* [PATCH v4] hashtable: introduce a small and naive hashtable
@ 2012-09-09 12:52 Sasha Levin
2012-09-10 2:48 ` Mathieu Desnoyers
0 siblings, 1 reply; 3+ messages in thread
From: Sasha Levin @ 2012-09-09 12:52 UTC (permalink / raw)
To: torvalds
Cc: tj, linux-kernel, rostedt, ebiederm, josh, mathieu.desnoyers,
David.Laight, palves, rmallon, bfields, Sasha Levin
This hashtable implementation is using hlist buckets to provide a simple
hashtable to prevent it from getting reimplemented all over the kernel.
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
I'll send just the hashtable patch itself to avoid spamming a bunch of people until
it's stable again.
include/linux/hashtable.h | 183 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 183 insertions(+)
create mode 100644 include/linux/hashtable.h
diff --git a/include/linux/hashtable.h b/include/linux/hashtable.h
new file mode 100644
index 0000000..2d2fd14
--- /dev/null
+++ b/include/linux/hashtable.h
@@ -0,0 +1,183 @@
+/*
+ * Hash table implementation
+ * (C) 2012 Sasha Levin <levinsasha928@gmail.com>
+ */
+
+#ifndef _LINUX_HASHTABLE_H
+#define _LINUX_HASHTABLE_H
+
+#include <linux/list.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/hash.h>
+#include <linux/rculist.h>
+
+#define DEFINE_HASHTABLE(name, bits) \
+ struct hlist_head name[HASH_SIZE(bits)] = \
+ { [0 ... HASH_SIZE(bits) - 1] = HLIST_HEAD_INIT };
+
+#define DECLARE_HASHTABLE(name, bits) \
+ struct hlist_head name[1 << bits];
+
+#define HASH_SIZE(name) (1 << (HASH_BITS(name)))
+#define HASH_BITS(name) (ilog2(ARRAY_SIZE(name)))
+
+/* Use hash_32 when possible to allow for fast 32bit hashing in 64bit kernels. */
+#define hash_min(val, bits) ({ \
+ sizeof(val) <= 4 ? \
+ hash_32(val, bits) : \
+ hash_long(val, bits); \
+})
+
+/**
+ * hash_init - initialize a hash table
+ * @hashtable: hashtable to be initialized
+ *
+ * Calculates the size of the hashtable from the given parameter, otherwise
+ * same as hash_init_size.
+ */
+#define hash_init(hashtable) \
+({ \
+ int __i; \
+ \
+ for (__i = 0; __i < HASH_BITS(hashtable); __i++) \
+ INIT_HLIST_HEAD(hashtable + __i); \
+})
+
+/**
+ * hash_add - add an object to a hashtable
+ * @hashtable: hashtable to add to
+ * @node: the &struct hlist_node of the object to be added
+ * @key: the key of the object to be added
+ */
+#define hash_add(hashtable, node, key) \
+ hlist_add_head(node, &hashtable[hash_min(key, HASH_BITS(hashtable))]);
+
+/**
+ * hash_add_rcu - add an object to a rcu enabled hashtable
+ * @hashtable: hashtable to add to
+ * @node: the &struct hlist_node of the object to be added
+ * @key: the key of the object to be added
+ */
+#define hash_add_rcu(hashtable, node, key) \
+ hlist_add_head_rcu(node, &hashtable[hash_min(key, HASH_BITS(hashtable))]);
+
+/**
+ * hash_hashed - check whether an object is in any hashtable
+ * @node: the &struct hlist_node of the object to be checked
+ */
+#define hash_hashed(node) (!hlist_unhashed(node))
+
+/**
+ * hash_empty - check whether a hashtable is empty
+ * @hashtable: hashtable to check
+ */
+#define hash_empty(hashtable) \
+({ \
+ int __i; \
+ bool __ret = true; \
+ \
+ for (__i = 0; __i < HASH_SIZE(hashtable); __i++) \
+ if (!hlist_empty(&hashtable[__i])) \
+ __ret = false; \
+ \
+ __ret; \
+})
+
+/**
+ * hash_del - remove an object from a hashtable
+ * @node: &struct hlist_node of the object to remove
+ */
