Commit 67caea1f authored by Mitko Haralanov's avatar Mitko Haralanov Committed by Doug Ledford
Browse files

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: default avatarDean Luick <dean.luick@intel.com>
Reviewed-by: default avatarMike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: default avatarMitko Haralanov <mitko.haralanov@intel.com>
Signed-off-by: default avatarDoug Ledford <dledford@redhat.com>
parent b96b0404

drivers/staging/rdma/hfi1/mmu_rb.c

+11 −11
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ 
 *

 */

#include <linux/list.h>

#include <linux/rculist.h>

#include <linux/mmu_notifier.h>

#include <linux/interval_tree_generic.h>
@@ -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;

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE