Add infrastructure for resizable hash tables based on hlist_bl
which we will use in followup patches.
The tables allow RCU lookups during resizing, bucket modifications
are protected with per-bucket bit lock and additional custom locking,
the tables are resized when load reaches thresholds determined based
on load factor parameter.
Signed-off-by: Julian Anastasov <ja@xxxxxx>
---
include/net/ip_vs.h | 197 ++++++++++++++++++++++++++++++++
net/netfilter/ipvs/ip_vs_conn.c | 5 -
net/netfilter/ipvs/ip_vs_core.c | 175 ++++++++++++++++++++++++++++
3 files changed, 372 insertions(+), 5 deletions(-)
diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index 6b9b32257e10..51adba5f1bb9 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -11,6 +11,7 @@
#include <asm/types.h> /* for __uXX types */
#include <linux/list.h> /* for struct list_head */
+#include <linux/rculist_bl.h> /* for struct hlist_bl_head */
#include <linux/spinlock.h> /* for struct rwlock_t */
#include <linux/atomic.h> /* for struct atomic_t */
#include <linux/refcount.h> /* for struct refcount_t */
@@ -30,6 +31,7 @@
#endif
#include <net/net_namespace.h> /* Netw namespace */
#include <linux/sched/isolation.h>
+#include <linux/siphash.h>
#define IP_VS_HDR_INVERSE 1
#define IP_VS_HDR_ICMP 2
@@ -271,6 +273,10 @@ static inline const char *ip_vs_dbg_addr(int af, char *buf, size_t buf_len,
pr_err(msg, ##__VA_ARGS__); \
} while (0)
+struct ip_vs_aligned_lock {
+ spinlock_t l; /* Protect buckets */
+} ____cacheline_aligned_in_smp;
+
/* For arrays per family */
enum {
IP_VS_AF_INET,
@@ -484,6 +490,197 @@ struct ip_vs_est_kt_data {
int est_row; /* estimated row */
};
+/* IPVS resizable hash tables */
+struct ip_vs_rht {
+ struct hlist_bl_head *buckets;
+ struct ip_vs_rht __rcu *new_tbl; /* New/Same table */
+ seqcount_t *seqc; /* Protects moves */
+ struct ip_vs_aligned_lock *lock; /* Protect seqc */
+ int mask; /* Buckets mask */
+ int size; /* Buckets */
+ int seqc_mask; /* seqc mask */
+ int lock_mask; /* lock mask */
+ u32 table_id;
+ int u_thresh; /* upper threshold */
+ int l_thresh; /* lower threshold */
+ int lfactor; /* Load Factor (shift)*/
+ int bits; /* size = 1 << bits */
+ siphash_key_t hash_key;
+ struct rcu_head rcu_head;
+};
+
+/**
+ * ip_vs_rht_for_each_table() - Walk the hash tables
+ * @table: struct ip_vs_rht __rcu *table
+ * @t: current table, used as cursor, struct ip_vs_rht *var
+ * @p: previous table, temp struct ip_vs_rht *var
+ *
+ * Walk tables assuming others can not change the installed tables
+ */
+#define ip_vs_rht_for_each_table(table, t, p) \
+ for (p = NULL, t = rcu_dereference_protected(table, 1); \
+ t != p; \
+ p = t, t = rcu_dereference_protected(t->new_tbl, 1))
+
+/**
+ * ip_vs_rht_for_each_table_rcu() - Walk the hash tables under RCU reader lock
+ * @table: struct ip_vs_rht __rcu *table
+ * @t: current table, used as cursor, struct ip_vs_rht *var
+ * @p: previous table, temp struct ip_vs_rht *var
+ *