+static inline void hash_del(struct hlist_node *node)
+{
+ hlist_del_init(node);
+}
+
+/**
+ * hash_del_rcu - remove an object from a rcu enabled hashtable
+ * @node: &struct hlist_node of the object to remove
+ */
+static inline void hash_del_rcu(struct hlist_node *node)
+{
+ hlist_del_init_rcu(node);
+}
+
+/**
+ * hash_for_each - iterate over a hashtable
+ * @name: hashtable to iterate
+ * @bkt: integer to use as bucket loop cursor
+ * @node: the &struct list_head to use as a loop cursor for each entry
+ * @obj: the type * to use as a loop cursor for each entry
+ * @member: the name of the hlist_node within the struct
+ */
+#define hash_for_each(name, bkt, node, obj, member) \
+ for (bkt = 0, node = NULL; node == NULL && bkt < HASH_SIZE(name); bkt++)\
+ hlist_for_each_entry(obj, node, &name[bkt], member)
+
+/**
+ * hash_for_each_rcu - iterate over a rcu enabled hashtable
+ * @name: hashtable to iterate
+ * @bkt: integer to use as bucket loop cursor
+ * @node: the &struct list_head to use as a loop cursor for each entry
+ * @obj: the type * to use as a loop cursor for each entry
+ * @member: the name of the hlist_node within the struct
+ */
+#define hash_for_each_rcu(name, bkt, node, obj, member) \
+ for (bkt = 0, node = NULL; node == NULL && bkt < HASH_SIZE(name); bkt++)\
+ hlist_for_each_entry_rcu(obj, node, &name[bkt], member)
+
+/**
+ * hash_for_each_safe - iterate over a hashtable safe against removal of
+ * hash entry
+ * @name: hashtable to iterate
+ * @bkt: integer to use as bucket loop cursor
+ * @node: the &struct list_head to use as a loop cursor for each entry
+ * @tmp: a &struct used for temporary storage
+ * @obj: the type * to use as a loop cursor for each entry
+ * @member: the name of the hlist_node within the struct
+ */
+#define hash_for_each_safe(name, bkt, node, tmp, obj, member) \
+ for (bkt = 0, node = NULL; node == NULL && bkt < HASH_SIZE(name); bkt++)\
+ hlist_for_each_entry_safe(obj, node, tmp, &name[bkt], member)
+
+/**
+ * hash_for_each_possible - iterate over all possible objects hashing to the
+ * same bucket
+ * @name: hashtable to iterate
+ * @obj: the type * to use as a loop cursor for each entry
+ * @node: the &struct list_head to use as a loop cursor for each entry
+ * @member: the name of the hlist_node within the struct
+ * @key: the key of the objects to iterate over
+ */
+#define hash_for_each_possible(name, obj, node, member, key) \
+ hlist_for_each_entry(obj, node, &name[hash_min(key, HASH_BITS(name))], member)
+
+/**
+ * hash_for_each_possible_rcu - iterate over all possible objects hashing to the
+ * same bucket in an rcu enabled hashtable
+ * in a rcu enabled hashtable
+ * @name: hashtable to iterate
+ * @obj: the type * to use as a loop cursor for each entry
+ * @node: the &struct list_head to use as a loop cursor for each entry
+ * @member: the name of the hlist_node within the struct
+ * @key: the key of the objects to iterate over
+ */
+#define hash_for_each_possible_rcu(name, obj, node, member, key) \
+ hlist_for_each_entry_rcu(obj, node, &name[hash_min(key, HASH_BITS(name))], member)
+
+/**
+ * hash_for_each_possible_safe - iterate over all possible objects hashing to the
+ * same bucket safe against removals
+ * @name: hashtable to iterate
+ * @obj: the type * to use as a loop cursor for each entry
+ * @node: the &struct list_head to use as a loop cursor for each entry
+ * @tmp: a &struct used for temporary storage
