From 67caea1fec85266590dddfa431e1cb000bc942f4 Mon Sep 17 00:00:00 2001 From: Mitko Haralanov Date: Thu, 12 May 2016 10:23:09 -0700 Subject: IB/hfi1: Improve performance of interval RB trees The interval RB tree management functions use handlers to store user-specific callback for the various tree operations. These handlers are put on a doubly-linked list. When a RB tree function is called, the list is searched for the handler of the particular tree. The list which holds the handlers is modified very rarely - when a handler is created and when a handler is removed. On the other hand, it is searched very often. This a perfect usage scenario for RCU. The result is a much lower overhead of traversing the list as most of the time no locking will be required. Reviewed-by: Dean Luick Reviewed-by: Mike Marciniszyn Signed-off-by: Mitko Haralanov Signed-off-by: Doug Ledford --- drivers/staging/rdma/hfi1/mmu_rb.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) (limited to 'drivers/staging') diff --git a/drivers/staging/rdma/hfi1/mmu_rb.c b/drivers/staging/rdma/hfi1/mmu_rb.c index 2b0e91d3093d..b7a80aa1ae30 100644 --- a/drivers/staging/rdma/hfi1/mmu_rb.c +++ b/drivers/staging/rdma/hfi1/mmu_rb.c @@ -45,6 +45,7 @@ * */ #include +#include #include #include @@ -97,7 +98,6 @@ static unsigned long mmu_node_last(struct mmu_rb_node *node) int hfi1_mmu_rb_register(struct rb_root *root, struct mmu_rb_ops *ops) { struct mmu_rb_handler *handlr; - unsigned long flags; if (!ops->invalidate) return -EINVAL; @@ -111,9 +111,9 @@ int hfi1_mmu_rb_register(struct rb_root *root, struct mmu_rb_ops *ops) INIT_HLIST_NODE(&handlr->mn.hlist); spin_lock_init(&handlr->lock); handlr->mn.ops = &mn_opts; - spin_lock_irqsave(&mmu_rb_lock, flags); - list_add_tail(&handlr->list, &mmu_rb_handlers); - spin_unlock_irqrestore(&mmu_rb_lock, flags); + spin_lock(&mmu_rb_lock); + list_add_tail_rcu(&handlr->list, &mmu_rb_handlers); + spin_unlock(&mmu_rb_lock); return mmu_notifier_register(&handlr->mn, current->mm); } @@ -130,9 +130,10 @@ void hfi1_mmu_rb_unregister(struct rb_root *root) if (current->mm) mmu_notifier_unregister(&handler->mn, current->mm); - spin_lock_irqsave(&mmu_rb_lock, flags); - list_del(&handler->list); - spin_unlock_irqrestore(&mmu_rb_lock, flags); + spin_lock(&mmu_rb_lock); + list_del_rcu(&handler->list); + spin_unlock(&mmu_rb_lock); + synchronize_rcu(); spin_lock_irqsave(&handler->lock, flags); if (!RB_EMPTY_ROOT(root)) { @@ -271,16 +272,15 @@ void hfi1_mmu_rb_remove(struct rb_root *root, struct mmu_rb_node *node) static struct mmu_rb_handler *find_mmu_handler(struct rb_root *root) { struct mmu_rb_handler *handler; - unsigned long flags; - spin_lock_irqsave(&mmu_rb_lock, flags); - list_for_each_entry(handler, &mmu_rb_handlers, list) { + rcu_read_lock(); + list_for_each_entry_rcu(handler, &mmu_rb_handlers, list) { if (handler->root == root) goto unlock; } handler = NULL; unlock: - spin_unlock_irqrestore(&mmu_rb_lock, flags); + rcu_read_unlock(); return handler; } -- cgit v1.2.3-59-g8ed1b