Messages in this thread | | | Date | Thu, 27 Jun 2013 14:11:24 -0700 | From | Casey Schaufler <> | Subject | Re: [RFCv2] security: smack: add a hash table to quicken smk_find_entry() |
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On 6/11/2013 5:55 AM, Tomasz Stanislawski wrote: > This patch adds a hash table to quicken searching of a smack label by its name. > > Basically, the patch improves performance of SMACK initialization. Parsing of > rules involves translation from a string to a smack_known (aka label) entity > which is done in smk_find_entry(). > > The current implementation of the function iterates over a global list of > smack_known resulting in O(N) complexity for smk_find_entry(). The total > complexity of SMACK initialization becomes O(rules * labels). Therefore it > scales quadratically with a complexity of a system. > > Applying the patch reduced the complexity of smk_find_entry() to O(1) as long > as number of label is in hundreds. If the number of labels is increased please > update SMACK_HASH_SLOTS constant defined in security/smack/smack.h. Introducing > the configuration of this constant with Kconfig or cmdline might be a good > idea. > > The size of the hash table was adjusted experimentally. The rule set used by > TIZEN contains circa 17K rules for 500 labels. The table above contains > results of SMACK initialization using 'time smackctl apply' bash command. > The 'Ref' is a kernel without this patch applied. The consecutive values > refers to value of SMACK_HASH_SLOTS. Every measurement was repeated three > times to reduce noise. > > | Ref | 1 | 2 | 4 | 8 | 16 | 32 | 64 | 128 | 256 | 512 > -------------------------------------------------------------------------------------------- > Run1 | 1.156 | 1.096 | 0.883 | 0.764 | 0.692 | 0.667 | 0.649 | 0.633 | 0.634 | 0.629 | 0.620 > Run2 | 1.156 | 1.111 | 0.885 | 0.764 | 0.694 | 0.661 | 0.649 | 0.651 | 0.634 | 0.638 | 0.623 > Run3 | 1.160 | 1.107 | 0.886 | 0.764 | 0.694 | 0.671 | 0.661 | 0.638 | 0.631 | 0.624 | 0.638 > AVG | 1.157 | 1.105 | 0.885 | 0.764 | 0.693 | 0.666 | 0.653 | 0.641 | 0.633 | 0.630 | 0.627 > > Surprisingly, a single hlist is slightly faster than a double-linked list. > The speed-up saturates near 64 slots. Therefore I chose value 128 to provide > some margin if more labels were used. > It looks that IO becomes a new bottleneck. > > Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
I will take this into my tree after changing SMACK_HASH_SLOTS to 16.
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
> --- > security/smack/smack.h | 5 +++++ > security/smack/smack_access.c | 30 +++++++++++++++++++++++++++--- > security/smack/smack_lsm.c | 12 ++++++------ > 3 files changed, 38 insertions(+), 9 deletions(-) > > diff --git a/security/smack/smack.h b/security/smack/smack.h > index 339614c..b1d9441 100644 > --- a/security/smack/smack.h > +++ b/security/smack/smack.h > @@ -53,6 +53,7 @@ > */ > struct smack_known { > struct list_head list; > + struct hlist_node smk_hashed; > char *smk_known; > u32 smk_secid; > struct netlbl_lsm_secattr smk_netlabel; /* on wire labels */ > @@ -222,6 +223,7 @@ char *smk_parse_smack(const char *string, int len); > int smk_netlbl_mls(int, char *, struct netlbl_lsm_secattr *, int); > char *smk_import(const char *, int); > struct smack_known *smk_import_entry(const char *, int); > +void smk_insert_entry(struct smack_known *skp); > struct smack_known *smk_find_entry(const char *); > u32 smack_to_secid(const char *); > > @@ -247,6 +249,9 @@ extern struct list_head smk_netlbladdr_list; > > extern struct security_operations smack_ops; > > +#define SMACK_HASH_SLOTS 128 > +extern struct hlist_head smack_known_hash[SMACK_HASH_SLOTS]; > + > /* > * Is the directory transmuting? > */ > diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c > index 6a0377f..b598c32 100644 > --- a/security/smack/smack_access.c > +++ b/security/smack/smack_access.c > @@ -325,6 +325,25 @@ void smack_log(char *subject_label, char *object_label, int request, > > DEFINE_MUTEX(smack_known_lock); > > +struct hlist_head smack_known_hash[SMACK_HASH_SLOTS]; > + > +/** > + * smk_insert_entry - insert a smack label into a hash map, > + * > + * this function must be called under smack_known_lock > + */ > +void smk_insert_entry(struct smack_known *skp) > +{ > + unsigned int hash; > + struct hlist_head *head; > + > + hash = full_name_hash(skp->smk_known, strlen(skp->smk_known)); > + head = &smack_known_hash[hash & (SMACK_HASH_SLOTS - 1)]; > + > + hlist_add_head_rcu(&skp->smk_hashed, head); > + list_add_rcu(&skp->list, &smack_known_list); > +} > + > /** > * smk_find_entry - find a label on the list, return the list entry > * @string: a text string that might be a Smack label > @@ -334,12 +353,17 @@ DEFINE_MUTEX(smack_known_lock); > */ > struct smack_known *smk_find_entry(const char *string) > { > + unsigned int hash; > + struct hlist_head *head; > + struct hlist_node *cursor; > struct smack_known *skp; > > - list_for_each_entry_rcu(skp, &smack_known_list, list) { > + hash = full_name_hash(string, strlen(string)); > + head = &smack_known_hash[hash & (SMACK_HASH_SLOTS - 1)]; > + > + hlist_for_each_entry_rcu(skp, cursor, head, smk_hashed) > if (strcmp(skp->smk_known, string) == 0) > return skp; > - } > > return NULL; > } > @@ -475,7 +499,7 @@ struct smack_known *smk_import_entry(const char *string, int len) > * Make sure that the entry is actually > * filled before putting it on the list. > */ > - list_add_rcu(&skp->list, &smack_known_list); > + smk_insert_entry(skp); > goto unlockout; > } > /* > diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c > index 6a08330..6cabca6 100644 > --- a/security/smack/smack_lsm.c > +++ b/security/smack/smack_lsm.c > @@ -3868,12 +3868,12 @@ static __init void init_smack_known_list(void) > /* > * Create the known labels list > */ > - list_add(&smack_known_huh.list, &smack_known_list); > - list_add(&smack_known_hat.list, &smack_known_list); > - list_add(&smack_known_star.list, &smack_known_list); > - list_add(&smack_known_floor.list, &smack_known_list); > - list_add(&smack_known_invalid.list, &smack_known_list); > - list_add(&smack_known_web.list, &smack_known_list); > + smk_insert_entry(&smack_known_huh); > + smk_insert_entry(&smack_known_hat); > + smk_insert_entry(&smack_known_star); > + smk_insert_entry(&smack_known_floor); > + smk_insert_entry(&smack_known_invalid); > + smk_insert_entry(&smack_known_web); > } > > /**
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