From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Lai Jiangshan <laijs@linux.alibaba.com>
Cc: linux-kernel@vger.kernel.org,
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 13:09:39 +0100 [thread overview]
Message-ID: <20191104120939.5e4hdcoat2v4jxov@linutronix.de> (raw)
In-Reply-To: <4878ccfd-7a4e-4f84-9bc3-1d477e077587@linux.alibaba.com>
On 2019-11-04 19:41:20 [+0800], Lai Jiangshan wrote:
> > Is there a benchmark saying how much we gain from this?
>
> Hello
>
> Maybe I can write a tight loop for testing, but I don't
> think anyone will be interesting in it.
>
> I'm also trying to find some good real tests. I need
> some suggestions here.
There is rcutorture but I don't know how much of performance test this
is, Paul would know.
A micro benchmark is one thing. Any visible changes in userland to
workloads like building a kernel or hackbench?
I don't argue that incrementing a per-CPU variable is more efficient
than reading a per-CPU variable, adding an offset and then incrementing
it. I was just curious to see if there are any numbers on it.
> > > 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.
>
> objdump -D -S kernel/workqueue.o shows (selected fractions):
That was not what I meant. To inline current rcu_read_lock() would mean
to include definition for struct task_struct (and everything down the
road) in the rcu headers which isn't working.
> Best regards
> Lai
Sebastian
next prev parent reply other threads:[~2019-11-04 12:10 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
2019-11-04 11:41 ` Lai Jiangshan
2019-11-04 12:09 ` Sebastian Andrzej Siewior [this message]
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
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