lkml.org 
[lkml]   [2014]   [Jul]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Subject[PATCH v2 0/5] sched: Add on_rq states and remove several double rq locks
From
Date
This series aims to get rid of some places where locks of two RQs are held
at the same time.

Patch [1/5] is a preparation/cleanup. It replaces old (.on_rq == 1) with new
(.on_rq == ONRQ_QUEUED) everywhere. No functional changes.

Patch [2/5] is main in the series. It introduces new state: ONRQ_MIGRATING
and teaches scheduler to understand it (we need a little changes predominantly
in try_to_wake_up()). This will be used in the following way:

(we are changing task's rq)

raw_spin_lock(&src_rq->lock);
dequeue_task(src_rq, p, 0);
p->on_rq = ONRQ_MIGRATING;
set_task_cpu(p, dst_cpu);
raw_spin_unlock(&src_rq->lock);

raw_spin_lock(&dst_rq->lock);
p->on_rq = ONRQ_QUEUED;
enqueue_task(dst_rq, p, 0);
raw_spin_unlock(&dst_rq->lock);

Patches [3-5/5] remove double locks and use new ONRQ_MIGRATING state.
They allow unlocked using of 3-4 function, which looks safe for me.

The series doesn't add any overhead, and it shouldn't worsen performance,
I think. It improves granularity, and it's possible to imagine situations,
which will be happier without double rq lock.

v2: Changes in [2/5] and [5/5].

---

Kirill Tkhai (5):
sched: Wrapper for checking task_struct's .on_rq
sched: Teach scheduler to understand ONRQ_MIGRATING state
sched: Remove double_rq_lock() from __migrate_task()
sched/fair: Remove double_lock_balance() from active_load_balance_cpu_stop()
sched/fair: Remove double_lock_balance() from load_balance()


kernel/sched/core.c | 123 +++++++++++++++++++++++--------------
kernel/sched/deadline.c | 14 ++--
kernel/sched/fair.c | 155 ++++++++++++++++++++++++++++++----------------
kernel/sched/rt.c | 16 ++---
kernel/sched/sched.h | 13 ++++
kernel/sched/stop_task.c | 2 -
6 files changed, 206 insertions(+), 117 deletions(-)

--
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>


\
 
 \ /
  Last update: 2014-07-26 17:41    [W:0.108 / U:0.080 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site