Ubuntu
linux package

lowlatency kernel is lacking support for latencytop

Bug #1655986 reported by Mikko Rantalainen on 2017-01-12

6

This bug affects 1 person

Affects		Status	Importance	Assigned to	Milestone
	linux (Ubuntu)	Fix Released	Undecided	Tim Gardner
	Zesty	Fix Released	Undecided	Tim Gardner

Bug Description

Actual behavior:

$ sudo latencytop
mount: none is already mounted or /sys/kernel/debug busy
Please enable the CONFIG_LATENCYTOP configuration in your kernel.
Exiting...

$ grep -i latencytop /boot/config-`uname -r`
CONFIG_HAVE_LATENCYTOP_SUPPORT=y
# CONFIG_LATENCYTOP is not set

Expected behavior:

# working latencytop and
$ grep -i latencytop /boot/config-`uname -r`
CONFIG_HAVE_LATENCYTOP_SUPPORT=y
CONFIG_LATENCYTOP=y

Tested with package linux-image-4.4.0-57-lowlatency.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-lowlatency 4.4.0.59.62
ProcVersionSignature: Ubuntu 4.4.0-57.78-lowlatency 4.4.35
Uname: Linux 4.4.0-57-lowlatency x86_64
ApportVersion: 2.20.1-0ubuntu2.4
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: mira 2801 F.... pulseaudio
CurrentDesktop: MATE
Date: Thu Jan 12 16:33:59 2017
EcryptfsInUse: Yes
HibernationDevice:
#RESUME=UUID=609d4e01-862b-4199-bd45-ad8841f8c8c3
#RESUME=UUID=69fefec2-0a4f-489b-bb6e-62eab3d97735
InstallationDate: Installed on 2009-10-08 (2652 days ago)
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Alpha amd64 (20091008)
IwConfig:
lo no wireless extensions.

eth1 no wireless extensions.
MachineType: System manufacturer System Product Name
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-57-lowlatency root=UUID=23b87e6c-20b4-4242-9489-1599d62abcce ro vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-4.4.0-57-lowlatency N/A
linux-backports-modules-4.4.0-57-lowlatency N/A
linux-firmware 1.157.6
RfKill:

SourcePackage: linux
UpgradeStatus: Upgraded to xenial on 2016-11-14 (59 days ago)
dmi.bios.date: 08/20/2013
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 1401
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: P8H77-M PRO
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: Rev X.0x
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr1401:bd08/20/2013:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKCOMPUTERINC.:rnP8H77-MPRO:rvrRevX.0x:cvnChassisManufacture:ct3:cvrChassisVersion:
dmi.product.name: System Product Name
dmi.product.version: System Version
dmi.sys.vendor: System manufacturer

Tags:

CVE References

2017-2636

Revision history for this message

Mikko Rantalainen (mira) wrote on 2017-01-12:

#1

AlsaInfo.txt Edit (46.3 KiB, text/plain; charset="utf-8")
CRDA.txt Edit (422 bytes, text/plain; charset="utf-8")
CurrentDmesg.txt Edit (100.2 KiB, text/plain; charset="utf-8")
Dependencies.txt Edit (3.5 KiB, text/plain; charset="utf-8")
JournalErrors.txt Edit (62.3 KiB, text/plain; charset="utf-8")
Lspci.txt Edit (9.3 KiB, text/plain; charset="utf-8")
Lsusb.txt Edit (593 bytes, text/plain; charset="utf-8")
ProcCpuinfo.txt Edit (3.7 KiB, text/plain; charset="utf-8")
ProcEnviron.txt Edit (102 bytes, text/plain; charset="utf-8")
ProcInterrupts.txt Edit (2.2 KiB, text/plain; charset="utf-8")
ProcModules.txt Edit (4.7 KiB, text/plain; charset="utf-8")
PulseList.txt Edit (19.2 KiB, text/plain; charset="utf-8")
UdevDb.txt Edit (161.9 KiB, text/plain; charset="utf-8")
WifiSyslog.txt Edit (181.8 KiB, text/plain; charset="utf-8")

Revision history for this message

Brad Figg (brad-figg) wrote on 2017-01-12: Status changed to Confirmed

#2

This change was made by a bot.

