diff options
| author | Tejun Heo | 2013-02-27 17:05:08 -0800 |
|---|---|---|
| committer | Linus Torvalds | 2013-02-27 19:10:21 -0800 |
| commit | 0ffc2a9c8072969253a20821c2c733a2cbb4c7c7 (patch) | |
| tree | ff6a9d270d4f0fa5c770837c6d9e5d5aac2637a7 /include | |
| parent | 54616283c2948812a44240858ced610e7cacbde1 (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 'include')
| -rw-r--r-- | include/linux/idr.h | 25 |
1 files changed, 24 insertions, 1 deletions
diff --git a/include/linux/idr.h b/include/linux/idr.h index 7b1c5c6f9a06..a6f38b5c34e4 100644 --- a/include/linux/idr.h +++ b/include/linux/idr.h @@ -37,6 +37,7 @@ struct idr_layer { }; struct idr { + struct idr_layer __rcu *hint; /* the last layer allocated from */ struct idr_layer __rcu *top; struct idr_layer *id_free; int layers; /* only valid w/o concurrent changes */ @@ -71,7 +72,7 @@ struct idr { * This is what we export. */ -void *idr_find(struct idr *idp, int id); +void *idr_find_slowpath(struct idr *idp, int id); int idr_pre_get(struct idr *idp, gfp_t gfp_mask); int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id); void idr_preload(gfp_t gfp_mask); @@ -97,6 +98,28 @@ static inline void idr_preload_end(void) } /** + * 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. + */ +static inline void *idr_find(struct idr *idr, int id) +{ + struct idr_layer *hint = rcu_dereference_raw(idr->hint); + + if (hint && (id & ~IDR_MASK) == hint->prefix) + return rcu_dereference_raw(hint->ary[id & IDR_MASK]); + + return idr_find_slowpath(idr, id); +} + +/** * idr_get_new - allocate new idr entry * @idp: idr handle * @ptr: pointer you want associated with the id |