ssh server extremly unresponsive
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux (Ubuntu) |
Invalid
|
Undecided
|
Unassigned |
Bug Description
I describe the issue in few steps below.
1.) I want to transfer files from machine A (with ubuntu 11.04, but this is not important) to machine B (ubuntu 10.10; this is important to say) using scp.
2.) Machine B is under constant computational load due to a user program (a simulation) such that most of its CPU power is consumed by the program but it uses less then half of total (12 GB) memory and there is not any significant usage of disk and no other application is running. (Even no user logged into a GNOME session.)
3.) I issue the command scp on machine A; I immediatelly get prompt to give password. However the transfer does not start immediatelly after that. I must wait for some time, say half a minute or even full minute or more (I have not measured it.) just to see the start of the tranfer.
Few additional remarks:
Until recently machine B had had installed ubuntu 10.04 (Lucid Lynx, 64-bit) and there was no such problem even at higher computational loads. Similarly there was no such problem even in more distant past when the machine was running under Linux Mint Helena (based upon Ubuntu 9.10).
The long delays when doing scp occur if machine B was not exposed to an scp or ssh demand for a longer period of time. (Typically I face the problem in the morning when.) If an scp transfer is finally accomplished then I can start a new one which already works without delay.
Machine B is equipped with an Intel i7 CPU, 12 GB of DDR3 and it is a quite powerful workstation. All cores of CPU are set to run at maximum frequency.
I attach a file with content shown by the program top. (Grabbed in situation when a user is logged into GNOME session.)
ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: openssh-server 1:5.5p1-4ubuntu5
ProcVersionSign
Uname: Linux 2.6.35-28-generic x86_64
Architecture: amd64
Date: Fri May 13 10:39:53 2011
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release amd64 (20101007)
ProcEnviron:
LANGUAGE=en_GB:en
PATH=(custom, user)
LANG=en_GB.utf8
SHELL=/bin/bash
SourcePackage: openssh
---
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
Card hw:0 'Intel'/'HDA Intel at 0xd7ff8000 irq 73'
Mixer name : 'Analog Devices AD1989B'
Components : 'HDA:11d4989b,
Controls : 48
Simple ctrls : 27
DistroRelease: Ubuntu 10.10
HibernationDevice: RESUME=
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release amd64 (20101007)
IwConfig:
lo no wireless extensions.
eth0 no wireless extensions.
eth1 no wireless extensions.
MachineType: System manufacturer System Product Name
Package: openssh
ProcCmdLine: BOOT_IMAGE=
ProcEnviron:
LANGUAGE=en_GB:en
PATH=(custom, user)
LANG=en_GB.utf8
SHELL=/bin/bash
ProcVersionSign
Regression: Yes
RelatedPackageV
Reproducible: Yes
RfKill:
Tags: maverick kernel-config regression-release needs-upstream-
Uname: Linux 2.6.35-30-generic x86_64
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare
WifiSyslog:
dmi.bios.date: 11/12/2009
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 0704
dmi.board.
dmi.board.name: P6T DELUXE V2
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: Rev 1.xx
dmi.chassis.
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.
dmi.modalias: dmi:bvnAmerican
dmi.product.name: System Product Name
dmi.product.
dmi.sys.vendor: System manufacturer
Changed in linux (Ubuntu): | |
status: | New → Confirmed |
Changed in openssh (Ubuntu): | |
importance: | Undecided → Medium |
Martin, first, thanks for taking the time to file this bug report and help us make Ubuntu better.
This sounds more like a bug in the kernel's scheduling than openssh itself, I suspect anything trying to get
scheduled would have problems competing. Opening task against the kernel as well.
If you renice "prog.X" with
sudo renice `pidof prog.X` 5
Does the effect go away, or at least reduce significantly?
Also once you've ssh'd to the machine, do other programs run sluggishly?
Marking openssh task incomplete pending response (If it does go away with renice, and/or all programs that need CPU are sluggish, then this is not an openssh problem IMO).