+ * We usually search in one table and also in second table on resizing
+ */
+#define ip_vs_rht_for_each_table_rcu(table, t, p) \
+ for (p = NULL, t = rcu_dereference(table); \
+ t != p; \
+ p = t, t = rcu_dereference(t->new_tbl))
+
+/**
+ * ip_vs_rht_for_each_bucket() - Walk all table buckets
+ * @t: current table, used as cursor, struct ip_vs_rht *var
+ * @bucket: bucket index, used as cursor, u32 var
+ * @head: bucket address, used as cursor, struct hlist_bl_head *var
+ */
+#define ip_vs_rht_for_each_bucket(t, bucket, head) \
+ for (bucket = 0, head = (t)->buckets; \
+ bucket < t->size; bucket++, head++)
+
+/**
+ * ip_vs_rht_for_bucket_retry() - Retry bucket if entries are moved
+ * @t: current table, used as cursor, struct ip_vs_rht *var
+ * @bucket: index of current bucket or hash key
+ * @sc: temp seqcount_t *var
+ * @retry: temp int var
+ */
+#define ip_vs_rht_for_bucket_retry(t, bucket, sc, seq, retry) \
+ for (retry = 1, sc = &(t)->seqc[(bucket) & (t)->seqc_mask]; \
+ retry && ({ seq = read_seqcount_begin(sc); 1; }); \
+ retry = read_seqcount_retry(sc, seq))
+
+/**
+ * DECLARE_IP_VS_RHT_WALK_BUCKETS_RCU() - Declare variables
+ *
+ * Variables for ip_vs_rht_walk_buckets_rcu
+ */
+#define DECLARE_IP_VS_RHT_WALK_BUCKETS_RCU() \
+ struct ip_vs_rht *_t, *_p; \
+ unsigned int _seq; \
+ seqcount_t *_sc; \
+ u32 _bucket; \
+ int _retry
+/**
+ * ip_vs_rht_walk_buckets_rcu() - Walk all buckets under RCU read lock
+ * @table: struct ip_vs_rht __rcu *table
+ * @head: bucket address, used as cursor, struct hlist_bl_head *var
+ *
+ * Can be used while others add/delete/move entries
+ * Not suitable if duplicates are not desired
+ * Possible cases for reader that uses cond_resched_rcu() in the loop:
+ * - new table can not be installed, no need to repeat
+ * - new table can be installed => check and repeat if new table is
+ * installed, needed for !PREEMPT_RCU
+ */
+#define ip_vs_rht_walk_buckets_rcu(table, head) \
+ ip_vs_rht_for_each_table_rcu(table, _t, _p) \
+ ip_vs_rht_for_each_bucket(_t, _bucket, head) \
+ ip_vs_rht_for_bucket_retry(_t, _bucket, _sc, \
+ _seq, _retry)
+
+/**
+ * DECLARE_IP_VS_RHT_WALK_BUCKET_RCU() - Declare variables
+ *
+ * Variables for ip_vs_rht_walk_bucket_rcu
+ */
+#define DECLARE_IP_VS_RHT_WALK_BUCKET_RCU() \
+ unsigned int _seq; \
+ seqcount_t *_sc; \
+ int _retry
+/**
+ * ip_vs_rht_walk_bucket_rcu() - Walk bucket under RCU read lock
+ * @t: current table, struct ip_vs_rht *var
+ * @bucket: index of current bucket or hash key
+ * @head: bucket address, used as cursor, struct hlist_bl_head *var
+ *
+ * Can be used while others add/delete/move entries
+ * Not suitable if duplicates are not desired
+ * Possible cases for reader that uses cond_resched_rcu() in the loop:
+ * - new table can not be installed, no need to repeat
+ * - new table can be installed => check and repeat if new table is
+ * installed, needed for !PREEMPT_RCU
+ */
+#define ip_vs_rht_walk_bucket_rcu(t, bucket, head) \
+ if (({ head = (t)->buckets + ((bucket) & (t)->mask); 0; })) \
