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BACKPORT: rcu: Shrinker for lazy rcu

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The shrinker is used to speed up the free'ing of memory potentially held
by RCU lazy callbacks. RCU kernel module test cases show this to be
effective. Test is introduced in a later patch.

[Joel: register_shrinker() argument list change.]

Bug: 258241771
Bug: 222463781
Test: CQ
Change-Id: I6a73a9dae79ff35feca37abe2663e55a0f46dda8
Signed-off-by: Vineeth Pillai <vineeth@bitbyteword.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
(cherry picked from commit c945b4da7a)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/4318046
Tested-by: Joel Fernandes <joelaf@google.com>
Reviewed-by: Vineeth Pillai <vineethrp@google.com>
Commit-Queue: Joel Fernandes <joelaf@google.com>
(cherry picked from commit 2cf50ca2e7c3bc08f5182fc517a89a65e8dca7e3)
[Cherry picked from chromeos-5.15 tree. Minor tweaks to commit message
to match Android style]
Signed-off-by: Qais Yousef <qyousef@google.com>
This commit is contained in:
Vineeth Pillai
2022-10-16 16:22:56 +00:00
committed by Treehugger Robot
parent e0297c38a5
commit f4abe7bb5f
1 changed files with 52 additions and 0 deletions
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52
kernel/rcu/tree_nocb.h
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@@ -1215,6 +1215,55 @@ int rcu_nocb_cpu_offload(int cpu)
}
EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload);
static unsigned long
lazy_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
{
int cpu;
unsigned long count = 0;
/* Snapshot count of all CPUs */
for_each_possible_cpu(cpu) {
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
count += READ_ONCE(rdp->lazy_len);
}
return count ? count : SHRINK_EMPTY;
}
static unsigned long
lazy_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
{
int cpu;
unsigned long flags;
unsigned long count = 0;
/* Snapshot count of all CPUs */
for_each_possible_cpu(cpu) {
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
int _count = READ_ONCE(rdp->lazy_len);
if (_count == 0)
continue;
rcu_nocb_lock_irqsave(rdp, flags);
WRITE_ONCE(rdp->lazy_len, 0);
rcu_nocb_unlock_irqrestore(rdp, flags);
wake_nocb_gp(rdp, false);
sc->nr_to_scan -= _count;
count += _count;
if (sc->nr_to_scan <= 0)
break;
}
return count ? count : SHRINK_STOP;
}
static struct shrinker lazy_rcu_shrinker = {
.count_objects = lazy_rcu_shrink_count,
.scan_objects = lazy_rcu_shrink_scan,
.batch = 0,
.seeks = DEFAULT_SEEKS,
};
void __init rcu_init_nohz(void)
{
int cpu;
@@ -1240,6 +1289,9 @@ void __init rcu_init_nohz(void)
cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask);
#endif /* #if defined(CONFIG_NO_HZ_FULL) */
if (register_shrinker(&lazy_rcu_shrinker))
pr_err("Failed to register lazy_rcu shrinker!\n");
if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n");
cpumask_and(rcu_nocb_mask, cpu_possible_mask,