Hello, Posting v4 (no new ideas for now). Patch 5 just for debugging, do not apply if not needed. This patchset implements stats estimation in kthread context. Simple tests do not show any problem. If testing, check that calculated chain_max_len does not deviates much. Overview of the basic concepts. More in the commit messages... RCU Locking: - 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. For now we apply a rlimit as max kthreads to create. - 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. - the allocated kthread context may grow from 1 to 50 allocated structures for ticks which saves memory for setups with small number of estimators - a task and its structure may be released if all estimators are unlinked from its chains, leaving the slot in the array empty - every kthread data structure allows limited number of estimators. Kthread 0 is also used to initially calculate the number of estimators to allow in every chain considering a sub-100 microsecond cond_resched rate. This number can be from 1 to hundreds. - kthread 0 has an additional job of optimizing the adding of estimators: they are first added in temp list (est_temp_list) and later kthread 0 distributes them to other kthreads. The optimization is based on the fact that newly added estimator should be estimated after 2 seconds, so we have the time to offload the adding to chain from controlling process to kthread 0. - to add new estimators we use the last added kthread context (est_add_ktid). The new estimators are linked to the chains 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. There are things that I don't like but for now I don't have a better idea for them: - calculation of chain_max_len can go wrong, depending on the current load, CPU speed, memory speeds, running in VM, whether tested estimators are in CPU cache, even if we are doing it in SCHED_FIFO mode. I expect such noise to be insignificant but who knows. - ip_vs_stop_estimator is not a simple unlinking of list node, we spend cycles to account for the removed estimator - __ip_vs_mutex is global mutex for all netns. But it protects hash tables that are still global ones. Changes in v4: Patch 2: * kthread 0 can start with calculation phase in SCHED_FIFO mode to determine chain_max_len suitable for 100us cond_resched rate and 12% of 40ms CPU usage in a tick. Current value of IPVS_EST_TICK_CHAINS=48 determines tick time of 4.8ms (i.e. in units of 100us) which is 12% of max tick time of 40ms. The question is how reliable will be such calculation test. * est_calc_phase indicates a mode where we dequeue estimators from kthreads, apply new chain_max_len and enqueue again all estimators to kthreads, done by kthread 0 * est->ktid now can be -1 to indicate est is in est_temp_list ready to be distributed to kthread by kt 0, done in ip_vs_est_drain_temp_list(). kthread 0 data is now released only after the data for others kthreads * ip_vs_start_estimator was not setting ret = 0 * READ_ONCE not needed for volatile jiffies Patch 3: * restrict cpulist based on the cpus_allowed of process that assigns cpulist, not on cpu_possible_mask * change of cpulist will trigger calc phase Patch 5: * print message every minute, not 2 seconds Changes in v3: Patch 2: * calculate chain_max_len (was IPVS_EST_CHAIN_DEPTH) but it needs further tuning based on real estimation test * est_max_threads set from rlimit(RLIMIT_NPROC). I don't see analog to get_ucounts_value() to get the max value. * the atomic bitop for td->present is not needed, remove it * start filling based on est_row after 2 ticks are fully allocated. As 2/50 is 4% this can be increased more. Changes in v2: Patch 2: * kd->mutex is gone, cond_resched rate determined by IPVS_EST_CHAIN_DEPTH * IPVS_EST_MAX_COUNT is a hard limit now * kthread data is now 1-50 allocated tick structures, each containing heads for limited chains. Bitmaps should allow faster access. We avoid large allocations for structs. * as the td->present bitmap is shared, use atomic bitops * ip_vs_start_estimator now returns error code * _bh locking removed from stats->lock * bump arg is gone from ip_vs_est_reload_start * prepare for upcoming changes that remove _irq from u64_stats_fetch_begin_irq/u64_stats_fetch_retry_irq * est_add_ktid is now always valid Patch 3: * use .. in est_nice docs Julian Anastasov (5): 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 ipvs: debug the tick time Documentation/networking/ipvs-sysctl.rst | 24 +- include/net/ip_vs.h | 133 +++- net/netfilter/ipvs/ip_vs_core.c | 10 +- net/netfilter/ipvs/ip_vs_ctl.c | 371 ++++++++-- net/netfilter/ipvs/ip_vs_est.c | 895 +++++++++++++++++++++-- 5 files changed, 1301 insertions(+), 132 deletions(-) -- 2.37.3
