Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.3 kernel[0].
If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'. If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'. Once testing of the upstream kernel is complete, please mark this bug as "Confirmed". Thanks in advance. [0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.3-wily/ ** Changed in: linux (Ubuntu) Importance: Undecided => Medium -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1516565 Title: Strange kernel or scheduling problem Status in linux package in Ubuntu: Incomplete Bug description: I see a strange kernel or scheduler problem with Kubuntu 15.04 and 15.10. I have Intel 3960X cpu with 6 cores (Hyperthreading is disabled). The problem is that when I run many CPU intensive applications (using full CPU), I cannot fully use all the cores of CPU. I tried a very simple app, which only multiplies some integers infinitly to emulate only high cpu usage with out any disk bottleneck. when I run multiple copies of the app, sometimes the scheduler assign all of them to a single core! Sometimes "top" shows that all CPU intensive apps are using only 0% CPU even though one of the cores is 100% utilized and the apps are definitely working. Sometimes the apps cannot use the full CPU and the CPU usage of a single app oscillates between 0% to 100%. The problem becomes visible when there are 4 or more CPU intensive apps. When there are 6 apps, the mouse movement becomes sluggish and the system becomes very unresponsive even though the "top" shows that the CPUs are not fully used. I tried adding intel_pstate=disable in GRUB and setting scheduler to SCHED_ISO, but no effect. I tried different kernel versions previously installed. The current kernel 4.2.0 and the previous kernel 3.19.0 have this problem. Kernel version 3.11.0-19 worked without any problems. When I change a device driver( like the NVIDIA binary driver version), the problem is fixed until the next reboot. Probably changing a device driver is resetting the kernel and temporally fixing the problem. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1516565/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
