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From: Nicholas Piggin <nicholas.piggin@gmail.com>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
	jiangshanlai@gmail.com, dipankar@in.ibm.com,
	akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
	josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
	rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
	fweisbec@gmail.com, oleg@redhat.com, joel.opensrc@gmail.com,
	torvalds@linux-foundation.org, npiggin@gmail.com
Subject: Re: [PATCH tip/core/rcu 0/21] Contention reduction for v4.18
Date: Tue, 15 May 2018 08:21:20 +1000	[thread overview]
Message-ID: <20180515082120.1dbc32b5@roar.ozlabs.ibm.com> (raw)
In-Reply-To: <20180514160907.GX26088@linux.vnet.ibm.com>

On Mon, 14 May 2018 09:09:07 -0700
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:

> On Mon, May 14, 2018 at 04:42:33PM +1000, Nicholas Piggin wrote:
> > On Sun, 22 Apr 2018 20:02:58 -0700
> > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
> >   
> > > Hello!
> > > 
> > > This series reduces lock contention on the root rcu_node
> > > structure, and is also the first precursor to TBD changes to
> > > consolidate the three RCU flavors (RCU-bh, RCU-preempt, and
> > > RCU-sched) into one.  
> > 
> > Hi Paul,
> > 
> > I've been running your rcu/dev branch and haven't noticed any
> > problems yet. The irqsoff latency improvement is a little hard to
> > measure because the scheduler, but I've tried turning balancing
> > parameters right down and I'm yet to see any sign of RCU in traces
> > (down to about 100us on a 176 CPU machine), so that's great.  
> 
> Good to hear!!!

Yep, as in, various other latencies are down to 100us, and still
no sign of RCU, so RCU must be sitting somewhere below that.


> > (Not that RCU was ever the worst contributor to latency as I said,
> > just that I noticed those couple of traces where it showed up.)
> > 
> > Thanks very much for the fast response, sorry I've taken a while to
> > test.  
> 
> Would you be willing to give me a Tested-by on that series of patches?

Yes of course, for your rcu/dev series

Tested-by: Nicholas Piggin <npiggin@gmail.com>

Let me know if you make any other changes you'd like me to test before
merge.

Thanks,
Nick

  reply	other threads:[~2018-05-14 22:21 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-23  3:02 [PATCH tip/core/rcu 0/21] Contention reduction for v4.18 Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 01/21] rcu: Improve non-root rcu_cbs_completed() accuracy Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 02/21] rcu: Make rcu_start_future_gp()'s grace-period check more precise Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 03/21] rcu: Add accessor macros for the ->need_future_gp[] array Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 04/21] rcu: Make rcu_gp_kthread() check for early-boot activity Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 05/21] rcu: Make rcu_gp_cleanup() more accurately predict need for new GP Paul E. McKenney
2018-05-10  7:21   ` [tip/core/rcu, " Joel Fernandes
2018-05-10 13:15     ` Paul E. McKenney
2018-05-10 17:22       ` Joel Fernandes
2018-05-11 16:22         ` Paul E. McKenney
2018-05-10 17:37       ` Joel Fernandes
2018-05-11 16:24         ` Paul E. McKenney
2018-05-11 16:27           ` Joel Fernandes
2018-04-23  3:03 ` [PATCH tip/core/rcu 06/21] rcu: Avoid losing ->need_future_gp[] values due to GP start/end races Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 07/21] rcu: Make rcu_future_needs_gp() check all ->need_future_gps[] elements Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 08/21] rcu: Convert ->need_future_gp[] array to boolean Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 09/21] rcu: Make rcu_migrate_callbacks wake GP kthread when needed Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 10/21] rcu: Avoid __call_rcu_core() root rcu_node ->lock acquisition Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 11/21] rcu: Switch __rcu_process_callbacks() to rcu_accelerate_cbs() Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 12/21] rcu: Cleanup, don't put ->completed into an int Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 13/21] rcu: Clear request other than RCU_GP_FLAG_INIT at GP end Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 14/21] rcu: Inline rcu_start_gp_advanced() into rcu_start_future_gp() Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 15/21] rcu: Make rcu_start_future_gp() caller select grace period Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 16/21] rcu: Add funnel locking to rcu_start_this_gp() Paul E. McKenney
2018-05-12  6:03   ` [tip/core/rcu,16/21] " Joel Fernandes
2018-05-12 14:40     ` Paul E. McKenney
2018-05-12 14:44       ` Paul E. McKenney
2018-05-12 23:53         ` Joel Fernandes
2018-05-13 15:38           ` Paul E. McKenney
2018-05-13 16:49             ` Joel Fernandes
2018-05-13 19:09               ` Paul E. McKenney
2018-05-13 19:51                 ` Joel Fernandes
2018-05-14  2:22                   ` Paul E. McKenney
2018-05-14  5:00                     ` Joel Fernandes
2018-05-14 13:23                       ` Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 17/21] rcu: Make rcu_start_this_gp() check for out-of-range requests Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 18/21] rcu: The rcu_gp_cleanup() function does not need cpu_needs_another_gp() Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 19/21] rcu: Simplify and inline cpu_needs_another_gp() Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 20/21] rcu: Drop early GP request check from rcu_gp_kthread() Paul E. McKenney
2018-04-23  3:03 ` [PATCH tip/core/rcu 21/21] rcu: Update list of rcu_future_grace_period() trace events Paul E. McKenney
2018-05-14  6:42 ` [PATCH tip/core/rcu 0/21] Contention reduction for v4.18 Nicholas Piggin
2018-05-14 16:09   ` Paul E. McKenney
2018-05-14 22:21     ` Nicholas Piggin [this message]
2018-05-14 22:42       ` Paul E. McKenney

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