Currently the kernel doesn't handle cpusets properly during suspend/resume. After a resume, all non-root cpusets end up having only 1 cpu (the boot cpu), causing massive performance degradation of workloads. One major user of cpusets is libvirt, which means that after a suspend/hibernation cycle, all VMs suddenly end up running terribly slow! Also, the kernel moves the tasks from one cpuset to another during CPU hotplug in the suspend/resume path, leading to a task-management nightmare after resume. Patch 1 fixes this by keeping cpusets unmodified in the suspend/resume path. But to ensure we don't trip over, it keeps the sched domains updated during every CPU hotplug in the s/r path. This is a long standing issue and we need to fix up stable kernels too. The rest of the patches in the series are mostly cleanups/optimizations (except patch 4 which is a non-critical bug fix). -- Srivatsa S. Bhat (5): CPU hotplug, cpusets, suspend: Don't modify cpusets during suspend/resume cpusets, hotplug: Implement cpuset tree traversal in a helper function cpusets, hotplug: Restructure functions that are invoked during hotplug cpusets: Update tasks' cpus_allowed mask upon updates to root cpuset cpusets: Remove/update outdated comments include/linux/cpuset.h | 4 + kernel/cpuset.c | 161 +++++++++++++++++++++++++++++++++++------------- kernel/sched/core.c | 44 +++++++++++-- 3 files changed, 159 insertions(+), 50 deletions(-) Thanks, Srivatsa S. Bhat IBM Linux Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/