** Package changed: ubuntu => linux (Ubuntu) -- 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/1315619
Title: Job with 4 threads not assigned 4 distinct cores Status in “linux” package in Ubuntu: New Bug description: On 12.04, I have reliably found that a job which starts 4 long-running threads on an otherwise-idle machine (there are some other threads which have been running for some time, but they have been kill -STOPped) gets the threads allocated to 4 distinct cores on my Haswell. On 14.04, I found that the threads were allocated to cores 0, 1, 5, 6 - that is, two were running on the two hyper-threads 1 and 5 of the same core, and performance was 30% less than expected. I can get around this with explicit taskset commands, but for my use case it's a serious regression from 12.04. I am not willing to disable hyperthreading, because it gives a large performance boost on other things I do on the same machine. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1315619/+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