+ {} \
+ else \
+ ip_vs_rht_for_bucket_retry(t, (bucket), _sc, _seq, _retry)
+
+/**
+ * DECLARE_IP_VS_RHT_WALK_BUCKETS_SAFE_RCU() - Declare variables
+ *
+ * Variables for ip_vs_rht_walk_buckets_safe_rcu
+ */
+#define DECLARE_IP_VS_RHT_WALK_BUCKETS_SAFE_RCU() \
+ struct ip_vs_rht *_t, *_p; \
+ u32 _bucket
+/**
+ * ip_vs_rht_walk_buckets_safe_rcu() - Walk all buckets under RCU read lock
+ * @table: struct ip_vs_rht __rcu *table
+ * @head: bucket address, used as cursor, struct hlist_bl_head *var
+ *
+ * Can be used while others add/delete entries but moving is disabled
+ * Using cond_resched_rcu() should be safe if tables do not change
+ */
+#define ip_vs_rht_walk_buckets_safe_rcu(table, head) \
+ ip_vs_rht_for_each_table_rcu(table, _t, _p) \
+ ip_vs_rht_for_each_bucket(_t, _bucket, head)
+
+/**
+ * DECLARE_IP_VS_RHT_WALK_BUCKETS() - Declare variables
+ *
+ * Variables for ip_vs_rht_walk_buckets
+ */
+#define DECLARE_IP_VS_RHT_WALK_BUCKETS() \
+ struct ip_vs_rht *_t, *_p; \
+ u32 _bucket
+
+/**
+ * ip_vs_rht_walk_buckets() - Walk all buckets
+ * @table: struct ip_vs_rht __rcu *table
+ * @head: bucket address, used as cursor, struct hlist_bl_head *var
+ *
+ * Use if others can not add/delete/move entries
+ */
+#define ip_vs_rht_walk_buckets(table, head) \
+ ip_vs_rht_for_each_table(table, _t, _p) \
+ ip_vs_rht_for_each_bucket(_t, _bucket, head)
+
+/* Entries can be in one of two tables, so we flip bit when new table is
+ * created and store it as highest bit in hash keys
+ */
+#define IP_VS_RHT_TABLE_ID_MASK BIT(31)
+
+/* Check if hash key is from this table */
+static inline bool ip_vs_rht_same_table(struct ip_vs_rht *t, u32 hash_key)
+{
+ return !((t->table_id ^ hash_key) & IP_VS_RHT_TABLE_ID_MASK);
+}
+
+/* Build per-table hash key from hash value */
+static inline u32 ip_vs_rht_build_hash_key(struct ip_vs_rht *t, u32 hash)
+{
+ return t->table_id | (hash & ~IP_VS_RHT_TABLE_ID_MASK);
+}
+
+void ip_vs_rht_free(struct ip_vs_rht *t);
+void ip_vs_rht_rcu_free(struct rcu_head *head);
+struct ip_vs_rht *ip_vs_rht_alloc(int buckets, int scounts, int locks);
+int ip_vs_rht_desired_size(struct netns_ipvs *ipvs, struct ip_vs_rht *t, int n,
+ int lfactor, int min_bits, int max_bits);
+void ip_vs_rht_set_thresholds(struct ip_vs_rht *t, int size, int lfactor,
+ int min_bits, int max_bits);
+u32 ip_vs_rht_hash_linfo(struct ip_vs_rht *t, int af,
+ const union nf_inet_addr *addr, u32 v1, u32 v2);
+
struct dst_entry;
struct iphdr;
struct ip_vs_conn;
diff --git a/net/netfilter/ipvs/ip_vs_conn.c b/net/netfilter/ipvs/ip_vs_conn.c
index 98d7dbe3d787..a24af0ea59eb 100644
--- a/net/netfilter/ipvs/ip_vs_conn.c
+++ b/net/netfilter/ipvs/ip_vs_conn.c
@@ -80,11 +80,6 @@ static unsigned int ip_vs_conn_rnd __read_mostly;
#define IP_VS_ADDRSTRLEN (8+1)
#endif
-struct ip_vs_aligned_lock
-{
- spinlock_t l;
-} __attribute__((__aligned__(SMP_CACHE_BYTES)));
-
/* lock array for conn table */
static struct ip_vs_aligned_lock
