From: Nagarathnam Muthusamy <nagarathnam.muthusamy@xxxxxxxxxx>
Date: Mon, 26 Jun 2017 12:39:27 -0400
> +static notrace inline u64
> +vgetsns(struct vvar_data *vvar)
> +{
> + u64 v;
> + u64 cycles;
> +
> + switch (vvar->vclock_mode) {
> + case VCLOCK_TICK:
> + cycles = vread_tick();
> + break;
> + case VCLOCK_STICK:
> + cycles = vread_stick();
> + break;
> + default:
> + return 0;
> + }
> + v = (cycles - vvar->clock.cycle_last) & vvar->clock.mask;
> + return v * vvar->clock.mult;
> +}
If you're going to go through all of this trouble to make a vdso,
it should be assembler code patched at boot time for the tick
access etc.
It is wasteful to run this switch statement when on a given
machine it will evaluate to the same value always.
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