[PATCH 0/6] mm: Remote LRU per-cpu pagevec cache/per-cpu page list drain support

[Nicolas Saenz Julienne]

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(-)

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2.31.1