scx_layered: Add override context for layer hinting #587
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Add thread hinting to scx_layered. Signed-off-by: Daniel Hodges <hodges.daniel.scott@gmail.com>
| @@ -162,4 +163,8 @@ struct layer { | |||
| unsigned int perf; | |||
| }; | |||
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| struct user_ctx { | |||
| u64 task_overrides[MAX_LAYER_OVERRIDES]; | |||
| u32 nr_overrides; | |||
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Can this have a generation number so that it doesn't have to be walked every time?
| @@ -314,6 +323,7 @@ struct task_ctx { | |||
| struct bpf_cpumask __kptr *layered_cpumask; | |||
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| bool all_cpus_allowed; | |||
| bool is_override; | |||
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and then this can be the copy of the generation number where it's only effective if it matches the current gen.
| @@ -162,4 +163,8 @@ struct layer { | |||
| unsigned int perf; | |||
| }; | |||
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| struct user_ctx { | |||
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Given that we have uid matches, user may be a bit confusing? How about just override_ctx or overrides.
hodgesds
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Updated with a some better names and some poor synchronization. There's now a way to yield tasks back to the scheduler which should be interesting. There's certainly some vruntime error introduced with user overrides though. |
Rename user_ctx to override_ctx and add a generation per layer. This should allow a rough synchronization with userspace. Signed-off-by: Daniel Hodges <hodges.daniel.scott@gmail.com>
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This will likely need to support pid namespaces, which will be... fun |
hodgesds
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| // To yield control back to the BPF scheduler userspace is | ||
| // allowed to yield a task. Reset all the yielded tasks. | ||
| bpf_for(i, 0, octx->nr_yields) { |
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When override gen changes, wouldn't that automatically revoke overrides of all tasks that aren't anymore in the current generation? ie. maybe_refresh_layer() can test whether its gen is behind the global gen and if so, revert back to the original layer and then clear the gen number to indicate that the situation has been dealt with.
| * p->scx.dsq_vtime = layer->vtime_now; | ||
| * | ||
| */ | ||
| tctx->layer = layer_idx; |
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So, the way to do this, I think, is just updating the generation numbers here and what the target index should be and let maybe_refresh_layer() do the actual update. That way, it'll update in a synchronized manner and vtime will be taken care of too.
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Yeah, I think that makes sense... keep the updates in one place.
Add thread hinting to scx_layered by a user mappable map that allows for overriding layers for a pid. There's no locking or safety ☠️ yet.