Hello, This patchset implements stats estimation in kthread context. Simple tests do not show any problem. Please review, comment, test, etc. Overview of the basic concepts. More in the commit messages... RCU Locking: - when RCU preemption is enabled the kthreads use just RCU lock for walking the chains and we do not need to reschedule. May be this is the common case for distribution kernels. In this case ip_vs_stop_estimator() is completely lockless. - when RCU preemption is not enabled, we reschedule by using refcnt for every estimator to track if the currently removed estimator is used at the same time by kthread for estimation. As RCU lock is unlocked during rescheduling, the deletion should wait kd->mutex, so that a new RCU lock is applied before the estimator is freed with RCU callback. - As stats are now RCU-locked, tot_stats, svc and dest which hold estimator structures are now always freed from RCU callback. This ensures RCU grace period after the ip_vs_stop_estimator() call. Kthread data: - every kthread works over its own data structure and all such structures are attached to array - even while there can be a kthread structure, its task may not be running, eg. before first service is added or while the sysctl var is set to an empty cpulist or when run_estimation is 0. - a task and its structure may be released if all estimators are unlinked from its chains, leaving the slot in the array empty - to add new estimators we use the last added kthread context (est_add_ktid). The new estimators are linked to the chain just before the estimated one, based on add_row. This ensures their estimation will start after 2 seconds. If estimators are added in bursts, common case if all services and dests are initially configured, we may spread the estimators to more chains. This will reduce the chain imbalance. - the chain imbalance is not so fatal when we use kthreads. We design each kthread for part of the possible CPU usage, so even if some chain exceeds its time slot it would happen all the time or sporadic depending on the scheduling but still keeping the 2-second interval. The cpulist isolation can make the things more stable as a 2-second time interval per estimator. Julian Anastasov (4): ipvs: add rcu protection to stats ipvs: use kthreads for stats estimation ipvs: add est_cpulist and est_nice sysctl vars ipvs: run_estimation should control the kthread tasks Documentation/networking/ipvs-sysctl.rst | 24 +- include/net/ip_vs.h | 144 +++++++- net/netfilter/ipvs/ip_vs_core.c | 10 +- net/netfilter/ipvs/ip_vs_ctl.c | 287 ++++++++++++++-- net/netfilter/ipvs/ip_vs_est.c | 408 +++++++++++++++++++---- 5 files changed, 771 insertions(+), 102 deletions(-) -- 2.37.2
