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> > > > > > > > > > This should be a NODEMASK_ALLOC(). We don't want to eat up too much of the > > > > > stack, right? > > > > > > > > Ok, and if I want to initialize unvisited to all online nodes, is there a > > > > better than doing: > > > > > > > > nodemask_clear(*unvisited); > > > > nodemask_or(*unvisited, *unvisited, node_states[N_ONLINE]); > > > > > > > > We don't have nodemask_copy() right? > > > > > > Sorry, and with that I mean nodes_clear() / nodes_or() / nodes_copy(). > > > > Also, it might be problematic to use NODEMASK_ALLOC() here, since we're > > potentially holding raw spinlocks. Maybe we could use per-cpu nodemask_t, > > but then we need to preempt_disable() the entire loop, since > > scx_pick_idle_cpu() can be be called potentially from any context. > > > > Considering that the maximum value for NODE_SHIFT is 10 with CONFIG_MAXSMP, > > nodemask_t should be 128 bytes at most, that doesn't seem too bad... Maybe > > we can accept to have it on the stack in this case? > > If you expect calling this in strict SMP lock-held or IRQ contexts, You > need to be careful about stack overflow even mode. We've got GFP_ATOMIC > for that: > non sleeping allocation with an expensive fallback so it can access > some portion of memory reserves. Usually used from interrupt/bottom-half > context with an expensive slow path fallback. > > Check Documentation/core-api/memory-allocation.rst for other options. > You may be interested in __GFP_NORETRY as well. I know about GFP_ATOMIC, but even with that I'm hitting some bugs. Will try with __GFP_NORETRY. Thanks, -Andrea