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

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Date:   Tue, 21 Sep 2021 18:13:18 +0200
From:   Nicolas Saenz Julienne <nsaenzju@...hat.com>
To:     akpm@...ux-foundation.org, frederic@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        tglx@...utronix.de, cl@...ux.com, peterz@...radead.org,
        juri.lelli@...hat.com, mingo@...hat.com, mtosatti@...hat.com,
        nilal@...hat.com, mgorman@...e.de, ppandit@...hat.com,
        williams@...hat.com, bigeasy@...utronix.de,
        anna-maria@...utronix.de, linux-rt-users@...r.kernel.org,
        Nicolas Saenz Julienne <nsaenzju@...hat.com>
Subject: [PATCH 0/6] mm: Remote LRU per-cpu pagevec cache/per-cpu page list drain support

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@linutronix.de/

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