Commit 866694af authored by Patrick Kelsey's avatar Patrick Kelsey Committed by Leon Romanovsky
Browse files

IB/hfi1: Place struct mmu_rb_handler on cache line start 



Place struct mmu_rb_handler on cache line start like so:

	struct mmu_rb_handler *h;
	void *free_ptr;
	int ret;

	free_ptr = kzalloc(sizeof(*h) + cache_line_size() - 1, GFP_KERNEL);
	if (!free_ptr)
		return -ENOMEM;

	h = PTR_ALIGN(free_ptr, cache_line_size());

Additionally, move struct mmu_rb_handler fields "root" and "ops_args" to
start after the next cacheline using the "____cacheline_aligned_in_smp"
annotation.

Allocating an additional cache_line_size() - 1 bytes to place
struct mmu_rb_handler on a cache line start does increase memory
consumption.

However, few struct mmu_rb_handler are created when hfi1 is in use.
As mmu_rb_handler->root and mmu_rb_handler->ops_args are accessed
frequently, the advantage of having them both within a cache line is
expected to outweigh the disadvantage of the additional memory
consumption per struct mmu_rb_handler.

Signed-off-by: default avatarBrendan Cunningham <bcunningham@cornelisnetworks.com>
Signed-off-by: default avatarPatrick Kelsey <pat.kelsey@cornelisnetworks.com>
Signed-off-by: default avatarDennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Link: https://lore.kernel.org/r/168088636963.3027109.16959757980497822530.stgit@252.162.96.66.static.eigbox.net


Signed-off-by: default avatarLeon Romanovsky <leon@kernel.org>
parent 00cbce5c

drivers/infiniband/hw/hfi1/mmu_rb.c

+7 −4
Original line number Diff line number Diff line
@@ -46,12 +46,14 @@ int hfi1_mmu_rb_register(void *ops_arg, 
			 struct mmu_rb_handler **handler)

{

	struct mmu_rb_handler *h;

	void *free_ptr;

	int ret;



	h = kzalloc(sizeof(*h), GFP_KERNEL);

	if (!h)

	free_ptr = kzalloc(sizeof(*h) + cache_line_size() - 1, GFP_KERNEL);

	if (!free_ptr)

		return -ENOMEM;



	h = PTR_ALIGN(free_ptr, cache_line_size());

	h->root = RB_ROOT_CACHED;

	h->ops = ops;

	h->ops_arg = ops_arg;
@@ -62,10 +64,11 @@ int hfi1_mmu_rb_register(void *ops_arg, 
	INIT_LIST_HEAD(&h->del_list);

	INIT_LIST_HEAD(&h->lru_list);

	h->wq = wq;

	h->free_ptr = free_ptr;



	ret = mmu_notifier_register(&h->mn, current->mm);

	if (ret) {

		kfree(h);

		kfree(free_ptr);

		return ret;

	}
@@ -108,7 +111,7 @@ void hfi1_mmu_rb_unregister(struct mmu_rb_handler *handler) 
	/* Now the mm may be freed. */

	mmdrop(handler->mn.mm);



	kfree(handler);

	kfree(handler->free_ptr);

}



int hfi1_mmu_rb_insert(struct mmu_rb_handler *handler,

drivers/infiniband/hw/hfi1/mmu_rb.h

+12 −2
Original line number Diff line number Diff line
@@ -33,15 +33,25 @@ struct mmu_rb_ops { 
};



struct mmu_rb_handler {

	/*

	 * struct mmu_notifier is 56 bytes, and spinlock_t is 4 bytes, so

	 * they fit together in one cache line.  mn is relatively rarely

	 * accessed, so co-locating the spinlock with it achieves much of

	 * the cacheline contention reduction of giving the spinlock its own

	 * cacheline without the overhead of doing so.

	 */

	struct mmu_notifier mn;

	struct rb_root_cached root;

	void *ops_arg;

	spinlock_t lock;        /* protect the RB tree */



	/* Begin on a new cachline boundary here */

	struct rb_root_cached root ____cacheline_aligned_in_smp;

	void *ops_arg;

	struct mmu_rb_ops *ops;

	struct list_head lru_list;

	struct work_struct del_work;

	struct list_head del_list;

	struct workqueue_struct *wq;

	void *free_ptr;

};



int hfi1_mmu_rb_register(void *ops_arg,