aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorMatthew Wilcox <mawilcox@microsoft.com>2017-11-30 13:45:11 -0500
committerMatthew Wilcox <mawilcox@microsoft.com>2018-02-06 16:41:29 -0500
commit6ce711f2750031d12cec91384ac5cfa0a485b60a (patch)
treed1d3b3754641b22e51cc0fdeecb02a0ac7b31b54
parentidr: Warn if old iterators see large IDs (diff)
downloadlinux-dev-6ce711f2750031d12cec91384ac5cfa0a485b60a.tar.xz
linux-dev-6ce711f2750031d12cec91384ac5cfa0a485b60a.zip
idr: Make 1-based IDRs more efficient
About 20% of the IDR users in the kernel want the allocated IDs to start at 1. The implementation currently searches all the way down the left hand side of the tree, finds no free ID other than ID 0, walks all the way back up, and then all the way down again. This patch 'rebases' the ID so we fill the entire radix tree, rather than leave a gap at 0. Chris Wilson says: "I did the quick hack of allocating index 0 of the idr and that eradicated idr_get_free() from being at the top of the profiles for the many-object stress tests. This improvement will be much appreciated." Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
-rw-r--r--include/linux/idr.h66
-rw-r--r--lib/idr.c70
-rw-r--r--tools/testing/radix-tree/idr-test.c7
3 files changed, 103 insertions, 40 deletions
diff --git a/include/linux/idr.h b/include/linux/idr.h
index 95a82cf2ed02..86b38df6e121 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -18,6 +18,7 @@
struct idr {
struct radix_tree_root idr_rt;
+ unsigned int idr_base;
unsigned int idr_next;
};
@@ -30,13 +31,21 @@ struct idr {
/* Set the IDR flag and the IDR_FREE tag */
#define IDR_RT_MARKER ((__force gfp_t)(3 << __GFP_BITS_SHIFT))
-#define IDR_INIT \
-{ \
- .idr_rt = RADIX_TREE_INIT(IDR_RT_MARKER) \
+#define IDR_INIT_BASE(base) { \
+ .idr_rt = RADIX_TREE_INIT(IDR_RT_MARKER), \
+ .idr_base = (base), \
+ .idr_next = 0, \
}
#define DEFINE_IDR(name) struct idr name = IDR_INIT
/**
+ * IDR_INIT() - Initialise an IDR.
+ *
+ * A freshly-initialised IDR contains no IDs.
+ */
+#define IDR_INIT IDR_INIT_BASE(0)
+
+/**
* idr_get_cursor - Return the current position of the cyclic allocator
* @idr: idr handle
*
@@ -81,10 +90,12 @@ static inline void idr_set_cursor(struct idr *idr, unsigned int val)
void idr_preload(gfp_t gfp_mask);
-int idr_alloc(struct idr *, void *, int start, int end, gfp_t);
-int __must_check idr_alloc_u32(struct idr *, void *ptr, u32 *nextid,
+int idr_alloc(struct idr *, void *ptr, int start, int end, gfp_t);
+int __must_check idr_alloc_u32(struct idr *, void *ptr, u32 *id,
unsigned long max, gfp_t);
-int idr_alloc_cyclic(struct idr *, void *entry, int start, int end, gfp_t);
+int idr_alloc_cyclic(struct idr *, void *ptr, int start, int end, gfp_t);
+void *idr_remove(struct idr *, unsigned long id);
+void *idr_find(const struct idr *, unsigned long id);
int idr_for_each(const struct idr *,
int (*fn)(int id, void *p, void *data), void *data);
void *idr_get_next(struct idr *, int *nextid);
@@ -92,15 +103,31 @@ void *idr_get_next_ul(struct idr *, unsigned long *nextid);
void *idr_replace(struct idr *, void *, unsigned long id);
void idr_destroy(struct idr *);
-static inline void *idr_remove(struct idr *idr, unsigned long id)
+/**
+ * idr_init_base() - Initialise an IDR.
+ * @idr: IDR handle.
+ * @base: The base value for the IDR.
