From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Lai Jiangshan <laijs@linux.alibaba.com>
Cc: linux-kernel@vger.kernel.org,
Lai Jiangshan <laijs@linux.alibaba.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, "Paul E. McKenney" <paulmck@kernel.org>,
Josh Triplett <josh@joshtriplett.org>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
Andi Kleen <ak@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Fenghua Yu <fenghua.yu@intel.com>,
Kees Cook <keescook@chromium.org>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Babu Moger <Babu.Moger@amd.com>, Rik van Riel <riel@surriel.com>,
"Chang S. Bae" <chang.seok.bae@intel.com>,
Jann Horn <jannh@google.com>, David Windsor <dwindsor@gmail.com>,
Elena Reshetova <elena.reshetova@intel.com>,
Yuyang Du <duyuyang@gmail.com>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Richard Guy Briggs <rgb@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Christian Brauner <christian.brauner@ubuntu.com>,
Michal Hocko <mhocko@suse.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>,
"Dmitry V. Levin" <ldv@altlinux.org>,
rcu@vger.kernel.org
Subject: Re: [PATCH V2 7/7] x86,rcu: use percpu rcu_preempt_depth
Date: Mon, 4 Nov 2019 10:25:19 +0100 [thread overview]
Message-ID: <20191104092519.nukaz5qmgiskzafi@linutronix.de> (raw)
In-Reply-To: <20191102124559.1135-8-laijs@linux.alibaba.com>
On 2019-11-02 12:45:59 [+0000], Lai Jiangshan wrote:
> Convert x86 to use a per-cpu rcu_preempt_depth. The reason for doing so
> is that accessing per-cpu variables is a lot cheaper than accessing
> task_struct or thread_info variables.
Is there a benchmark saying how much we gain from this?
> We need to save/restore the actual rcu_preempt_depth when switch.
> We also place the per-cpu rcu_preempt_depth close to __preempt_count
> and current_task variable.
>
> Using the idea of per-cpu __preempt_count.
>
> No function call when using rcu_read_[un]lock().
> Single instruction for rcu_read_lock().
> 2 instructions for fast path of rcu_read_unlock().
I think these were not inlined due to the header requirements.
Boris pointed one thing, there is also DEFINE_PERCPU_RCU_PREEMP_DEPTH.
Sebastian
next prev parent reply other threads:[~2019-11-04 9:26 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-02 12:45 [PATCH V2 0/7] rcu: introduce percpu rcu_preempt_depth Lai Jiangshan
2019-11-02 12:45 ` [PATCH V2 1/7] rcu: use preempt_count to test whether scheduler locks is held Lai Jiangshan
2019-11-15 16:53 ` Paul E. McKenney
2020-02-19 3:31 ` Joel Fernandes
2020-02-19 3:59 ` Paul E. McKenney
2019-11-02 12:45 ` [PATCH V2 2/7] rcu: cleanup rcu_preempt_deferred_qs() Lai Jiangshan
2019-11-03 2:01 ` Boqun Feng
2019-11-03 5:01 ` Lai Jiangshan
2019-11-04 14:55 ` Paul E. McKenney
2019-11-05 2:09 ` Lai Jiangshan
2019-11-05 7:19 ` Paul E. McKenney
2019-11-11 14:32 ` Paul E. McKenney
2019-11-12 1:28 ` Lai Jiangshan
2020-02-17 23:23 ` Paul E. McKenney
2020-02-18 14:41 ` Steven Rostedt
2020-02-18 16:43 ` Paul E. McKenney
2019-11-15 16:55 ` Paul E. McKenney
2019-11-02 12:45 ` [PATCH V2 3/7] rcu: remove useless special.b.deferred_qs Lai Jiangshan
2020-02-17 23:23 ` Paul E. McKenney
2019-11-02 12:45 ` [PATCH V2 4/7] rcu: don't use negative ->rcu_read_lock_nesting Lai Jiangshan
2020-02-17 23:26 ` Paul E. McKenney
2019-11-02 12:45 ` [PATCH V2 5/7] rcu: wrap usages of rcu_read_lock_nesting Lai Jiangshan
2019-11-15 22:25 ` Paul E. McKenney
2019-11-02 12:45 ` [PATCH V2 6/7] rcu: clear the special.b.need_qs in rcu_note_context_switch() Lai Jiangshan
2019-11-16 15:46 ` Paul E. McKenney
2019-11-02 12:45 ` [PATCH V2 7/7] x86,rcu: use percpu rcu_preempt_depth Lai Jiangshan
2019-11-02 16:30 ` Borislav Petkov
2019-11-03 4:33 ` Lai Jiangshan
2019-11-04 9:25 ` Sebastian Andrzej Siewior [this message]
2019-11-04 11:41 ` Lai Jiangshan
2019-11-04 12:09 ` Sebastian Andrzej Siewior
2019-11-16 15:48 ` Paul E. McKenney
2019-11-18 2:02 ` Lai Jiangshan
2019-11-18 14:59 ` Paul E. McKenney
2019-11-19 1:59 ` Lai Jiangshan
2019-11-19 21:14 ` Paul E. McKenney
2019-11-20 2:47 ` Lai Jiangshan
2019-11-21 4:02 ` Paul E. McKenney
2019-11-02 15:05 ` [PATCH V2 0/7] rcu: introduce " 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=20191104092519.nukaz5qmgiskzafi@linutronix.de \
--to=bigeasy@linutronix.de \
--cc=Babu.Moger@amd.com \
--cc=aarcange@redhat.com \
--cc=ak@linux.intel.com \
--cc=akpm@linux-foundation.org \
--cc=anshuman.khandual@arm.com \
--cc=bp@alien8.de \
--cc=chang.seok.bae@intel.com \
--cc=christian.brauner@ubuntu.com \
--cc=dave.hansen@intel.com \
--cc=duyuyang@gmail.com \
--cc=dwindsor@gmail.com \
--cc=elena.reshetova@intel.com \
--cc=fenghua.yu@intel.com \
--cc=hpa@zytor.com \
--cc=jannh@google.com \
--cc=jiangshanlai@gmail.com \
--cc=joel@joelfernandes.org \
--cc=josh@joshtriplett.org \
--cc=keescook@chromium.org \
--cc=laijs@linux.alibaba.com \
--cc=ldv@altlinux.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=mhocko@suse.com \
--cc=mingo@redhat.com \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=rafael.j.wysocki@intel.com \
--cc=rcu@vger.kernel.org \
--cc=rgb@redhat.com \
--cc=riel@surriel.com \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
--cc=viro@zeniv.linux.org.uk \
--cc=x86@kernel.org \
/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).