From: Eric Dumazet <eric.dumazet@gmail.com>
To: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>,
Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Andi Kleen <ak@linux.intel.com>,
Venki Pallipadi <venki@google.com>
Subject: Re: [Patch] Idle balancer: cache align nohz structure to improve idle load balancing scalability
Date: Thu, 20 Oct 2011 08:43:06 +0200 [thread overview]
Message-ID: <1319092986.8416.50.camel@edumazet-laptop> (raw)
In-Reply-To: <1319090264.14569.1.camel@sbsiddha-mobl2>
Le mercredi 19 octobre 2011 à 22:57 -0700, Suresh Siddha a écrit :
> On Wed, 2011-10-19 at 21:18 -0700, Eric Dumazet wrote:
> > > + atomic_t load_balancer ____cacheline_aligned;
> > > + atomic_t first_pick_cpu ____cacheline_aligned;
> > > + atomic_t second_pick_cpu ____cacheline_aligned;
> > > + cpumask_var_t idle_cpus_mask ____cacheline_aligned;
> > > cpumask_var_t grp_idle_mask;
> > > unsigned long next_balance; /* in jiffy units */
> > > } nohz ____cacheline_aligned;
> > >
> >
> > Dont you increase cache footprint, say for an Uniprocessor machine ?
> >
> > (CONFIG_SMP=n)
> >
> > ____cacheline_aligned_in_smp seems more suitable in this case.
>
> I believe this code is already under ifdef CONFIG_SMP.
Right now yes, but it might change in the future after some code
cleanup / consolidation.
This kind of things are copy/pasted, and the right semantic here is
____cacheline_aligned_in_smp . It matches the changelog better.
Note: the ____cacheline_aligned on global "nohz" structure was quite
different, and in contradiction of what this patch wants to do.
Previously, we wanted to group all fields on a single cache line.
We now know it was not a scalable strategy, thanks to Tim.
next prev parent reply other threads:[~2011-10-20 6:43 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-19 21:45 Tim Chen
2011-10-20 4:18 ` Eric Dumazet
2011-10-20 5:57 ` Suresh Siddha
2011-10-20 6:43 ` Eric Dumazet [this message]
2011-10-20 17:19 ` Tim Chen
2011-10-20 4:24 ` Andi Kleen
2011-10-20 12:26 ` Venki Pallipadi
2011-10-20 17:31 ` Suresh Siddha
2011-10-20 17:38 ` Peter Zijlstra
[not found] ` <4FF5AC937153B0459463C1A88EB478F20135D6ECB5@orsmsx505.amr.corp.intel.com>
2011-11-01 23:52 ` Suresh Siddha
2011-11-02 13:04 ` Srivatsa Vaddagiri
2011-11-02 13:54 ` Srivatsa Vaddagiri
2011-11-02 15:13 ` Suresh Siddha
2011-11-14 9:32 ` Peter Zijlstra
2011-11-14 19:37 ` Suresh Siddha
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