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IB/qib: RCU locking for MR validation
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Profiling indicates that MR validation locking is expensive.  The MR
table is largely read-only and is a suitable candidate for RCU locking.

The patch uses RCU locking during validation to eliminate one
lock/unlock during that validation.

Reviewed-by: Mike Heinz <[email protected]>
Signed-off-by: Mike Marciniszyn <[email protected]>
Signed-off-by: Roland Dreier <[email protected]>
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@mmarcini @rolandd
mmarcini authored and rolandd committed Jul 9, 2012
1 parent 6a82649 commit 8aac4cc
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Showing 4 changed files with 66 additions and 50 deletions.
98 changes: 51 additions & 47 deletions drivers/infiniband/hw/qib/qib_keys.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -40,8 +40,7 @@
*
* Returns 0 if successful, otherwise returns -errno.
*
* Increments mr reference count and sets published
* as required.
* Increments mr reference count as required.
*
* Sets the lkey field mr for non-dma regions.
*
Expand All @@ -60,10 +59,12 @@ int qib_alloc_lkey(struct qib_mregion *mr, int dma_region)

/* special case for dma_mr lkey == 0 */
if (dma_region) {
/* should the dma_mr be relative to the pd? */
if (!dev->dma_mr) {
struct qib_mregion *tmr;

tmr = rcu_dereference(dev->dma_mr);
if (!tmr) {
qib_get_mr(mr);
dev->dma_mr = mr;
rcu_assign_pointer(dev->dma_mr, mr);
mr->lkey_published = 1;
}
goto success;
Expand Down Expand Up @@ -93,7 +94,7 @@ int qib_alloc_lkey(struct qib_mregion *mr, int dma_region)
rkt->gen++;
}
qib_get_mr(mr);
rkt->table[r] = mr;
rcu_assign_pointer(rkt->table[r], mr);
mr->lkey_published = 1;
success:
spin_unlock_irqrestore(&rkt->lock, flags);
Expand All @@ -120,33 +121,30 @@ void qib_free_lkey(struct qib_mregion *mr)
spin_lock_irqsave(&rkt->lock, flags);
if (!mr->lkey_published)
goto out;
mr->lkey_published = 0;


spin_lock_irqsave(&dev->lk_table.lock, flags);
if (lkey == 0) {
if (dev->dma_mr && dev->dma_mr == mr) {
qib_put_mr(dev->dma_mr);
dev->dma_mr = NULL;
}
} else {
if (lkey == 0)
rcu_assign_pointer(dev->dma_mr, NULL);
else {
r = lkey >> (32 - ib_qib_lkey_table_size);
qib_put_mr(dev->dma_mr);
rkt->table[r] = NULL;
rcu_assign_pointer(rkt->table[r], NULL);
}
qib_put_mr(mr);
mr->lkey_published = 0;
out:
spin_unlock_irqrestore(&dev->lk_table.lock, flags);
spin_unlock_irqrestore(&rkt->lock, flags);
}

/**
* qib_lkey_ok - check IB SGE for validity and initialize
* @rkt: table containing lkey to check SGE against
* @pd: protection domain
* @isge: outgoing internal SGE
* @sge: SGE to check
* @acc: access flags
*
* Return 1 if valid and successful, otherwise returns 0.
*
* increments the reference count upon success
*
* Check the IB SGE for validity and initialize our internal version
* of it.
*/
Expand All @@ -156,43 +154,44 @@ int qib_lkey_ok(struct qib_lkey_table *rkt, struct qib_pd *pd,
struct qib_mregion *mr;
unsigned n, m;
size_t off;
unsigned long flags;

/*
* We use LKEY == zero for kernel virtual addresses
* (see qib_get_dma_mr and qib_dma.c).
*/
spin_lock_irqsave(&rkt->lock, flags);
rcu_read_lock();
if (sge->lkey == 0) {
struct qib_ibdev *dev = to_idev(pd->ibpd.device);

if (pd->user)
goto bail;
if (!dev->dma_mr)
mr = rcu_dereference(dev->dma_mr);
if (!mr)
goto bail;
if (unlikely(!atomic_inc_not_zero(&mr->refcount)))
goto bail;
qib_get_mr(dev->dma_mr);
spin_unlock_irqrestore(&rkt->lock, flags);
rcu_read_unlock();

isge->mr = dev->dma_mr;
isge->mr = mr;
isge->vaddr = (void *) sge->addr;
isge->length = sge->length;
isge->sge_length = sge->length;
isge->m = 0;
isge->n = 0;
goto ok;
}
mr = rkt->table[(sge->lkey >> (32 - ib_qib_lkey_table_size))];
if (unlikely(mr == NULL || mr->lkey != sge->lkey ||
mr->pd != &pd->ibpd))
mr = rcu_dereference(
rkt->table[(sge->lkey >> (32 - ib_qib_lkey_table_size))]);
if (unlikely(!mr || mr->lkey != sge->lkey || mr->pd != &pd->ibpd))
goto bail;

off = sge->addr - mr->user_base;
if (unlikely(sge->addr < mr->user_base ||
off + sge->length > mr->length ||
(mr->access_flags & acc) != acc))
if (unlikely(sge->addr < mr->iova || off + sge->length > mr->length ||
(mr->access_flags & acc) == 0))
goto bail;
qib_get_mr(mr);
spin_unlock_irqrestore(&rkt->lock, flags);
if (unlikely(!atomic_inc_not_zero(&mr->refcount)))
goto bail;
rcu_read_unlock();

off += mr->offset;
if (mr->page_shift) {
Expand Down Expand Up @@ -228,20 +227,22 @@ int qib_lkey_ok(struct qib_lkey_table *rkt, struct qib_pd *pd,
ok:
return 1;
bail:
spin_unlock_irqrestore(&rkt->lock, flags);
rcu_read_unlock();
return 0;
}

