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scx_flatcg: Keep cgroup rb nodes stashed #168
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The flatcg scheduler uses a rb_node type - struct cgv_node - to keep track of vtime. On cgroup init, a cgv_node is created and stashed in a hashmap - cgv_node_stash - for later use. In cgroup_enqueued and try_pick_next_cgroup, the node is inserted into the rbtree, which required removing it from the stash before this patch's changes. This patch makes cgv_node refcounted, which allows keeping it in the stash for the entirety of the cgroup's lifetime. Unnecessary bpf_kptr_xchg's and other boilerplate can be removed as a result. Note that in addition to bpf_refcount patches, which have been upstream for quite some time, this change depends on a more recent series [0]. [0]: https://lore.kernel.org/bpf/[email protected]/ Signed-off-by: Dave Marchevsky <[email protected]>
Byte-Lab
approved these changes
Mar 28, 2024
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The flatcg scheduler uses a rb_node type - struct cgv_node - to keep track of vtime. On cgroup init, a cgv_node is created and stashed in a hashmap - cgv_node_stash - for later use. In cgroup_enqueued and try_pick_next_cgroup, the node is inserted into the rbtree, which required removing it from the stash before this patch's changes.
This patch makes cgv_node refcounted, which allows keeping it in the stash for the entirety of the cgroup's lifetime. Unnecessary bpf_kptr_xchg's and other boilerplate can be removed as a result.
Note that in addition to bpf_refcount patches, which have been upstream for quite some time, this change depends on a more recent series 0.