linux-kernel - [PATCH 0/6 v3] sched/mm: LRU drain flush on nohz

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Message-ID: <20250410152327.24504-1-frederic@kernel.org>
Date: Thu, 10 Apr 2025 17:23:21 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Frederic Weisbecker <frederic@...nel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Valentin Schneider <vschneid@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Michal Hocko <mhocko@...nel.org>,
	linux-mm@...ck.org,
	Ingo Molnar <mingo@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 0/6 v3] sched/mm: LRU drain flush on nohz_full

Hi,

When LRUs are pending, the drain can be triggered remotely, whether the
remote CPU is running in userspace in nohz_full mode or not. This kind
of noise is expected to be caused by preparatory work before a task
runs isolated in userspace. This patchset is a proposal to flush that
before the task starts its critical work in userspace.

Changes since v2:

* Add tags (thanks everyone)
* Assume TASK_WORK_DEQUEUED is set before calling task_work_add() (Oleg)
* Return -EINVAL if queued from kthread instead of silently ignoring.
* Queue from a more appropriate place (folio_batch_add()) (Michal)
* Refactor changelog on last patch (Michal)

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
	task/work

HEAD: 036bfe5153de18c995653ee5074d5eec463bbde0

Thanks,
	Frederic
---

Frederic Weisbecker (6):
      task_work: Provide means to check if a work is queued
      sched/fair: Use task_work_queued() on numa_work
      sched: Use task_work_queued() on cid_work
      tick/nohz: Move nohz_full related fields out of hot task struct's places
      sched/isolation: Introduce isolated task work
      mm: Drain LRUs upon resume to userspace on nohz_full CPUs


 include/linux/pagevec.h         | 18 ++----------------
 include/linux/sched.h           | 15 +++++++++------
 include/linux/sched/isolation.h | 17 +++++++++++++++++
 include/linux/swap.h            |  1 +
 include/linux/task_work.h       | 12 ++++++++++++
 kernel/sched/core.c             |  6 ++----
 kernel/sched/fair.c             |  5 +----
 kernel/sched/isolation.c        | 34 ++++++++++++++++++++++++++++++++++
 kernel/sched/sched.h            |  1 +
 kernel/task_work.c              |  9 +++++++--
 mm/swap.c                       | 30 +++++++++++++++++++++++++++++-
 11 files changed, 115 insertions(+), 33 deletions(-)