+ * @member: the name of the hlist_node within the struct
+ * @key: the key of the objects to iterate over
+ */
+#define hash_for_each_possible_safe(name, obj, node, tmp, member, key) \
+ hlist_for_each_entry_safe(obj, node, tmp, \
+ &name[hash_min(key, HASH_BITS(name))], member)
+
+
+#endif
--
1.7.12
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v4] hashtable: introduce a small and naive hashtable
2012-09-09 12:52 [PATCH v4] hashtable: introduce a small and naive hashtable Sasha Levin
@ 2012-09-10 2:48 ` Mathieu Desnoyers
2012-09-10 12:18 ` Sasha Levin
0 siblings, 1 reply; 3+ messages in thread
From: Mathieu Desnoyers @ 2012-09-10 2:48 UTC (permalink / raw)
To: Sasha Levin
Cc: torvalds, tj, linux-kernel, rostedt, ebiederm, josh,
David.Laight, palves, rmallon, bfields
* Sasha Levin (levinsasha928@gmail.com) wrote:
> This hashtable implementation is using hlist buckets to provide a simple
> hashtable to prevent it from getting reimplemented all over the kernel.
>
> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
> ---
>
> I'll send just the hashtable patch itself to avoid spamming a bunch of people until
> it's stable again.
>
> include/linux/hashtable.h | 183 ++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 183 insertions(+)
> create mode 100644 include/linux/hashtable.h
>
> diff --git a/include/linux/hashtable.h b/include/linux/hashtable.h
> new file mode 100644
> index 0000000..2d2fd14
> --- /dev/null
> +++ b/include/linux/hashtable.h
> @@ -0,0 +1,183 @@
> +/*
> + * Hash table implementation
> + * (C) 2012 Sasha Levin <levinsasha928@gmail.com>
> + */
> +
> +#ifndef _LINUX_HASHTABLE_H
> +#define _LINUX_HASHTABLE_H
> +
> +#include <linux/list.h>
> +#include <linux/types.h>
> +#include <linux/kernel.h>
> +#include <linux/hash.h>
> +#include <linux/rculist.h>
> +
> +#define DEFINE_HASHTABLE(name, bits) \
> + struct hlist_head name[HASH_SIZE(bits)] = \
> + { [0 ... HASH_SIZE(bits) - 1] = HLIST_HEAD_INIT };
I think the final ";" should not be here.
> +
> +#define DECLARE_HASHTABLE(name, bits) \
> + struct hlist_head name[1 << bits];
Is the operator priority always OK here, or should we put bits between
parenthesis ?
The final ";" should not be here.
> +
> +#define HASH_SIZE(name) (1 << (HASH_BITS(name)))
Parenthesis around HASH_BITS(name) seem useless.
> +#define HASH_BITS(name) (ilog2(ARRAY_SIZE(name)))
Parenthesis around ilog2(ARRAY_SIZE(name)) seem useless too.
> +
> +/* Use hash_32 when possible to allow for fast 32bit hashing in 64bit kernels. */
> +#define hash_min(val, bits) ({ \
hash_init has a newline before ({, but not here. Please use a consistent
style.
> + sizeof(val) <= 4 ? \
> + hash_32(val, bits) : \
> + hash_long(val, bits); \
> +})
> +
> +/**
> + * hash_init - initialize a hash table
> + * @hashtable: hashtable to be initialized
> + *
> + * Calculates the size of the hashtable from the given parameter, otherwise
> + * same as hash_init_size.
> + */
> +#define hash_init(hashtable) \
> +({ \
> + int __i; \
> + \
> + for (__i = 0; __i < HASH_BITS(hashtable); __i++) \
> + INIT_HLIST_HEAD(hashtable + __i); \
I suspect that hashtable will be a pointer, and you use the "+" operator
to do an offset on this pointer. Any thought on using:
INIT_HLIST_HEAD(&hashtable[__i]);
instead ? It would provide the same result, but would ensure that the
user is indeed passing a pointer, and not an integer.
