device_locked+0x3a/0x48 [ 204.830285] [<00000000c0de7190>] disable_slot+0x68/0x100 [ 204.830286] [<00000000c0de6514>] power_write_file+0x7c/0x130 [ 204.830288] [<00000000c09cc846>] kernfs_fop_write+0xe6/0x218 [ 204.830290] [<00000000c08f3480>] vfs_write+0xb0/0x1b8 [ 204.830291] [<00000000c08f378c>] ksys_write+0x6c/0xf8 [ 204.830293] [<00000000c1154374>] system_call+0xd8/0x2d8 [ 204.830294] INFO: lockdep is turned off. Signed-off-by: Niklas Schnelle <[email protected]> Reviewed-by: Peter Oberparleiter <[email protected]> Signed-off-by: Vasily Gorbik <[email protected]>
hgn
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Jan 29, 2020
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 <[email protected]> Cc: Brian Masney <[email protected]> Cc: Lina Iyer <[email protected]> Cc: Maulik Shah <[email protected]> Signed-off-by: Stephen Boyd <[email protected]> Link: https://lore.kernel.org/r/[email protected] Reviewed-by: Bjorn Andersson <[email protected]> Signed-off-by: Linus Walleij <[email protected]>
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We need to initialise the struct ourselves, else we expose tcp-specific callbacks such as tcp_splice_read which will then trigger splat because the socket is an mptcp one: BUG: KASAN: slab-out-of-bounds in tcp_mstamp_refresh+0x80/0xa0 net/ipv4/tcp_output.c:57 Write of size 8 at addr ffff888116aa21d0 by task syz-executor.0/5478 CPU: 1 PID: 5478 Comm: syz-executor.0 Not tainted 5.5.0-rc6 #3 Call Trace: tcp_mstamp_refresh+0x80/0xa0 net/ipv4/tcp_output.c:57 tcp_rcv_space_adjust+0x72/0x7f0 net/ipv4/tcp_input.c:612 tcp_read_sock+0x622/0x990 net/ipv4/tcp.c:1674 tcp_splice_read+0x20b/0xb40 net/ipv4/tcp.c:791 do_splice+0x1259/0x1560 fs/splice.c:1205 To prevent build error with ipv6, add the recv/sendmsg function declaration to ipv6.h. The functions are already accessible "thanks" to retpoline related work, but they are currently only made visible by socket.c specific INDIRECT_CALLABLE macros. Reported-by: Christoph Paasch <[email protected]> Signed-off-by: Florian Westphal <[email protected]> Signed-off-by: Mat Martineau <[email protected]> Signed-off-by: David S. Miller <[email protected]>
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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 <[email protected]>
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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.
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
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/
Signed-off-by: Daniel Metz [email protected]