Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCH 2/2] kvm: use cpumask_var_t for cpus_hardware_enabled | Date | Mon, 8 Dec 2008 22:20:42 +1030 |
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On Monday 08 December 2008 20:16:44 Avi Kivity wrote: > Rusty Russell wrote: > >> 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. > > > > > > What does it buy? 4096/8 = 512 bytes statically allocated?
It adds up, and 4096 seems to be only the start of the insanityH^H^Hfun.
> > Not quite. If !CONFIG_CPUMASK_OFFSTACK, cpumask_var_t == cpumask_t[1]. > > Blame Linus :) > > > > Hm, is there a C trick which will error out when allocating something on > the stack, but work when allocating statically? I can think of > something to do the reverse, but that doesn't help.
We also need to prevent assignment, eg:
*foo = *bar;
Because when we allocate them, we'll cut them to size.
Cheers, Rusty.
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