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Date: Thu, 30 Jul 2020 13:07:26 +0800
From: Tonghao Zhang <xiangxia.m.yue@...il.com>
To: Eelco Chaudron <echaudro@...hat.com>
Cc: Linux Kernel Network Developers <netdev@...r.kernel.org>,
David Miller <davem@...emloft.net>,
ovs dev <dev@...nvswitch.org>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Pravin Shelar <pshelar@....org>,
Florian Westphal <fw@...len.de>
Subject: Re: [PATCH net-next v3 2/2] net: openvswitch: make masks cache size configurable
On Wed, Jul 29, 2020 at 9:27 PM Eelco Chaudron <echaudro@...hat.com> wrote:
>
> This patch makes the masks cache size configurable, or with
> a size of 0, disable it.
>
> Reviewed-by: Paolo Abeni <pabeni@...hat.com>
> Signed-off-by: Eelco Chaudron <echaudro@...hat.com>
> ---
> Changes in v3:
> - Use is_power_of_2() function
> - Use array_size() function
> - Fix remaining sparse errors
>
> Changes in v2:
> - Fix sparse warnings
> - Fix netlink policy items reported by Florian Westphal
>
> include/uapi/linux/openvswitch.h | 1
> net/openvswitch/datapath.c | 14 +++++
> net/openvswitch/flow_table.c | 97 +++++++++++++++++++++++++++++++++-----
> net/openvswitch/flow_table.h | 10 ++++
> 4 files changed, 108 insertions(+), 14 deletions(-)
>
> diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
> index 7cb76e5ca7cf..8300cc29dec8 100644
> --- a/include/uapi/linux/openvswitch.h
> +++ b/include/uapi/linux/openvswitch.h
> @@ -86,6 +86,7 @@ enum ovs_datapath_attr {
> OVS_DP_ATTR_MEGAFLOW_STATS, /* struct ovs_dp_megaflow_stats */
> OVS_DP_ATTR_USER_FEATURES, /* OVS_DP_F_* */
> OVS_DP_ATTR_PAD,
> + OVS_DP_ATTR_MASKS_CACHE_SIZE,
> __OVS_DP_ATTR_MAX
> };
>
> diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
> index a54df1fe3ec4..114b2ddb8037 100644
> --- a/net/openvswitch/datapath.c
> +++ b/net/openvswitch/datapath.c
> @@ -1498,6 +1498,7 @@ static size_t ovs_dp_cmd_msg_size(void)
> msgsize += nla_total_size_64bit(sizeof(struct ovs_dp_stats));
> msgsize += nla_total_size_64bit(sizeof(struct ovs_dp_megaflow_stats));
> msgsize += nla_total_size(sizeof(u32)); /* OVS_DP_ATTR_USER_FEATURES */
> + msgsize += nla_total_size(sizeof(u32)); /* OVS_DP_ATTR_MASKS_CACHE_SIZE */
>
> return msgsize;
> }
> @@ -1535,6 +1536,10 @@ static int ovs_dp_cmd_fill_info(struct datapath *dp, struct sk_buff *skb,
> if (nla_put_u32(skb, OVS_DP_ATTR_USER_FEATURES, dp->user_features))
> goto nla_put_failure;
>
> + if (nla_put_u32(skb, OVS_DP_ATTR_MASKS_CACHE_SIZE,
> + ovs_flow_tbl_masks_cache_size(&dp->table)))
> + goto nla_put_failure;
> +
> genlmsg_end(skb, ovs_header);
> return 0;
>
> @@ -1599,6 +1604,13 @@ static int ovs_dp_change(struct datapath *dp, struct nlattr *a[])
> #endif
> }
>
> + if (a[OVS_DP_ATTR_MASKS_CACHE_SIZE]) {
> + u32 cache_size;
> +
> + cache_size = nla_get_u32(a[OVS_DP_ATTR_MASKS_CACHE_SIZE]);
> + ovs_flow_tbl_masks_cache_resize(&dp->table, cache_size);
Do we should return error code, if we can't change the "mask_cache"
size ? for example, -EINVAL, -ENOMEM
> + }
> +
> dp->user_features = user_features;
>
> if (dp->user_features & OVS_DP_F_TC_RECIRC_SHARING)
> @@ -1894,6 +1906,8 @@ static const struct nla_policy datapath_policy[OVS_DP_ATTR_MAX + 1] = {
> [OVS_DP_ATTR_NAME] = { .type = NLA_NUL_STRING, .len = IFNAMSIZ - 1 },
> [OVS_DP_ATTR_UPCALL_PID] = { .type = NLA_U32 },
> [OVS_DP_ATTR_USER_FEATURES] = { .type = NLA_U32 },
> + [OVS_DP_ATTR_MASKS_CACHE_SIZE] = NLA_POLICY_RANGE(NLA_U32, 0,
> + PCPU_MIN_UNIT_SIZE / sizeof(struct mask_cache_entry)),
> };
>
> static const struct genl_ops dp_datapath_genl_ops[] = {
> diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c
> index a5912ea05352..5280aeeef628 100644
> --- a/net/openvswitch/flow_table.c
> +++ b/net/openvswitch/flow_table.c
> @@ -38,8 +38,8 @@
> #define MASK_ARRAY_SIZE_MIN 16
> #define REHASH_INTERVAL (10 * 60 * HZ)
>
> +#define MC_DEFAULT_HASH_ENTRIES 256
> #define MC_HASH_SHIFT 8
> -#define MC_HASH_ENTRIES (1u << MC_HASH_SHIFT)
> #define MC_HASH_SEGS ((sizeof(uint32_t) * 8) / MC_HASH_SHIFT)
>
> static struct kmem_cache *flow_cache;
> @@ -341,15 +341,75 @@ static void flow_mask_remove(struct flow_table *tbl, struct sw_flow_mask *mask)
> }
> }
>
> +static void __mask_cache_destroy(struct mask_cache *mc)
> +{
> + if (mc->mask_cache)
> + free_percpu(mc->mask_cache);
free_percpu the NULL is safe. we can remove the "if".