__ip_vs_conntbl_lock_array[CT_LOCKARRAY_SIZE] __cacheline_aligned;
diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
index 141da3c14f57..884c2e143a17 100644
--- a/net/netfilter/ipvs/ip_vs_core.c
+++ b/net/netfilter/ipvs/ip_vs_core.c
@@ -118,6 +118,181 @@ void ip_vs_init_hash_table(struct list_head *table, int rows)
INIT_LIST_HEAD(&table[rows]);
}
+/* IPVS Resizable Hash Tables:
+ * - list_bl buckets with bit lock
+ *
+ * Goals:
+ * - RCU lookup for entry can run in parallel with add/del/move operations
+ * - resizing can trigger on load change or depending on key refresh period
+ * - add/del/move operations should be allowed for any context
+ *
+ * Resizing:
+ * - new table is attached to the current table and all entries are moved
+ * with new hash key. Finally, the new table is installed as current one and
+ * the old table is released after RCU grace period.
+ * - RCU read-side critical sections will walk two tables while resizing is
+ * in progress
+ * - new entries are added to the new table
+ * - entries will be deleted from the old or from the new table, the table_id
+ * can be saved into entry as part of the hash key to know where the entry is
+ * hashed
+ * - move operations may delay readers or to cause retry for the modified
+ * bucket. As result, searched entry will be found but walkers that operate
+ * on multiple entries may see same entry twice if bucket walking is retried.
+ * - for fast path the number of entries (load) can be compared to u_thresh
+ * and l_thresh to decide when to trigger table growing/shrinking. They
+ * are calculated based on load factor (shift count), negative value allows
+ * load to be below 100% to reduce collisions by maintaining larger table
+ * while positive value tolerates collisions by using smaller table and load
+ * above 100%: u_thresh(load) = size * (2 ^ lfactor)
+ *
+ * Locking:
+ * - lock: protect seqc if other context except resizer can move entries
+ * - seqc: seqcount_t, delay/retry readers while entries are moved to
+ * new table on resizing
+ * - bit lock: serialize bucket modifications
+ * - writers may use other locking mechanisms to serialize operations for
+ * resizing, moving and installing new tables
+ */
+
+void ip_vs_rht_free(struct ip_vs_rht *t)
+{
+ kvfree(t->buckets);
+ kvfree(t->seqc);
+ kvfree(t->lock);
+ kfree(t);
+}
+
+void ip_vs_rht_rcu_free(struct rcu_head *head)
+{
+ struct ip_vs_rht *t;
+
+ t = container_of(head, struct ip_vs_rht, rcu_head);
+ ip_vs_rht_free(t);
+}
+
+struct ip_vs_rht *ip_vs_rht_alloc(int buckets, int scounts, int locks)
+{
+ struct ip_vs_rht *t = kzalloc(sizeof(*t), GFP_KERNEL);
+ int i;
+
+ if (!t)
+ return NULL;
+ if (scounts) {
+ int ml = roundup_pow_of_two(nr_cpu_ids);
+
+ scounts = min(scounts, buckets);
+ scounts = min(scounts, ml);
+ t->seqc = kvmalloc_array(scounts, sizeof(*t->seqc), GFP_KERNEL);
+ if (!t->seqc)
+ goto err;
+ for (i = 0; i < scounts; i++)
+ seqcount_init(&t->seqc[i]);
+
+ if (locks) {
