Stable Release Update Justification: Impact of bug: On low load systems with specific work load characteristics the load average may not be representative of the real load. Given a specific test case it is possible to load a system with NR_CPUS number of tasks and yet have a load avg of 0.00, though this is unlikely to occur in real work loads.
How addressed: The attached patch reworks the load accounting mechanism in the kernel scheduler. It ensures that the accounting is strictly dependent on the time (i.e. snapshot taken every 5 seconds) and the number of runnable and uninterruptible tasks at that given time. Previously, the accounting also depended on whether a cpu goes idle shortly after the 5 second snapshot. Reproduction: See attached reproduction test case. Run it once on a non- loaded system (boot to rescue mode works well). Top will report the cpu usage at 90%, but uptime will report a load avg near 0.00 instead of at least 0.90 as expected. Regression potential: The patch has been received well from senior Ubuntu kernel team members and some of the upstream kernel maintainers on lkml. For this reason it is assumed to be a good fix for this issue. The only code path touched by this patch involves the load avg accounting, so potential regressions could include incorrect load avg and/or some unforeseen general bug like a null dereference. However, the likelihood of either is minimal due to proper and thorough patch review. -- [karmic] CPU load not being reported accurately https://bugs.launchpad.net/bugs/513848 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
