This series introduces an alternative locking scheme around mm/swap.c's per-cpu LRU pagevec caches and mm/page_alloc.c's per-cpu page lists which will allow for remote CPUs to drain them. Currently, only a local CPU is permitted to change its per-cpu lists, and it's expected to do so, on-demand, whenever a process demands it (by means of queueing an drain task on the local CPU). Most systems will handle this promptly, but it'll cause problems for NOHZ_FULL CPUs that can't take any sort of interruption without breaking their functional guarantees (latency, bandwidth, etc...). Having a way for these processes to remotely drain the lists themselves will make co-existing with isolated CPUs possible, at the cost of more constraining locks. Fortunately for non-NOHZ_FULL users, the alternative locking scheme and remote drain code are conditional to a static key which is disabled by default. This guarantees minimal functional or performance regressions. The feature will only be enabled if NOHZ_FULL's initialization process was successful. This work is based on a previous series by Thomas Gleixner, Anna-Maria Gleixner, and Sebastian Andrzej Siewior[1]. [1] https://patchwork.kernel.org/project/linux-mm/patch/20190424111208.24459-3-bigeasy@xxxxxxxxxxxxx/ Nicolas Saenz Julienne (6): mm/swap: Introduce lru_cpu_needs_drain() mm/swap: Introduce alternative per-cpu LRU cache locking mm/swap: Allow remote LRU cache draining mm/page_alloc: Introduce alternative per-cpu list locking mm/page_alloc: Allow remote per-cpu page list draining sched/isolation: Enable 'remote_pcpu_cache_access' on NOHZ_FULL systems kernel/sched/isolation.c | 9 +- mm/internal.h | 2 + mm/page_alloc.c | 111 ++++++++++++++++----- mm/swap.c | 202 ++++++++++++++++++++++++++++++--------- 4 files changed, 253 insertions(+), 71 deletions(-) -- 2.31.1
