From: "Zhang, Qiang" <Qiang.Zhang@windriver.com>
To: "Uladzislau Rezki (Sony)" <urezki@gmail.com>,
LKML <linux-kernel@vger.kernel.org>, RCU <rcu@vger.kernel.org>,
"Paul E . McKenney" <paulmck@kernel.org>,
Michael Ellerman <mpe@ellerman.id.au>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Daniel Axtens <dja@axtens.net>,
Frederic Weisbecker <frederic@kernel.org>,
Neeraj Upadhyay <neeraju@codeaurora.org>,
Joel Fernandes <joel@joelfernandes.org>,
Peter Zijlstra <peterz@infradead.org>,
Michal Hocko <mhocko@suse.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Theodore Y . Ts'o" <tytso@mit.edu>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Subject: 回复: [PATCH 3/3] kvfree_rcu: use migrate_disable/enable()
Date: Sat, 23 Jan 2021 09:31:30 +0000 [thread overview]
Message-ID: <BYAPR11MB263252B1BD73A38DD8C0AF4EFFBF0@BYAPR11MB2632.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20210120162148.1973-3-urezki@gmail.com>
>________________________________________
>发件人: Uladzislau Rezki (Sony) <urezki@gmail.com>
>发送时间: 2021年1月21日 0:21
>收件人: LKML; RCU; Paul E . McKenney; Michael Ellerman
>抄送: Andrew Morton; Daniel Axtens; Frederic Weisbecker; Neeraj >Upadhyay; Joel Fernandes; Peter Zijlstra; Michal Hocko; Thomas >Gleixner; Theodore Y . Ts'o; Sebastian Andrzej Siewior; Uladzislau >Rezki; Oleksiy Avramchenko
>主题: [PATCH 3/3] kvfree_rcu: use migrate_disable/enable()
>
>Since the page is obtained in a fully preemptible context, dropping
>the lock can lead to migration onto another CPU. As a result a prev.
>bnode of that CPU may be underutilised, because a decision has been
>made for a CPU that was run out of free slots to store a pointer.
>
>migrate_disable/enable() are now independent of RT, use it in order
>to prevent any migration during a page request for a specific CPU it
>is requested for.
Hello Rezki
The critical migrate_disable/enable() area is not allowed to block, under RT and non RT.
There is such a description in preempt.h
* Notes on the implementation.
*
* The implementation is particularly tricky since existing code patterns
* dictate neither migrate_disable() nor migrate_enable() is allowed to block.
* This means that it cannot use cpus_read_lock() to serialize against hotplug,
* nor can it easily migrate itself into a pending affinity mask change on
* migrate_enable().
How about the following changes:
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e7a226abff0d..2aa19537ac7c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3488,12 +3488,10 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
(*krcp)->bkvhead[idx]->nr_records == KVFREE_BULK_MAX_ENTR) {
bnode = get_cached_bnode(*krcp);
if (!bnode && can_alloc) {
- migrate_disable();
krc_this_cpu_unlock(*krcp, *flags);
bnode = (struct kvfree_rcu_bulk_data *)
__get_free_page(GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOMEMALLOC | __GFP_NOWARN);
- *krcp = krc_this_cpu_lock(flags);
- migrate_enable();
+ raw_spin_lock_irqsave(&(*krcp)->lock, *flags);
}
if (!bnode)
Thanks
Qiang
>
>Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
>---
> kernel/rcu/tree.c | 2 ++