/**
* qib_rkey_ok - check the IB virtual address, length, and RKEY
* @dev: infiniband device
* @ss: SGE state
* @qp: qp for validation
* @sge: SGE state
* @len: length of data
* @vaddr: virtual address to place data
* @rkey: rkey to check
* @acc: access flags
*
* Return 1 if successful, otherwise 0.
*
* increments the reference count upon success
*/
int qib_rkey_ok(struct qib_qp *qp, struct qib_sge *sge,
u32 len, u64 vaddr, u32 rkey, int acc)
Expand All @@ -250,25 +251,26 @@ int qib_rkey_ok(struct qib_qp *qp, struct qib_sge *sge,
struct qib_mregion *mr;
unsigned n, m;
size_t off;
unsigned long flags;

/*
* We use RKEY == zero for kernel virtual addresses
* (see qib_get_dma_mr and qib_dma.c).
*/
spin_lock_irqsave(&rkt->lock, flags);
rcu_read_lock();
if (rkey == 0) {
struct qib_pd *pd = to_ipd(qp->ibqp.pd);
struct qib_ibdev *dev = to_idev(pd->ibpd.device);

if (pd->user)
goto bail;
if (!dev->dma_mr)
mr = rcu_dereference(dev->dma_mr);
if (!mr)
goto bail;
qib_get_mr(dev->dma_mr);
spin_unlock_irqrestore(&rkt->lock, flags);
if (unlikely(!atomic_inc_not_zero(&mr->refcount)))
goto bail;
rcu_read_unlock();

sge->mr = dev->dma_mr;
sge->mr = mr;
sge->vaddr = (void *) vaddr;
sge->length = len;
sge->sge_length = len;
Expand All @@ -277,16 +279,18 @@ int qib_rkey_ok(struct qib_qp *qp, struct qib_sge *sge,
goto ok;
}

mr = rkt->table[(rkey >> (32 - ib_qib_lkey_table_size))];
if (unlikely(mr == NULL || mr->lkey != rkey || qp->ibqp.pd != mr->pd))
mr = rcu_dereference(
rkt->table[(rkey >> (32 - ib_qib_lkey_table_size))]);
if (unlikely(!mr || mr->lkey != rkey || qp->ibqp.pd != mr->pd))
goto bail;

off = vaddr - mr->iova;
if (unlikely(vaddr < mr->iova || off + len > mr->length ||
(mr->access_flags & acc) == 0))
goto bail;
qib_get_mr(mr);
spin_unlock_irqrestore(&rkt->lock, flags);
if (unlikely(!atomic_inc_not_zero(&mr->refcount)))
goto bail;
rcu_read_unlock();

off += mr->offset;
if (mr->page_shift) {
Expand Down Expand Up @@ -322,7 +326,7 @@ int qib_rkey_ok(struct qib_qp *qp, struct qib_sge *sge,
ok:
return 1;
bail:
spin_unlock_irqrestore(&rkt->lock, flags);
rcu_read_unlock();
return 0;
}

Expand Down
7 changes: 7 additions & 0 deletions drivers/infiniband/hw/qib/qib_mr.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -527,3 +527,10 @@ int qib_dealloc_fmr(struct ib_fmr *ibfmr)
out:
return ret;
}

void mr_rcu_callback(struct rcu_head *list)
{
struct qib_mregion *mr = container_of(list, struct qib_mregion, list);

complete(&mr->comp);
}
4 changes: 3 additions & 1 deletion drivers/infiniband/hw/qib/qib_verbs.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2066,7 +2066,9 @@ int qib_register_ib_device(struct qib_devdata *dd)
ret = -ENOMEM;
goto err_lk;
}
memset(dev->lk_table.table, 0, lk_tab_size);
RCU_INIT_POINTER(dev->dma_mr, NULL);
for (i = 0; i < dev->lk_table.max; i++)
RCU_INIT_POINTER(dev->lk_table.table[i], NULL);
INIT_LIST_HEAD(&dev->pending_mmaps);
spin_lock_init(&dev->pending_lock);
dev->mmap_offset = PAGE_SIZE;
Expand Down
7 changes: 5 additions & 2 deletions drivers/infiniband/hw/qib/qib_verbs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -303,8 +303,9 @@ struct qib_mregion {
u32 max_segs; /* number of qib_segs in all the arrays */
u32 mapsz; /* size of the map array */
u8 page_shift; /* 0 - non unform/non powerof2 sizes */
u8 lkey_published; /* in global table */
u8 lkey_published; /* in global table */
struct completion comp; /* complete when refcount goes to zero */
struct rcu_head list;
atomic_t refcount;
struct qib_segarray *map[0]; /* the segments */
};
Expand Down Expand Up @@ -1022,10 +1023,12 @@ static inline void qib_get_mr(struct qib_mregion *mr)
atomic_inc(&mr->refcount);
}

void mr_rcu_callback(struct rcu_head *list);

static inline void qib_put_mr(struct qib_mregion *mr)
{
if (unlikely(atomic_dec_and_test(&mr->refcount)))
complete(&mr->comp);
call_rcu(&mr->list, mr_rcu_callback);
}

static inline void qib_put_ss(struct qib_sge_state *ss)
Expand Down

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