From: Rusty Russell <rusty@rustcorp.com.au>
To: Avi Kivity <avi@redhat.com>
Cc: "kvm-devel" <kvm@vger.kernel.org>,
linux-kernel@vger.kernel.org, Mike Travis <travis@sgi.com>
Subject: Re: [PATCH 2/2] kvm: use cpumask_var_t for cpus_hardware_enabled
Date: Mon, 8 Dec 2008 16:35:34 +1030 [thread overview]
Message-ID: <200812081635.35166.rusty@rustcorp.com.au> (raw)
In-Reply-To: <493BF206.4070007@redhat.com>
On Monday 08 December 2008 02:25:50 Avi Kivity wrote:
> Rusty Russell wrote:
> > This changes cpus_hardware_enabled from a cpumask_t to a cpumask_var_t:
> > equivalent for CONFIG_CPUMASKS_OFFSTACK=n, otherwise dynamically allocated.
> >
> >
> > -static cpumask_t cpus_hardware_enabled;
> > +static cpumask_var_t cpus_hardware_enabled
>
> This isn't on stack, so it isn't buying us anything.
It's the CONFIG_NR_CPUS=4096 but nr_cpu_ids=4 case which we win using
dynamic allocation. Gotta love distribution kernels.
> Is the plan to drop cpumask_t?
Yes. And undefine 'struct cpumask' if CONFIG_CPUMASK_OFFSTACK. That
will stop assignment and on-stack declarations for all but the most
determined.
> If so, we're penalizing non-stack users
> by forcing them to go through another pointer (and cacheline).
Not quite. If !CONFIG_CPUMASK_OFFSTACK, cpumask_var_t == cpumask_t[1].
Blame Linus :)
Cheers,
Rusty.
next prev parent reply other threads:[~2008-12-08 6:05 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200812072125.45757.rusty@rustcorp.com.au>
2008-12-07 15:55 ` [PATCH 2/2] kvm: use cpumask_var_t for cpus_hardware_enabled Avi Kivity
2008-12-08 6:05 ` Rusty Russell [this message]
2008-12-08 9:46 ` Avi Kivity
2008-12-08 11:50 ` Rusty Russell
2008-12-08 14:29 ` Mike Travis
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