Also, why isn't it a static inline ? I'm probably missing something. If
there is a reason why it needs to stay a #define, please document it in
the comment.
> +})
> +
> +/**
> + * hash_add - add an object to a hashtable
> + * @hashtable: hashtable to add to
> + * @node: the &struct hlist_node of the object to be added
> + * @key: the key of the object to be added
> + */
> +#define hash_add(hashtable, node, key) \
> + hlist_add_head(node, &hashtable[hash_min(key, HASH_BITS(hashtable))]);
> +
> +/**
> + * hash_add_rcu - add an object to a rcu enabled hashtable
> + * @hashtable: hashtable to add to
> + * @node: the &struct hlist_node of the object to be added
> + * @key: the key of the object to be added
> + */
> +#define hash_add_rcu(hashtable, node, key) \
> + hlist_add_head_rcu(node, &hashtable[hash_min(key, HASH_BITS(hashtable))]);
> +
> +/**
> + * hash_hashed - check whether an object is in any hashtable
> + * @node: the &struct hlist_node of the object to be checked
> + */
> +#define hash_hashed(node) (!hlist_unhashed(node))
> +
> +/**
> + * hash_empty - check whether a hashtable is empty
> + * @hashtable: hashtable to check
> + */
> +#define hash_empty(hashtable) \
> +({ \
> + int __i; \
> + bool __ret = true; \
> + \
> + for (__i = 0; __i < HASH_SIZE(hashtable); __i++) \
> + if (!hlist_empty(&hashtable[__i])) \
> + __ret = false; \
> + \
> + __ret; \
Same question here about static inline instead of #define ?
Thanks,
Mathieu
> +})
> +
> +/**
> + * hash_del - remove an object from a hashtable
> + * @node: &struct hlist_node of the object to remove
> + */
> +static inline void hash_del(struct hlist_node *node)
> +{
> + hlist_del_init(node);
> +}
> +
> +/**
> + * hash_del_rcu - remove an object from a rcu enabled hashtable
> + * @node: &struct hlist_node of the object to remove
> + */
> +static inline void hash_del_rcu(struct hlist_node *node)
> +{
> + hlist_del_init_rcu(node);
> +}
> +
> +/**
> + * hash_for_each - iterate over a hashtable
> + * @name: hashtable to iterate
> + * @bkt: integer to use as bucket loop cursor
> + * @node: the &struct list_head to use as a loop cursor for each entry
> + * @obj: the type * to use as a loop cursor for each entry
> + * @member: the name of the hlist_node within the struct
> + */
> +#define hash_for_each(name, bkt, node, obj, member) \
> + for (bkt = 0, node = NULL; node == NULL && bkt < HASH_SIZE(name); bkt++)\
> + hlist_for_each_entry(obj, node, &name[bkt], member)
> +
> +/**
> + * hash_for_each_rcu - iterate over a rcu enabled hashtable
> + * @name: hashtable to iterate
> + * @bkt: integer to use as bucket loop cursor
> + * @node: the &struct list_head to use as a loop cursor for each entry
> + * @obj: the type * to use as a loop cursor for each entry
> + * @member: the name of the hlist_node within the struct
> + */
> +#define hash_for_each_rcu(name, bkt, node, obj, member) \
> + for (bkt = 0, node = NULL; node == NULL && bkt < HASH_SIZE(name); bkt++)\
> + hlist_for_each_entry_rcu(obj, node, &name[bkt], member)
> +
> +/**
> + * hash_for_each_safe - iterate over a hashtable safe against removal of
> + * hash entry
> + * @name: hashtable to iterate
> + * @bkt: integer to use as bucket loop cursor
> + * @node: the &struct list_head to use as a loop cursor for each entry
> + * @tmp: a &struct used for temporary storage
> + * @obj: the type * to use as a loop cursor for each entry
> + * @member: the name of the hlist_node within the struct
