The patch titled
user_ns: improve the user_ns on-the-slab packaging
has been added to the -mm tree. Its filename is
user_ns-improve-the-user_ns-on-the-slab-packaging.patch
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------------------------------------------------------
Subject: user_ns: improve the user_ns on-the-slab packaging
From: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Currently on 64-bit arch the user_namespace is 2096 and when being
kmalloc-ed it resides on a 4k slab wasting 2003 bytes.
If we allocate a separate cache for it and reduce the hash size from 128
to 64 chains the packaging becomes *much* better - the struct is 1072
bytes and the hole between is 98 bytes.
Signed-off-by: Pavel Emelyanov <xemul@xxxxxxxxxx>
Acked-by: Serge E. Hallyn <serge@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/user_namespace.h | 2 +-
kernel/user_namespace.c | 16 +++++++++++++---
2 files changed, 14 insertions(+), 4 deletions(-)
diff -puN include/linux/user_namespace.h~user_ns-improve-the-user_ns-on-the-slab-packaging include/linux/user_namespace.h
--- a/include/linux/user_namespace.h~user_ns-improve-the-user_ns-on-the-slab-packaging
+++ a/include/linux/user_namespace.h
@@ -6,7 +6,7 @@
#include <linux/sched.h>
#include <linux/err.h>
-#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 8)
+#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)
#define UIDHASH_SZ (1 << UIDHASH_BITS)
struct user_namespace {
diff -puN kernel/user_namespace.c~user_ns-improve-the-user_ns-on-the-slab-packaging kernel/user_namespace.c
--- a/kernel/user_namespace.c~user_ns-improve-the-user_ns-on-the-slab-packaging
+++ a/kernel/user_namespace.c
@@ -12,6 +12,8 @@
#include <linux/highuid.h>
#include <linux/cred.h>
+static struct kmem_cache *user_ns_cachep __read_mostly;
+
/*
* Create a new user namespace, deriving the creator from the user in the
* passed credentials, and replacing that user with the new root user for the
@@ -26,7 +28,7 @@ int create_user_ns(struct cred *new)
struct user_struct *root_user;
int n;
- ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
+ ns = kmem_cache_alloc(user_ns_cachep, GFP_KERNEL);
if (!ns)
return -ENOMEM;
@@ -38,7 +40,7 @@ int create_user_ns(struct cred *new)
/* Alloc new root user. */
root_user = alloc_uid(ns, 0);
if (!root_user) {
- kfree(ns);
+ kmem_cache_free(user_ns_cachep, ns);
return -ENOMEM;
}
@@ -71,7 +73,7 @@ static void free_user_ns_work(struct wor
struct user_namespace *ns =
container_of(work, struct user_namespace, destroyer);
free_uid(ns->creator);
- kfree(ns);
+ kmem_cache_free(user_ns_cachep, ns);
}
void free_user_ns(struct kref *kref)
@@ -126,3 +128,11 @@ gid_t user_ns_map_gid(struct user_namesp
/* No useful relationship so no mapping */
return overflowgid;
}
+
+static __init int user_namespaces_init(void)
+{
+ user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
+ return 0;
+}
+
+__initcall(user_namespaces_init);
_
Patches currently in -mm which might be from xemul@xxxxxxxxxxxxx are
linux-next.patch
user_ns-improve-the-user_ns-on-the-slab-packaging.patch
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