Re: [RFC 5/5] security: smack: add kmem_cache for smack_master_listallocations

From: Casey Schaufler
Date: Sat Jun 15 2013 - 16:08:16 EST


On 6/13/2013 8:29 AM, Tomasz Stanislawski wrote:
> On ARM, sizeof(struct smack_master_list) == 12. Allocation by kmalloc() uses a
> 32-byte-long chunk to allocate 12 bytes. Just ask ksize(). It means that 63%
> of memory is simply wasted for padding bytes.
>
> The problem is fixed in this patch by using kmem_cache. The cache allocates
> struct smack_master_list using 16-byte-long chunks according to ksize(). This
> reduces amount of used memory by 50%.

As with patch 4, I need to see performance numbers. Saving 50%
is good, but if there are 20,000 rules you're only saving 320K
of memory.

>
> Signed-off-by: Tomasz Stanislawski <t.stanislaws@xxxxxxxxxxx>
> ---
> security/smack/smack.h | 7 +++++++
> security/smack/smack_lsm.c | 8 ++++++++
> security/smack/smackfs.c | 8 ++------
> 3 files changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/security/smack/smack.h b/security/smack/smack.h
> index 38ba673..463f818 100644
> --- a/security/smack/smack.h
> +++ b/security/smack/smack.h
> @@ -194,6 +194,12 @@ struct smk_audit_info {
> struct smack_audit_data sad;
> #endif
> };
> +
> +struct smack_master_list {
> + struct list_head list;
> + struct smack_rule *smk_rule;
> +};
> +
> /*
> * These functions are in smack_lsm.c
> */
> @@ -235,6 +241,7 @@ extern struct list_head smk_netlbladdr_list;
>
> /* Cache for fast and thrifty allocations */
> extern struct kmem_cache *smack_rule_cache;
> +extern struct kmem_cache *smack_master_list_cache;
>
> extern struct security_operations smack_ops;
>
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 7aa696a..1d4a1b0 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -3566,6 +3566,7 @@ static __init void init_smack_known_list(void)
>
> /* KMEM caches for fast and thrifty allocations */
> struct kmem_cache *smack_rule_cache;
> +struct kmem_cache *smack_master_list_cache;
>
> /**
> * smack_init - initialize the smack system
> @@ -3584,9 +3585,16 @@ static __init int smack_init(void)
> if (!smack_rule_cache)
> return -ENOMEM;
>
> + smack_master_list_cache = KMEM_CACHE(smack_master_list, 0);
> + if (!smack_master_list_cache) {
> + kmem_cache_destroy(smack_rule_cache);
> + return -ENOMEM;
> + }
> +
> tsp = new_task_smack(smack_known_floor.smk_known,
> smack_known_floor.smk_known, GFP_KERNEL);
> if (tsp == NULL) {
> + kmem_cache_destroy(smack_master_list_cache);
> kmem_cache_destroy(smack_rule_cache);
> return -ENOMEM;
> }
> diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
> index c08b1ec..c7a1b0d 100644
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -104,11 +104,6 @@ LIST_HEAD(smk_netlbladdr_list);
> * Rule lists are maintained for each label.
> * This master list is just for reading /smack/load and /smack/load2.
> */
> -struct smack_master_list {
> - struct list_head list;
> - struct smack_rule *smk_rule;
> -};
> -
> LIST_HEAD(smack_rule_list);
>
> struct smack_parsed_rule {
> @@ -233,7 +228,8 @@ static int smk_set_access(struct smack_parsed_rule *srp,
> * it needs to get added for reporting.
> */
> if (global) {
> - smlp = kzalloc(sizeof(*smlp), GFP_KERNEL);
> + smlp = kmem_cache_zalloc(smack_master_list_cache,
> + GFP_KERNEL);
> if (smlp != NULL) {
> smlp->smk_rule = sp;
> list_add_rcu(&smlp->list, &smack_rule_list);

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