+ *
+ * This variation of idr_init() creates an IDR which will allocate IDs
+ * starting at %base.
+ */
+static inline void idr_init_base(struct idr *idr, int base)
{
- return radix_tree_delete_item(&idr->idr_rt, id, NULL);
+ INIT_RADIX_TREE(&idr->idr_rt, IDR_RT_MARKER);
+ idr->idr_base = base;
+ idr->idr_next = 0;
}
+/**
+ * idr_init() - Initialise an IDR.
+ * @idr: IDR handle.
+ *
+ * Initialise a dynamically allocated IDR. To initialise a
+ * statically allocated IDR, use DEFINE_IDR().
+ */
static inline void idr_init(struct idr *idr)
{
- INIT_RADIX_TREE(&idr->idr_rt, IDR_RT_MARKER);
- idr->idr_next = 0;
+ idr_init_base(idr, 0);
}
static inline bool idr_is_empty(const struct idr *idr)
@@ -121,25 +148,6 @@ static inline void idr_preload_end(void)
}
/**
- * idr_find() - Return pointer for given ID.
- * @idr: IDR handle.
- * @id: Pointer ID.
- *
- * Looks up the pointer associated with this ID. A %NULL pointer may
- * indicate that @id is not allocated or that the %NULL pointer was
- * associated with this ID.
- *
- * This function can be called under rcu_read_lock(), given that the leaf
- * pointers lifetimes are correctly managed.
- *
- * Return: The pointer associated with this ID.
- */
-static inline void *idr_find(const struct idr *idr, unsigned long id)
-{
- return radix_tree_lookup(&idr->idr_rt, id);
-}
-
-/**
* idr_for_each_entry() - Iterate over an IDR's elements of a given type.
* @idr: IDR handle.
* @entry: The type * to use as cursor
diff --git a/lib/idr.c b/lib/idr.c
index b47055efceb0..c98d77fcf393 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -36,18 +36,21 @@ int idr_alloc_u32(struct idr *idr, void *ptr, u32 *nextid,
{
struct radix_tree_iter iter;
void __rcu **slot;
+ int base = idr->idr_base;
+ int id = *nextid;
if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
return -EINVAL;
if (WARN_ON_ONCE(!(idr->idr_rt.gfp_mask & ROOT_IS_IDR)))
idr->idr_rt.gfp_mask |= IDR_RT_MARKER;
- radix_tree_iter_init(&iter, *nextid);
- slot = idr_get_free(&idr->idr_rt, &iter, gfp, max);
+ id = (id < base) ? 0 : id - base;
+ radix_tree_iter_init(&iter, id);
+ slot = idr_get_free(&idr->idr_rt, &iter, gfp, max - base);
if (IS_ERR(slot))
return PTR_ERR(slot);
- *nextid = iter.index;
+ *nextid = iter.index + base;
/* there is a memory barrier inside radix_tree_iter_replace() */
radix_tree_iter_replace(&idr->idr_rt, &iter, slot, ptr);
radix_tree_iter_tag_clear(&idr->idr_rt, &iter, IDR_FREE);
@@ -136,6 +139,46 @@ int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
EXPORT_SYMBOL(idr_alloc_cyclic);
/**
+ * idr_remove() - Remove an ID from the IDR.
+ * @idr: IDR handle.
+ * @id: Pointer ID.
+ *
+ * Removes this ID from the IDR. If the ID was not previously in the IDR,
+ * this function returns %NULL.
+ *
+ * Since this function modifies the IDR, the caller should provide their
+ * own locking to ensure that concurrent modification of the same IDR is
+ * not possible.
+ *
+ * Return: The pointer formerly associated with this ID.
+ */
+void *idr_remove(struct idr *idr, unsigned long id)
+{
+ return radix_tree_delete_item(&idr->idr_rt, id - idr->idr_base, NULL);
+}
+EXPORT_SYMBOL_GPL(idr_remove);
+
+/**
+ * idr_find() - Return pointer for given ID.
+ * @idr: IDR handle.
