The patch titled
slob: implement RCU freeing
has been added to the -mm tree. Its filename is
slob-implement-rcu-freeing.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: slob: implement RCU freeing
From: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
The SLOB allocator should implement SLAB_DESTROY_BY_RCU correctly, because
even on UP, RCU freeing semantics are not equivalent to simply freeing
immediately. This also allows SLOB to be used on SMP.
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
Acked-by: Matt Mackall <mpm@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
init/Kconfig | 7 +-----
mm/slob.c | 52 ++++++++++++++++++++++++++++++++++++++++++-------
2 files changed, 47 insertions(+), 12 deletions(-)
diff -puN init/Kconfig~slob-implement-rcu-freeing init/Kconfig
--- a/init/Kconfig~slob-implement-rcu-freeing
+++ a/init/Kconfig
@@ -537,14 +537,11 @@ config SLUB
and has enhanced diagnostics.
config SLOB
-#
-# SLOB does not support SMP because SLAB_DESTROY_BY_RCU is unsupported
-#
- depends on EMBEDDED && !SMP && !SPARSEMEM
+ depends on EMBEDDED && !SPARSEMEM
bool "SLOB (Simple Allocator)"
help
SLOB replaces the SLAB allocator with a drastically simpler
- allocator. SLOB is more space efficient that SLAB but does not
+ allocator. SLOB is more space efficient than SLAB but does not
scale well (single lock for all operations) and is also highly
susceptible to fragmentation. SLUB can accomplish a higher object
density. It is usually better to use SLUB instead of SLOB.
diff -puN mm/slob.c~slob-implement-rcu-freeing mm/slob.c
--- a/mm/slob.c~slob-implement-rcu-freeing
+++ a/mm/slob.c
@@ -35,6 +35,7 @@
#include <linux/init.h>
#include <linux/module.h>
#include <linux/timer.h>
+#include <linux/rcupdate.h>
struct slob_block {
int units;
@@ -53,6 +54,16 @@ struct bigblock {
};
typedef struct bigblock bigblock_t;
+/*
+ * struct slob_rcu is inserted at the tail of allocated slob blocks, which
+ * were created with a SLAB_DESTROY_BY_RCU slab. slob_rcu is used to free
+ * the block using call_rcu.
+ */
+struct slob_rcu {
+ struct rcu_head head;
+ int size;
+};
+
static slob_t arena = { .next = &arena, .units = 1 };
static slob_t *slobfree = &arena;
static bigblock_t *bigblocks;
@@ -266,6 +277,7 @@ size_t ksize(const void *block)
struct kmem_cache {
unsigned int size, align;
+ unsigned long flags;
const char *name;
void (*ctor)(void *, struct kmem_cache *, unsigned long);
void (*dtor)(void *, struct kmem_cache *, unsigned long);
@@ -283,6 +295,12 @@ struct kmem_cache *kmem_cache_create(con
if (c) {
c->name = name;
c->size = size;
+ if (flags & SLAB_DESTROY_BY_RCU) {
+ BUG_ON(c->dtor);
+ /* leave room for rcu footer at the end of object */
+ c->size += sizeof(struct slob_rcu);
+ }
+ c->flags = flags;
c->ctor = ctor;
c->dtor = dtor;
/* ignore alignment unless it's forced */
@@ -328,15 +346,35 @@ void *kmem_cache_zalloc(struct kmem_cach
}
EXPORT_SYMBOL(kmem_cache_zalloc);
-void kmem_cache_free(struct kmem_cache *c, void *b)
+static void __kmem_cache_free(void *b, int size)
{
- if (c->dtor)
- c->dtor(b, c, 0);
-
- if (c->size < PAGE_SIZE)
- slob_free(b, c->size);
+ if (size < PAGE_SIZE)
+ slob_free(b, size);
else
- free_pages((unsigned long)b, get_order(c->size));
+ free_pages((unsigned long)b, get_order(size));
+}
+
+static void kmem_rcu_free(struct rcu_head *head)
+{
+ struct slob_rcu *slob_rcu = (struct slob_rcu *)head;
+ void *b = (void *)slob_rcu - (slob_rcu->size - sizeof(struct slob_rcu));
+
+ __kmem_cache_free(b, slob_rcu->size);
+}
+
+void kmem_cache_free(struct kmem_cache *c, void *b)
+{
+ if (unlikely(c->flags & SLAB_DESTROY_BY_RCU)) {
+ struct slob_rcu *slob_rcu;
+ slob_rcu = b + (c->size - sizeof(struct slob_rcu));
+ INIT_RCU_HEAD(&slob_rcu->head);
+ slob_rcu->size = c->size;
+ call_rcu(&slob_rcu->head, kmem_rcu_free);
+ } else {
+ if (c->dtor)
+ c->dtor(b, c, 0);
+ __kmem_cache_free(b, c->size);
+ }
}
EXPORT_SYMBOL(kmem_cache_free);
_
Patches currently in -mm which might be from nickpiggin@xxxxxxxxxxxx are
origin.patch
ia64-race-flushing-icache-in-do_no_page-path.patch
slob-implement-rcu-freeing.patch
lazy-freeing-of-memory-through-madv_free.patch
restore-madv_dontneed-to-its-original-linux-behaviour.patch
mm-merge-populate-and-nopage-into-fault-fixes-nonlinear-fix.patch
convert-hugetlbfs-to-use-vm_ops-fault.patch
only-allow-nonlinear-vmas-for-ram-backed-filesystems.patch
cpuset-remove-sched-domain-hooks-from-cpusets.patch
sched2-sched-domain-sysctl.patch
-
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