The patch titled
Subject: idr: implement lookup hint
has been removed from the -mm tree. Its filename was
idr-implement-lookup-hint.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Tejun Heo <tj@xxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxxxx: always do slow path when hint is uninitialized]
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Sasha Levin <sasha.levin@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/idr.h | 25 ++++++++++++++++++++++++-
lib/idr.c | 38 ++++++++++++++++----------------------
2 files changed, 40 insertions(+), 23 deletions(-)
diff -puN include/linux/idr.h~idr-implement-lookup-hint include/linux/idr.h
--- a/include/linux/idr.h~idr-implement-lookup-hint
+++ a/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
diff -puN lib/idr.c~idr-implement-lookup-hint lib/idr.c
--- a/lib/idr.c~idr-implement-lookup-hint
+++ a/lib/idr.c
@@ -137,8 +137,10 @@ static void idr_layer_rcu_free(struct rc
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, v
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
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,
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
_
Patches currently in -mm which might be from tj@xxxxxxxxxx are
origin.patch
linux-next.patch
slub-correctly-bootstrap-boot-caches.patch
block-restore-proc-partitions-to-not-display-non-partitionable-removable-devices.patch
coredump-only-sigkill-should-interrupt-the-coredumping-task.patch
coredump-ensure-that-sigkill-always-kills-the-dumping-thread.patch
coredump-sanitize-the-setting-of-signal-group_exit_code.patch
coredump-factor-out-the-setting-of-pf_dumpcore.patch
freezer-do-not-send-a-fake-signal-to-a-pf_dumpcore-thread.patch
coredump-make-wait_for_dump_helpers-freezable.patch
nfsd-idr_destroy-no-longer-needs-idr_remove_all.patch
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