+ * @id: Pointer ID.
+ *
+ * Looks up the pointer associated with this ID. A %NULL pointer may
+ * indicate that @id is not allocated or that the %NULL pointer was
+ * associated with this ID.
+ *
+ * This function can be called under rcu_read_lock(), given that the leaf
+ * pointers lifetimes are correctly managed.
+ *
+ * Return: The pointer associated with this ID.
+ */
+void *idr_find(const struct idr *idr, unsigned long id)
+{
+ return radix_tree_lookup(&idr->idr_rt, id - idr->idr_base);
+}
+EXPORT_SYMBOL_GPL(idr_find);
+
+/**
* idr_for_each() - Iterate through all stored pointers.
* @idr: IDR handle.
* @fn: Function to be called for each pointer.
@@ -157,13 +200,14 @@ int idr_for_each(const struct idr *idr,
{
struct radix_tree_iter iter;
void __rcu **slot;
+ int base = idr->idr_base;
radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) {
int ret;
if (WARN_ON_ONCE(iter.index > INT_MAX))
break;
- ret = fn(iter.index, rcu_dereference_raw(*slot), data);
+ ret = fn(iter.index + base, rcu_dereference_raw(*slot), data);
if (ret)
return ret;
}
@@ -186,15 +230,19 @@ void *idr_get_next(struct idr *idr, int *nextid)
{
struct radix_tree_iter iter;
void __rcu **slot;
+ int base = idr->idr_base;
+ int id = *nextid;
- slot = radix_tree_iter_find(&idr->idr_rt, &iter, *nextid);
+ id = (id < base) ? 0 : id - base;
+ slot = radix_tree_iter_find(&idr->idr_rt, &iter, id);
if (!slot)
return NULL;
+ id = iter.index + base;
- if (WARN_ON_ONCE(iter.index > INT_MAX))
+ if (WARN_ON_ONCE(id > INT_MAX))
return NULL;
- *nextid = iter.index;
+ *nextid = id;
return rcu_dereference_raw(*slot);
}
EXPORT_SYMBOL(idr_get_next);
@@ -213,12 +261,15 @@ void *idr_get_next_ul(struct idr *idr, unsigned long *nextid)
{
struct radix_tree_iter iter;
void __rcu **slot;
+ unsigned long base = idr->idr_base;
+ unsigned long id = *nextid;
- slot = radix_tree_iter_find(&idr->idr_rt, &iter, *nextid);
+ id = (id < base) ? 0 : id - base;
+ slot = radix_tree_iter_find(&idr->idr_rt, &iter, id);
if (!slot)
return NULL;
- *nextid = iter.index;
+ *nextid = iter.index + base;
return rcu_dereference_raw(*slot);
}
EXPORT_SYMBOL(idr_get_next_ul);
@@ -245,6 +296,7 @@ void *idr_replace(struct idr *idr, void *ptr, unsigned long id)
if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
return ERR_PTR(-EINVAL);
+ id -= idr->idr_base;
entry = __radix_tree_lookup(&idr->idr_rt, id, &node, &slot);
if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE))
diff --git a/tools/testing/radix-tree/idr-test.c b/tools/testing/radix-tree/idr-test.c
index 36437ade429c..44ef9eba5a7a 100644
--- a/tools/testing/radix-tree/idr-test.c
+++ b/tools/testing/radix-tree/idr-test.c
@@ -153,11 +153,12 @@ void idr_nowait_test(void)
idr_destroy(&idr);
}
-void idr_get_next_test(void)
+void idr_get_next_test(int base)
{
unsigned long i;
int nextid;
DEFINE_IDR(idr);
+ idr_init_base(&idr, base);
int indices[] = {4, 7, 9, 15, 65, 128, 1000, 99999, 0};
@@ -244,7 +245,9 @@ void idr_checks(void)
idr_alloc_test();
idr_null_test();
idr_nowait_test();
- idr_get_next_test();
+ idr_get_next_test(0);
+ idr_get_next_test(1);
+ idr_get_next_test(4);
}
/*