+ locks = min(locks, scounts);
+ t->lock = kvmalloc_array(locks, sizeof(*t->lock),
+ GFP_KERNEL);
+ if (!t->lock)
+ goto err;
+ for (i = 0; i < locks; i++)
+ spin_lock_init(&t->lock[i].l);
+ }
+ }
+
+ t->buckets = kvmalloc_array(buckets, sizeof(*t->buckets), GFP_KERNEL);
+ if (!t->buckets)
+ goto err;
+ for (i = 0; i < buckets; i++)
+ INIT_HLIST_BL_HEAD(&t->buckets[i]);
+ t->mask = buckets - 1;
+ t->size = buckets;
+ t->seqc_mask = scounts - 1;
+ t->lock_mask = locks - 1;
+ t->u_thresh = buckets;
+ t->l_thresh = buckets >> 4;
+ t->bits = order_base_2(buckets);
+ /* new_tbl points to self if no new table is filled */
+ RCU_INIT_POINTER(t->new_tbl, t);
+ get_random_bytes(&t->hash_key, sizeof(t->hash_key));
+ return t;
+
+err:
+ ip_vs_rht_free(t);
+ return NULL;
+}
+
+/* Get the desired table size for n entries based on current table size and
+ * by using the formula size = n / (2^lfactor)
+ * lfactor: shift value for the load factor:
+ * - >0: u_thresh=size << lfactor, for load factor above 100%
+ * - <0: u_thresh=size >> -lfactor, for load factor below 100%
+ * - 0: for load factor of 100%
+ */
+int ip_vs_rht_desired_size(struct netns_ipvs *ipvs, struct ip_vs_rht *t, int n,
+ int lfactor, int min_bits, int max_bits)
+{
+ if (!t)
+ return 1 << min_bits;
+ n = roundup_pow_of_two(n);
+ if (lfactor < 0) {
+ int factor = min(-lfactor, max_bits);
+
+ n = min(n, 1 << (max_bits - factor));
+ n <<= factor;
+ } else {
+ n = min(n >> lfactor, 1 << max_bits);
+ }
+ if (lfactor != t->lfactor)
+ return clamp(n, 1 << min_bits, 1 << max_bits);
+ if (n > t->size)
+ return n;
+ if (n > t->size >> 4)
+ return t->size;
+ /* Shrink but keep it n * 2 to prevent frequent resizing */
+ return clamp(n << 1, 1 << min_bits, 1 << max_bits);
+}
+
+/* Set thresholds based on table size and load factor:
+ * u_thresh = size * (2^lfactor)
+ * l_thresh = u_thresh / 16
+ * u_thresh/l_thresh can be used to check if load triggers a table grow/shrink
+ */
+void ip_vs_rht_set_thresholds(struct ip_vs_rht *t, int size, int lfactor,
+ int min_bits, int max_bits)
+{
+ if (size >= 1 << max_bits)
+ t->u_thresh = INT_MAX; /* stop growing */
+ else if (lfactor <= 0)
+ t->u_thresh = size >> min(-lfactor, max_bits);
+ else
+ t->u_thresh = min(size, 1 << (30 - lfactor)) << lfactor;
+
+ /* l_thresh: shrink when load is 16 times lower, can be 0 */
+ if (size >= 1 << max_bits)
+ t->l_thresh = (1 << max_bits) >> 4;
+ else if (size > 1 << min_bits)
+ t->l_thresh = t->u_thresh >> 4;
+ else
+ t->l_thresh = 0; /* stop shrinking */
+}
+
+/* Return hash value for local info (fast, insecure) */
+u32 ip_vs_rht_hash_linfo(struct ip_vs_rht *t, int af,
+ const union nf_inet_addr *addr, u32 v1, u32 v2)
+{
+ u32 v3;
+
+#ifdef CONFIG_IP_VS_IPV6
+ if (af == AF_INET6)
+ v3 = ipv6_addr_hash(&addr->in6);
+ else
+#endif
+ v3 = addr->all[0];
+
+ return jhash_3words(v1, v2, v3, (u32)t->hash_key.key[0]);
+}
+
static inline void
ip_vs_in_stats(struct ip_vs_conn *cp, struct sk_buff *skb)
{
--
2.44.0
