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authorTejun Heo <tj@kernel.org>2013-02-28 01:05:08 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2013-02-28 03:10:21 (GMT)
commit0ffc2a9c8072969253a20821c2c733a2cbb4c7c7 (patch)
treeff6a9d270d4f0fa5c770837c6d9e5d5aac2637a7 /lib/idr.c
parent54616283c2948812a44240858ced610e7cacbde1 (diff)
idr: implement lookup hint
While idr lookup isn't a particularly heavy operation, it still is too substantial to use in hot paths without worrying about the performance implications. With recent changes, each idr_layer covers 256 slots which should be enough to cover most use cases with single idr_layer making lookup hint very attractive. This patch adds idr->hint which points to the idr_layer which allocated an ID most recently and the fast path lookup becomes if (look up target's prefix matches that of the hinted layer) return hint->ary[ID's offset in the leaf layer]; which can be inlined. idr->hint is set to the leaf node on idr_fill_slot() and cleared from free_layer(). [andriy.shevchenko@linux.intel.com: always do slow path when hint is uninitialized] Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Sasha Levin <sasha.levin@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/idr.c')
-rw-r--r--lib/idr.c38
1 files changed, 16 insertions, 22 deletions
diff --git a/lib/idr.c b/lib/idr.c
index 5cd6029..1a30272 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -137,8 +137,10 @@ static void idr_layer_rcu_free(struct rcu_head *head)
kmem_cache_free(idr_layer_cache, layer);
}
-static inline void free_layer(struct idr_layer *p)
+static inline void free_layer(struct idr *idr, struct idr_layer *p)
{
+ if (idr->hint && idr->hint == p)
+ RCU_INIT_POINTER(idr->hint, NULL);
call_rcu(&p->rcu_head, idr_layer_rcu_free);
}
@@ -363,8 +365,12 @@ build_up:
* @id and @pa are from a successful allocation from idr_get_empty_slot().
* Install the user pointer @ptr and mark the slot full.
*/
-static void idr_fill_slot(void *ptr, int id, struct idr_layer **pa)
+static void idr_fill_slot(struct idr *idr, void *ptr, int id,
+ struct idr_layer **pa)
{
+ /* update hint used for lookup, cleared from free_layer() */
+ rcu_assign_pointer(idr->hint, pa[0]);
+
rcu_assign_pointer(pa[0]->ary[id & IDR_MASK], (struct idr_layer *)ptr);
pa[0]->count++;
idr_mark_full(pa, id);
@@ -397,7 +403,7 @@ int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
if (rv < 0)
return rv == -ENOMEM ? -EAGAIN : rv;
- idr_fill_slot(ptr, rv, pa);
+ idr_fill_slot(idp, ptr, rv, pa);
*id = rv;
return 0;
}
@@ -504,7 +510,7 @@ int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask)
if (unlikely(id > max))
return -ENOSPC;
- idr_fill_slot(ptr, id, pa);
+ idr_fill_slot(idr, ptr, id, pa);
return id;
}
EXPORT_SYMBOL_GPL(idr_alloc);
@@ -541,14 +547,14 @@ static void sub_remove(struct idr *idp, int shift, int id)
to_free = NULL;
while(*paa && ! --((**paa)->count)){
if (to_free)
- free_layer(to_free);
+ free_layer(idp, to_free);
to_free = **paa;
**paa-- = NULL;
}
if (!*paa)
idp->layers = 0;
if (to_free)
- free_layer(to_free);
+ free_layer(idp, to_free);
} else
idr_remove_warning(id);
}
@@ -581,7 +587,7 @@ void idr_remove(struct idr *idp, int id)
--idp->layers;
to_free->count = 0;
bitmap_clear(to_free->bitmap, 0, IDR_SIZE);
- free_layer(to_free);
+ free_layer(idp, to_free);
}
while (idp->id_free_cnt >= MAX_IDR_FREE) {
p = get_from_free_list(idp);
@@ -622,7 +628,7 @@ void __idr_remove_all(struct idr *idp)
/* Get the highest bit that the above add changed from 0->1. */
while (n < fls(id ^ bt_mask)) {
if (p)
- free_layer(p);
+ free_layer(idp, p);
n += IDR_BITS;
p = *--paa;
}
@@ -655,19 +661,7 @@ void idr_destroy(struct idr *idp)
}
EXPORT_SYMBOL(idr_destroy);
-/**
- * idr_find - return pointer for given id
- * @idp: idr handle
- * @id: lookup key
- *
- * Return the pointer given the id it has been registered with. A %NULL
- * return indicates that @id is not valid or you passed %NULL in
- * idr_get_new().
- *
- * This function can be called under rcu_read_lock(), given that the leaf
- * pointers lifetimes are correctly managed.
- */
-void *idr_find(struct idr *idp, int id)
+void *idr_find_slowpath(struct idr *idp, int id)
{
int n;
struct idr_layer *p;
@@ -691,7 +685,7 @@ void *idr_find(struct idr *idp, int id)
}
return((void *)p);
}
-EXPORT_SYMBOL(idr_find);
+EXPORT_SYMBOL(idr_find_slowpath);
/**
* idr_for_each - iterate through all stored pointers

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