* Jonathan Haslam <jonathan.haslam@xxxxxxxxx> wrote: > Active uprobes are stored in an RB tree and accesses to this tree are > dominated by read operations. Currently these accesses are serialized by > a spinlock but this leads to enormous contention when large numbers of > threads are executing active probes. > > This patch converts the spinlock used to serialize access to the > uprobes_tree RB tree into a reader-writer spinlock. This lock type > aligns naturally with the overwhelmingly read-only nature of the tree > usage here. Although the addition of reader-writer spinlocks are > discouraged [0], this fix is proposed as an interim solution while an > RCU based approach is implemented (that work is in a nascent form). This > fix also has the benefit of being trivial, self contained and therefore > simple to backport. > > This change has been tested against production workloads that exhibit > significant contention on the spinlock and an almost order of magnitude > reduction for mean uprobe execution time is observed (28 -> 3.5 microsecs). Have you considered/measured per-CPU RW semaphores? Thanks, Ingo
