From: "Paul E. McKenney" <paulmck@kernel.org>
To: qiang.zhang@windriver.com
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, urezki@gmail.com
Subject: Re: [PATCH] rcu: Release per-cpu krcp page cache when CPU going offline
Date: Thu, 21 Jan 2021 10:56:15 -0800 [thread overview]
Message-ID: <20210121185615.GR2743@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20210121064949.16164-1-qiang.zhang@windriver.com>
On Thu, Jan 21, 2021 at 02:49:49PM +0800, qiang.zhang@windriver.com wrote:
> From: Zqiang <qiang.zhang@windriver.com>
>
> If CPUs go offline, the corresponding krcp's page cache can
> not be use util the CPU come back online, or maybe the CPU
> will never go online again, this commit therefore free krcp's
> page cache when CPUs go offline.
>
> Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Adding Uladzislau on CC for his thoughts.
Thanx, Paul
> ---
> kernel/rcu/tree.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 46 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index e04e336bee42..2eaf6f287483 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -158,6 +158,9 @@ static void sync_sched_exp_online_cleanup(int cpu);
> static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp);
> static bool rcu_rdp_is_offloaded(struct rcu_data *rdp);
>
> +static void krc_offline(unsigned int cpu, bool off);
> +static void free_krc_page_cache(int cpu);
> +
> /* rcuc/rcub kthread realtime priority */
> static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0;
> module_param(kthread_prio, int, 0444);
> @@ -2457,6 +2460,9 @@ int rcutree_dead_cpu(unsigned int cpu)
>
> // Stop-machine done, so allow nohz_full to disable tick.
> tick_dep_clear(TICK_DEP_BIT_RCU);
> +
> + krc_offline(cpu, true);
> + free_krc_page_cache(cpu);
> return 0;
> }
>
> @@ -3169,6 +3175,7 @@ struct kfree_rcu_cpu {
>
> struct llist_head bkvcache;
> int nr_bkv_objs;
> + bool offline;
> };
>
> static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc) = {
> @@ -3220,6 +3227,8 @@ static inline bool
> put_cached_bnode(struct kfree_rcu_cpu *krcp,
> struct kvfree_rcu_bulk_data *bnode)
> {
> + if (krcp->offline)
> + return false;
> // Check the limit.
> if (krcp->nr_bkv_objs >= rcu_min_cached_objs)
> return false;
> @@ -3230,6 +3239,39 @@ put_cached_bnode(struct kfree_rcu_cpu *krcp,
>
> }
>
> +static void krc_offline(unsigned int cpu, bool off)
> +{
> + unsigned long flags;
> + struct kfree_rcu_cpu *krcp;
> +
> + krcp = per_cpu_ptr(&krc, cpu);
> + raw_spin_lock_irqsave(&krcp->lock, flags);
> + if (off)
> + krcp->offline = true;
> + else
> + krcp->offline = false;
> + raw_spin_unlock_irqrestore(&krcp->lock, flags);
> +}
> +
> +static void free_krc_page_cache(int cpu)
> +{
> + unsigned long flags;
> + struct kfree_rcu_cpu *krcp;
> + int i;
> + struct kvfree_rcu_bulk_data *bnode;
> +
> + krcp = per_cpu_ptr(&krc, cpu);
> +
> + for (i = 0; i < rcu_min_cached_objs; i++) {
> + raw_spin_lock_irqsave(&krcp->lock, flags);
> + bnode = get_cached_bnode(krcp);
> + raw_spin_unlock_irqrestore(&krcp->lock, flags);
> + if (!bnode)
> + break;
> + free_page((unsigned long)bnode);
> + }
> +}
> +
> /*
> * This function is invoked in workqueue context after a grace period.
> * It frees all the objects queued on ->bhead_free or ->head_free.
> @@ -3549,7 +3591,8 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
> kasan_record_aux_stack(ptr);
> success = kvfree_call_rcu_add_ptr_to_bulk(krcp, ptr);
> if (!success) {
> - run_page_cache_worker(krcp);
> + if (!krcp->offline)
> + run_page_cache_worker(krcp);
>
> if (head == NULL)
> // Inline if kvfree_rcu(one_arg) call.
> @@ -4086,6 +4129,7 @@ int rcutree_prepare_cpu(unsigned int cpu)
> rcu_spawn_cpu_nocb_kthread(cpu);
> WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus + 1);
>
> + krc_offline(cpu, false);
> return 0;
> }
>
> @@ -4591,6 +4635,7 @@ static void __init kfree_rcu_batch_init(void)
> INIT_DELAYED_WORK(&krcp->monitor_work, kfree_rcu_monitor);
> INIT_WORK(&krcp->page_cache_work, fill_page_cache_func);
> krcp->initialized = true;
> + krcp->offline = true;
> }
> if (register_shrinker(&kfree_rcu_shrinker))
> pr_err("Failed to register kfree_rcu() shrinker!\n");
> --
> 2.29.2
>
next prev parent reply other threads:[~2021-01-21 19:31 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-21 6:49 [PATCH] rcu: Release per-cpu krcp page cache when CPU going offline qiang.zhang
2021-01-21 18:56 ` Paul E. McKenney [this message]
2021-01-21 20:26 ` Uladzislau Rezki
2021-01-22 1:44 ` 回复: " Zhang, Qiang
2021-01-22 14:31 ` Uladzislau Rezki
2021-01-24 2:21 ` 回复: " Zhang, Qiang
2021-01-24 17:42 ` Uladzislau Rezki
2021-01-26 14:07 ` Uladzislau Rezki
2021-01-27 9:00 ` 回复: " Zhang, Qiang
2021-01-27 12:47 ` Uladzislau Rezki
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210121185615.GR2743@paulmck-ThinkPad-P72 \
--to=paulmck@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=qiang.zhang@windriver.com \
--cc=rcu@vger.kernel.org \
--cc=urezki@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).