>1 file changed, 2 insertions(+)
>
>diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
>index 454809514c91..cad36074366d 100644
>--- a/kernel/rcu/tree.c
>+++ b/kernel/rcu/tree.c
>@@ -3489,10 +3489,12 @@ add_ptr_to_bulk_krc_lock(struct >kfree_rcu_cpu **krcp,
> (*krcp)->bkvhead[idx]->nr_records == >KVFREE_BULK_MAX_ENTR) {
> bnode = get_cached_bnode(*krcp);
> if (!bnode && can_alloc) {
>+ migrate_disable();
> krc_this_cpu_unlock(*krcp, *flags);
> bnode = (struct kvfree_rcu_bulk_data *)
> __get_free_page(GFP_KERNEL | >__GFP_RETRY_MAYFAIL | __GFP_NOMEMALLOC | __GFP_NOWARN);
> *krcp = krc_this_cpu_lock(flags);
>+ migrate_enable();
> }
>
> if (!bnode)
>--
>2.20.1
next prev parent reply other threads:[~2021-01-23 9:33 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-20 16:21 [PATCH 1/3] kvfree_rcu: Allocate a page for a single argument Uladzislau Rezki (Sony)
2021-01-20 16:21 ` [PATCH 2/3] kvfree_rcu: Use __GFP_NOMEMALLOC for single-argument kvfree_rcu() Uladzislau Rezki (Sony)
2021-01-28 18:06 ` Uladzislau Rezki
2021-01-20 16:21 ` [PATCH 3/3] kvfree_rcu: use migrate_disable/enable() Uladzislau Rezki (Sony)
2021-01-20 19:45 ` Sebastian Andrzej Siewior
2021-01-20 21:42 ` Paul E. McKenney
2021-01-23 9:31 ` Zhang, Qiang [this message]
2021-01-24 21:57 ` 回复: " Uladzislau Rezki
2021-01-25 1:50 ` 回复: " Zhang, Qiang
2021-01-25 2:18 ` Zhang, Qiang
2021-01-25 13:49 ` Uladzislau Rezki
2021-01-26 9:33 ` 回复: " Zhang, Qiang
2021-01-26 13:43 ` Uladzislau Rezki
2021-01-20 18:40 ` [PATCH 1/3] kvfree_rcu: Allocate a page for a single argument Paul E. McKenney
2021-01-20 19:57 ` Sebastian Andrzej Siewior
2021-01-20 21:54 ` Paul E. McKenney
2021-01-21 13:35 ` Uladzislau Rezki
2021-01-21 15:07 ` Paul E. McKenney
2021-01-21 19:17 ` Uladzislau Rezki
2021-01-22 11:17 ` Sebastian Andrzej Siewior
2021-01-22 15:28 ` Paul E. McKenney
2021-01-21 12:38 ` Uladzislau Rezki
2021-01-22 11:34 ` Sebastian Andrzej Siewior
2021-01-22 14:21 ` Uladzislau Rezki
2021-01-25 13:22 ` Michal Hocko
2021-01-25 14:31 ` Uladzislau Rezki
2021-01-25 15:39 ` Michal Hocko
2021-01-25 16:25 ` Uladzislau Rezki
2021-01-28 15:11 ` Uladzislau Rezki
2021-01-28 15:17 ` Michal Hocko
2021-01-28 15:30 ` Uladzislau Rezki
2021-01-28 18:02 ` Uladzislau Rezki
[not found] ` <YBPNvbJLg56XU8co@dhcp22.suse.cz>
2021-01-29 16:35 ` Uladzislau Rezki
2021-02-01 11:47 ` Michal Hocko
2021-02-01 14:44 ` Uladzislau Rezki
2021-02-03 19:37 ` Paul E. McKenney
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=BYAPR11MB263252B1BD73A38DD8C0AF4EFFBF0@BYAPR11MB2632.namprd11.prod.outlook.com \
--to=qiang.zhang@windriver.com \
--cc=akpm@linux-foundation.org \
--cc=bigeasy@linutronix.de \
--cc=dja@axtens.net \
--cc=frederic@kernel.org \
--cc=joel@joelfernandes.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mhocko@suse.com \
--cc=mpe@ellerman.id.au \
--cc=neeraju@codeaurora.org \
--cc=oleksiy.avramchenko@sonymobile.com \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=rcu@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=tytso@mit.edu \
--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).