On Thu, Nov 30, 2023 at 03:43:26PM -0500, Waiman Long wrote: > The current design of cgroup_rstat_cpu_pop_updated() is to traverse > the updated tree in a way to pop out the leaf nodes first before > their parents. This can cause traversal of multiple nodes before a > leaf node can be found and popped out. IOW, a given node in the tree > can be visited multiple times before the whole operation is done. So > it is not very efficient and the code can be hard to read. > > With the introduction of cgroup_rstat_updated_list() to build a list > of cgroups to be flushed first before any flushing operation is being > done, we can optimize the way the updated tree nodes are being popped > by pushing the parents first to the tail end of the list before their > children. In this way, most updated tree nodes will be visited only > once with the exception of the subtree root as we still need to go > back to its parent and popped it out of its updated_children list. > This also makes the code easier to read. > > Signed-off-by: Waiman Long <longman@xxxxxxxxxx> Applied to cgroup/for-6.8 with a small comment edit. ... > + * Iteratively traverse down the cgroup_rstat_cpu updated tree level by > + * level and push all the parents first before their next level children > + * into a singly linked list built from the tail backward like "pushing" > + * cgroups into a stack. The parent is by the caller. I found the last sentence a bit difficult to understand and changed it to "The root is pushed by the caller." That's what you meant, right? Thanks. -- tejun