> + kfree(mc);
> +}
> +
> +static void mask_cache_rcu_cb(struct rcu_head *rcu)
> +{
> + struct mask_cache *mc = container_of(rcu, struct mask_cache, rcu);
> +
> + __mask_cache_destroy(mc);
> +}
> +
> +static struct mask_cache *tbl_mask_cache_alloc(u32 size)
> +{
> + struct mask_cache_entry __percpu *cache = NULL;
> + struct mask_cache *new;
> +
> + /* Only allow size to be 0, or a power of 2, and does not exceed
> + * percpu allocation size.
> + */
> + if ((!is_power_of_2(size) && size != 0) ||
> + (size * sizeof(struct mask_cache_entry)) > PCPU_MIN_UNIT_SIZE)
> + return NULL;
> + new = kzalloc(sizeof(*new), GFP_KERNEL);
> + if (!new)
> + return NULL;
> +
> + new->cache_size = size;
> + if (new->cache_size > 0) {
> + cache = __alloc_percpu(array_size(sizeof(struct mask_cache_entry),
> + new->cache_size),
> + __alignof__(struct mask_cache_entry));
> + if (!cache) {
> + kfree(new);
> + return NULL;
> + }
> + }
> +
> + new->mask_cache = cache;
> + return new;
> +}
> +
> +void ovs_flow_tbl_masks_cache_resize(struct flow_table *table, u32 size)
> +{
> + struct mask_cache *mc = rcu_dereference(table->mask_cache);
> + struct mask_cache *new;
> +
> + if (size == mc->cache_size)
> + return;
> +
> + new = tbl_mask_cache_alloc(size);
> + if (!new)
> + return;
> +
> + rcu_assign_pointer(table->mask_cache, new);
> + call_rcu(&mc->rcu, mask_cache_rcu_cb);
> +}
> +
> int ovs_flow_tbl_init(struct flow_table *table)
> {
> struct table_instance *ti, *ufid_ti;
> + struct mask_cache *mc;
> struct mask_array *ma;
>
> - table->mask_cache = __alloc_percpu(sizeof(struct mask_cache_entry) *
> - MC_HASH_ENTRIES,
> - __alignof__(struct mask_cache_entry));
> - if (!table->mask_cache)
> + mc = tbl_mask_cache_alloc(MC_DEFAULT_HASH_ENTRIES);
> + if (!mc)
> return -ENOMEM;
>
> ma = tbl_mask_array_alloc(MASK_ARRAY_SIZE_MIN);
> @@ -367,6 +427,7 @@ int ovs_flow_tbl_init(struct flow_table *table)
> rcu_assign_pointer(table->ti, ti);
> rcu_assign_pointer(table->ufid_ti, ufid_ti);
> rcu_assign_pointer(table->mask_array, ma);
> + rcu_assign_pointer(table->mask_cache, mc);
> table->last_rehash = jiffies;
> table->count = 0;
> table->ufid_count = 0;
> @@ -377,7 +438,7 @@ int ovs_flow_tbl_init(struct flow_table *table)
> free_mask_array:
> __mask_array_destroy(ma);
> free_mask_cache:
> - free_percpu(table->mask_cache);
> + __mask_cache_destroy(mc);
> return -ENOMEM;
> }
>
> @@ -453,9 +514,11 @@ void ovs_flow_tbl_destroy(struct flow_table *table)
> {
> struct table_instance *ti = rcu_dereference_raw(table->ti);
> struct table_instance *ufid_ti = rcu_dereference_raw(table->ufid_ti);
> + struct mask_cache *mc = rcu_dereference(table->mask_cache);
> + struct mask_array *ma = rcu_dereference_ovsl(table->mask_array);
>
> - free_percpu(table->mask_cache);
> - call_rcu(&table->mask_array->rcu, mask_array_rcu_cb);
> + call_rcu(&mc->rcu, mask_cache_rcu_cb);
> + call_rcu(&ma->rcu, mask_array_rcu_cb);
> table_instance_destroy(table, ti, ufid_ti, false);
> }
>
> @@ -724,6 +787,7 @@ struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table *tbl,
> u32 *n_mask_hit,
> u32 *n_cache_hit)
> {
> + struct mask_cache *mc = rcu_dereference(tbl->mask_cache);