Changed in linux (Ubuntu):
status:	New → Confirmed

Revision history for this message

Tim Gardner (timg-tpi) wrote on 2017-01-12:

#3

We discussed this feature in July 2014 and decided then to disable it. Unless there have been significant changes to the implementation I see no reason to reverse our decision.

https://lists.ubuntu.com/archives/kernel-team/2014-July/045006.html

Changed in linux (Ubuntu):
status:	Confirmed → Won't Fix

Revision history for this message

Mikko Rantalainen (mira) wrote on 2017-03-08:

#4

I think that *-lowlatency-* kernels should include CONFIG_LATENCYTOP by default. I agree that *-generic-* kernels do not need that. If administrator has installed lowlatency kernel they clearly are interested in lowest possible latency and Ubuntu should provide tools to figure out where the current bottlenecks are.

Does popcon support querying for combination of lowlatency kernel AND latencytop? Also note that since the CONFIG_LATENCYTOP was dropped, latencytop is practically broken and cannot be used for anything, which could explain its low usage.

(I also wonder if the increased RAM usage is *really* a big deal for desktop class machines. Sure, CONFIG_LATENCYTOP may increase RAM usage by 3848 bytes per task but for busy desktop or workstation running around 1000 tasks that will result in increase of less than 4 *MB*. If you're running 1000 tasks today, you probably have at least 4 *GB* of RAM so the difference is less than 0.1%.)

Revision history for this message

Colin Ian King (colin-king) wrote on 2017-03-08:

#5

Sounds like a sound justification to have this enabled to me. Most machines can enough memory to support this per-process overhead.

Revision history for this message

Tim Gardner (timg-tpi) wrote on 2017-03-08:

#6

UBUNTU: [Config] CONFIG_LATENCYTOP=y for amd64 lowlatency

Changed in linux (Ubuntu Zesty):
assignee:	nobody → Tim Gardner (timg-tpi)
status:	Won't Fix → Fix Committed

Revision history for this message

Launchpad Janitor (janitor) wrote on 2017-03-16:

#7

This bug was fixed in the package linux - 4.10.0-13.15

---------------
linux (4.10.0-13.15) zesty; urgency=low

[ Tim Gardner ]

* Release Tracking Bug
- LP: #1671614

* ehci-platform needed in usb-modules udeb (LP: #1671589)
- d-i: add ehci-platform to usb-modules

  * irqchip/gic-v3-its: Enable cacheable attribute Read-allocate hints
    (LP: #1671598)
    - irqchip/gic-v3-its: Enable cacheable attribute Read-allocate hints

  * iommu: Fix static checker warning in iommu_insert_device_resv_regions
    (LP: #1671599)
    - iommu: Fix static checker warning in iommu_insert_device_resv_regions

* QDF2400: Fix panic introduced by erratum 1003 (LP: #1671602)
- arm64: Avoid clobbering mm in erratum workaround on QDF2400

* QDF2400 PCI ports require ACS quirk (LP: #1671601)
- PCI: Add ACS quirk for Qualcomm QDF2400 and QDF2432

* tty: pl011: Work around QDF2400 E44 stuck BUSY bit (LP: #1671600)
- tty: pl011: Work around QDF2400 E44 stuck BUSY bit

* CVE-2017-2636
- tty: n_hdlc: get rid of racy n_hdlc.tbuf

* Sync virtualbox to 5.1.16-dfsg-1 in zesty (LP: #1671470)
- ubuntu: vbox -- Update to 5.1.16-dfsg-1

-- Tim Gardner <email address hidden> Thu, 09 Mar 2017 06:16:24 -0700

Changed in linux (Ubuntu Zesty):
status:	Fix Committed → Fix Released

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