On Fri, 7 Mar 2025 10:56:04 -0500 Gregory Price <gourry@xxxxxxxxxx> wrote: Hi Gregory Thank you for your response regarding this patch. > On Fri, Mar 07, 2025 at 03:35:29PM +0900, Rakie Kim wrote: > > Unnecessary sysfs entries: Nodes without memory were included in sysfs > > at boot. > > Missing hotplug support: Nodes that became online after initialization > > were not recognized, causing incomplete interleave configurations. > > This comment is misleading. Nodes can "come online" but they are > absolutely detected during init - as nodes cannot be "hotplugged" > themselves. Resources can be added *to* nodes, but nodes themselves > cannot be added or removed. > > I think what you're trying to say here is: > > 1) The current system creates 1 entry per possible node (explicitly) > 2) Not all nodes may have memory at all times (memory can be hotplugged) > 3) It would be nice to let sysfs and weighted interleave omit memoryless > nodes until those nodes had memory hotplugged into them. > > > Dynamic sysfs updates for hotplugged nodes New memory nodes are > > recognized and integrated via the memory hotplug mechanism. > > Subsequent patches refine this functionality: > > > > Just going to reiterate that that there's no such this as a hotplug node > or "new nodes" - only nodes that have their attributes changed (i.e. > !N_MEMORY -> N_MEMORY). The node exists, it may just not have anything > associated with it. > > Maybe semantic nits, but it matters. The nodes are present and can be > operated on before memory comes online, and that has implications for > users. Depending on how that hardware comes online, it may or may not > report its performance data prior to memory hotplug. I agree with your assessment. The existing comments, as you pointed out, might indeed be confusing or misleading. I'll make sure this issue is addressed in version 2. > > If it doesn't report its performance data, then hiding the node before > it hotplugs memory means a user can't pre-configure the system for when > the memory is added (which could be used immediately). > > Hiding the node until hotplug also means we have hidden state. We need > to capture pre-hotplug reported performance data so that if it comes > online the auto-calculation of weights is correct. But if the user has > already switched from auto to manual mode, then a node suddenly > appearing will have an unknown state. > > This is why I initially chose to just expose N_POSSIBLE entries in > sysfs, because the transition state causes hidden information - and that > felt worse than extra entries. I suppose I should add some > documentation somewhere that discusses this issue. > > I think the underlying issue you're dealing with is that the system is > creating more nodes for you than it should. I will reply to your next comment on this issue soon. > > ~Gregory Rakie
