scx_layered: Add helper for layer slice duration #918
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Add a helper for returning the appropriate slice duration for a layer and replace a various instances where the slice value was being recalculated. Signed-off-by: Daniel Hodges <[email protected]>
| if (vtime_before(vtime, layer->vtime_now - layer_slice_ns)) | ||
| vtime = layer->vtime_now - layer_slice_ns; | ||
| if (vtime_before(vtime, layer->vtime_now - slice_ns)) | ||
| vtime = layer->vtime_now - slice_ns; | ||
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| /* | ||
| * Special-case per-cpu kthreads which aren't in a preempting layer so |
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I think this could potentially change the slice duration here as slice_ns variable is reused for kthreads. However, it should get set to the appropriate layers slice_ns vs the default which I think is reasonable.
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Looks good to me, assuming that the instance of slice_ns in main.bpf.c:1114 being shadowed by the new value is fine as you mention.
I would agree that it makes sense for the kthread to use the slice of the layer it's in. IMO if we were treating kthreads as a special case within the layer, then just passing them the standard slice would not be enough - we'd need a specific separate policy we can tune. In that case, we might as well put them in their own layer.
Add a helper for returning the appropriate slice duration for a layer and replace a various instances where the slice value was being recalculated.