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 <[email protected]> --- diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index 8178156..faf4679 100644 --- a/include/linux/user_namespace.h +++ b/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 --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 2591583..8aafa80 100644 --- a/kernel/user_namespace.c +++ b/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 work_struct *work) 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_namespace *to, const struct cred *cred, gid_t /* 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); _______________________________________________ Containers mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list [email protected] https://openvz.org/mailman/listinfo/devel