> struct mask_array *ma = rcu_dereference(tbl->mask_array);
> struct table_instance *ti = rcu_dereference(tbl->ti);
> struct mask_cache_entry *entries, *ce;
> @@ -733,7 +797,7 @@ struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table *tbl,
>
> *n_mask_hit = 0;
> *n_cache_hit = 0;
> - if (unlikely(!skb_hash)) {
> + if (unlikely(!skb_hash || mc->cache_size == 0)) {
> u32 mask_index = 0;
> u32 cache = 0;
>
> @@ -749,11 +813,11 @@ struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table *tbl,
>
> ce = NULL;
> hash = skb_hash;
> - entries = this_cpu_ptr(tbl->mask_cache);
> + entries = this_cpu_ptr(mc->mask_cache);
>
> /* Find the cache entry 'ce' to operate on. */
> for (seg = 0; seg < MC_HASH_SEGS; seg++) {
> - int index = hash & (MC_HASH_ENTRIES - 1);
> + int index = hash & (mc->cache_size - 1);
> struct mask_cache_entry *e;
>
> e = &entries[index];
> @@ -867,6 +931,13 @@ int ovs_flow_tbl_num_masks(const struct flow_table *table)
> return READ_ONCE(ma->count);
> }
>
> +u32 ovs_flow_tbl_masks_cache_size(const struct flow_table *table)
> +{
> + struct mask_cache *mc = rcu_dereference(table->mask_cache);
> +
> + return READ_ONCE(mc->cache_size);
> +}
> +
> static struct table_instance *table_instance_expand(struct table_instance *ti,
> bool ufid)
> {
> @@ -1095,8 +1166,8 @@ void ovs_flow_masks_rebalance(struct flow_table *table)
> for (i = 0; i < masks_entries; i++) {
> int index = masks_and_count[i].index;
>
> - new->masks[new->count++] =
> - rcu_dereference_ovsl(ma->masks[index]);
> + if (ovsl_dereference(ma->masks[index]))
> + new->masks[new->count++] = ma->masks[index];
> }
>
> rcu_assign_pointer(table->mask_array, new);
> diff --git a/net/openvswitch/flow_table.h b/net/openvswitch/flow_table.h
> index 325e939371d8..f2dba952db2f 100644
> --- a/net/openvswitch/flow_table.h
> +++ b/net/openvswitch/flow_table.h
> @@ -27,6 +27,12 @@ struct mask_cache_entry {
> u32 mask_index;
> };
>
> +struct mask_cache {
> + struct rcu_head rcu;
> + u32 cache_size; /* Must be ^2 value. */
> + struct mask_cache_entry __percpu *mask_cache;
> +};
> +
> struct mask_count {
> int index;
> u64 counter;
> @@ -53,7 +59,7 @@ struct table_instance {
> struct flow_table {
> struct table_instance __rcu *ti;
> struct table_instance __rcu *ufid_ti;
> - struct mask_cache_entry __percpu *mask_cache;
> + struct mask_cache __rcu *mask_cache;
> struct mask_array __rcu *mask_array;
> unsigned long last_rehash;
> unsigned int count;
> @@ -77,6 +83,8 @@ int ovs_flow_tbl_insert(struct flow_table *table, struct sw_flow *flow,
> const struct sw_flow_mask *mask);
> void ovs_flow_tbl_remove(struct flow_table *table, struct sw_flow *flow);
> int ovs_flow_tbl_num_masks(const struct flow_table *table);
> +u32 ovs_flow_tbl_masks_cache_size(const struct flow_table *table);
> +void ovs_flow_tbl_masks_cache_resize(struct flow_table *table, u32 size);
> struct sw_flow *ovs_flow_tbl_dump_next(struct table_instance *table,
> u32 *bucket, u32 *idx);
> struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table *,
>
--
Best regards, Tonghao
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