> + */
> +#define hash_for_each_safe(name, bkt, node, tmp, obj, member) \
> + for (bkt = 0, node = NULL; node == NULL && bkt < HASH_SIZE(name); bkt++)\
> + hlist_for_each_entry_safe(obj, node, tmp, &name[bkt], member)
> +
> +/**
> + * hash_for_each_possible - iterate over all possible objects hashing to the
> + * same bucket
> + * @name: hashtable to iterate
> + * @obj: the type * to use as a loop cursor for each entry
> + * @node: the &struct list_head to use as a loop cursor for each entry
> + * @member: the name of the hlist_node within the struct
> + * @key: the key of the objects to iterate over
> + */
> +#define hash_for_each_possible(name, obj, node, member, key) \
> + hlist_for_each_entry(obj, node, &name[hash_min(key, HASH_BITS(name))], member)
> +
> +/**
> + * hash_for_each_possible_rcu - iterate over all possible objects hashing to the
> + * same bucket in an rcu enabled hashtable
> + * in a rcu enabled hashtable
> + * @name: hashtable to iterate
> + * @obj: the type * to use as a loop cursor for each entry
> + * @node: the &struct list_head to use as a loop cursor for each entry
> + * @member: the name of the hlist_node within the struct
> + * @key: the key of the objects to iterate over
> + */
> +#define hash_for_each_possible_rcu(name, obj, node, member, key) \
> + hlist_for_each_entry_rcu(obj, node, &name[hash_min(key, HASH_BITS(name))], member)
> +
> +/**
> + * hash_for_each_possible_safe - iterate over all possible objects hashing to the
> + * same bucket safe against removals
> + * @name: hashtable to iterate
> + * @obj: the type * to use as a loop cursor for each entry
> + * @node: the &struct list_head to use as a loop cursor for each entry
> + * @tmp: a &struct used for temporary storage
> + * @member: the name of the hlist_node within the struct
> + * @key: the key of the objects to iterate over
> + */
> +#define hash_for_each_possible_safe(name, obj, node, tmp, member, key) \
> + hlist_for_each_entry_safe(obj, node, tmp, \
> + &name[hash_min(key, HASH_BITS(name))], member)
> +
> +
> +#endif
> --
> 1.7.12
>
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v4] hashtable: introduce a small and naive hashtable
2012-09-10 2:48 ` Mathieu Desnoyers
@ 2012-09-10 12:18 ` Sasha Levin
0 siblings, 0 replies; 3+ messages in thread
From: Sasha Levin @ 2012-09-10 12:18 UTC (permalink / raw)
To: Mathieu Desnoyers
Cc: torvalds, tj, linux-kernel, rostedt, ebiederm, josh,
David.Laight, palves, rmallon, bfields
On 09/10/2012 04:48 AM, Mathieu Desnoyers wrote:
> * Sasha Levin (levinsasha928@gmail.com) wrote:
>> +#define hash_init(hashtable) \
>> +({ \
>> + int __i; \
>> + \
>> + for (__i = 0; __i < HASH_BITS(hashtable); __i++) \
>> + INIT_HLIST_HEAD(hashtable + __i); \
>
> I suspect that hashtable will be a pointer, and you use the "+" operator
> to do an offset on this pointer. Any thought on using:
>
> INIT_HLIST_HEAD(&hashtable[__i]);
>
> instead ? It would provide the same result, but would ensure that the
> user is indeed passing a pointer, and not an integer.
It also looks nicer :)
> Also, why isn't it a static inline ? I'm probably missing something. If
> there is a reason why it needs to stay a #define, please document it in
> the comment.
It's a define because it needs to get the size of the hashtable.
I'll document that.
Thanks,
Sasha
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-09-10 2:48 ` Mathieu Desnoyers
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