On Tuesday, July 17, 2012, Tejun Heo wrote: > Currently, workqueue destroys all workers for offline CPUs unless > there are lingering work items. On some platforms, CPU hotplugs are > used as part of runtime powersaving and thus can be very frequent. > The overhead of destroying and re-creating workers on each cycle can > be noticeable. > > In addition, being different from the usual mode of opration, > kill-all-idle involves separate driving logic, which currently is > implemented across trustee_thread() and CPU hotplug notifier. This is > rather complex and ugly. > > This patchset updates workqueue CPU hotplug path such that a > disassociated global_cwq (the per-cpu worker pool) is run as if it's > running as an unbound one (WQ_UNBOUND) - executing work items ASAP > without concurrency management while following the usual worker > management based on idle timer. > > While this makes rebinding somewhat more complicated, as it has to be > able to rebind idle workers too, it allows overall hotplug path to be > much simpler. A disassociating global_cwq simply becomes an unbound > one at the end of CPU_DOWN_PREPARE and makes use of the same logic > already existing for WQ_UNBOUND. While re-associating, it switches > back to a bound one. Except during the transitions themselves, the > usual worker management is always in effect making trustee > unnecessary. > > 0001-workqueue-perform-cpu-down-operations-from-low-prior.patch > 0002-workqueue-drop-CPU_DYING-notifier-operation.patch > 0003-workqueue-ROGUE-workers-are-UNBOUND-workers.patch > 0004-workqueue-use-mutex-for-global_cwq-manager-exclusion.patch > 0005-workqueue-drop-bind-from-create_worker.patch > 0006-workqueue-reimplement-CPU-online-rebinding-to-handle.patch > 0007-workqueue-don-t-butcher-idle-workers-on-an-offline-C.patch > 0008-workqueue-remove-CPU-offline-trustee.patch > 0009-workqueue-simplify-CPU-hotplug-code.patch > > 0001 is fix for an unlikely race condition. 0002-0005 prepare for CPU > hotplug reimplementation. 0006 reimplements re-binding such that it > can handle idle workers too. 0007 drops killing idle workers of > offline CPUs. 0008 replaces trustee with the usual management logic. > 0009 refactors hotplug path a bit to clean it up. > > This patchset is on top of "workqueue: reimplement high priority using > a separate worker pool" patchset[1] and available on the following git > branch. > > git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git review-wq-hotplug > > include/linux/cpu.h | 5 > kernel/workqueue.c | 738 > ++++++++++++++++++++-------------------------------- > 2 files changed, 296 insertions(+), 447 deletions(-)
I like these changes. I suppose you're going to push them through your tree, right? I that case please free to add my Acked-by to them. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
