From: Frederic Weisbecker <fweisbec@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Byungchul Park <byungchul.park@lge.com>,
Chris Metcalf <cmetcalf@ezchip.com>,
Thomas Gleixner <tglx@linutronix.de>,
Luiz Capitulino <lcapitulino@redhat.com>,
Christoph Lameter <cl@linux.com>,
"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
Mike Galbraith <efault@gmx.de>, Rik van Riel <riel@redhat.com>,
Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH 3/4] sched: Optimize tick periodic cpu load updates
Date: Sat, 2 Apr 2016 14:38:29 +0200 [thread overview]
Message-ID: <20160402123828.GC27395@lerouge> (raw)
In-Reply-To: <20160402072337.GF2906@worktop>
On Sat, Apr 02, 2016 at 09:23:37AM +0200, Peter Zijlstra wrote:
> On Fri, Apr 01, 2016 at 03:23:06PM +0200, Frederic Weisbecker wrote:
> > Don't bother with the whole pending tickless cpu load machinery if
> > we run a tick periodic kernel. That's less job for the CPU on ticks.
>
> Again, the changelog really could use help. Is this a pure optimization
> patch? If so, do you have numbers?
Well until now we have always tried to keep the nohz code under ifdef.
For optimizations and kernel size. I haven't measured it though, I guess
the gain is hardly visible.
>
> > +++ b/kernel/sched/sched.h
> > @@ -585,8 +585,10 @@ struct rq {
> > #endif
> > #define CPU_LOAD_IDX_MAX 5
> > unsigned long cpu_load[CPU_LOAD_IDX_MAX];
> > +#ifdef CONFIG_NO_HZ_COMMON
> > +# ifdef CONFIG_SMP
>
> I'm not a fan of this #ifdef indenting and nothing near there uses this
> style, so please don't introduce it here.
Ok.
Thanks.
>
> > unsigned long last_load_update_tick;
> > -#ifdef CONFIG_NO_HZ_COMMON
> > +# endif
> > u64 nohz_stamp;
> > unsigned long nohz_flags;
> > #endif
> > --
> > 2.7.0
> >
next prev parent reply other threads:[~2016-04-02 12:38 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-01 13:23 [PATCH 0/4] sched: Fix/improve nohz cpu load updates Frederic Weisbecker
2016-04-01 13:23 ` [PATCH 1/4] sched: Gather cpu load functions under a common namespace Frederic Weisbecker
2016-04-02 7:09 ` Peter Zijlstra
2016-04-02 12:28 ` Frederic Weisbecker
2016-04-01 13:23 ` [PATCH 2/4] sched: Correctly handle nohz ticks cpu load accounting Frederic Weisbecker
2016-04-02 7:15 ` Peter Zijlstra
2016-04-02 12:32 ` Frederic Weisbecker
2016-04-01 13:23 ` [PATCH 3/4] sched: Optimize tick periodic cpu load updates Frederic Weisbecker
2016-04-02 7:23 ` Peter Zijlstra
2016-04-02 12:38 ` Frederic Weisbecker [this message]
2016-04-01 13:23 ` [PATCH 4/4] sched: Conditionally build cpu load decay code for nohz Frederic Weisbecker
2016-04-02 7:23 ` Peter Zijlstra
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