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Date: Thu, 30 Jul 2020 22:23:23 +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 Thu, Jul 30, 2020 at 9:52 PM Eelco Chaudron <echaudro@...hat.com> wrote:
>
>
>
> On 30 Jul 2020, at 15:25, Tonghao Zhang wrote:
>
> > On Thu, Jul 30, 2020 at 8:33 PM Eelco Chaudron <echaudro@...hat.com>
> > wrote:
> >>
> >> Thanks Tonghao for the review, see comments inline below!
> >>
> >> If I get no more reviews by the end of the week I’ll send out a v4.
> >>
> >> //Eelco
> >>
> >>
> >> On 30 Jul 2020, at 7:07, Tonghao Zhang wrote:
> >>
> >>> 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
> >>
> >> Initially, I did not do this due to the fact the new value is
> >> reported,
> >> and on failure, the old value is shown.
> >> However thinking about it again, it makes more sense to return an
> >> error.
> >> Will sent a v4 with the following to return:
> >>
> >> -
> >> -void ovs_flow_tbl_masks_cache_resize(struct flow_table *table, u32
> >> size)
> >> +int 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;
> >> + return 0;
> >> +
> >> + if (!is_power_of_2(size) && size != 0)
> >> + return -EINVAL;
> > add check as below, and we can remove the check in
> > tbl_mask_cache_alloc function. That
> > function will only return NULL, if there is no memory. And we can
> > comment for tbl_mask_cache_alloc, to indicate that size should be a
> > power of 2.
> > if ((!is_power_of_2(size) && size != 0) ||
> > (size * sizeof(struct mask_cache_entry)) >
> > PCPU_MIN_UNIT_SIZE)
>
> I do not think the extra check hurts as it’s not in any fast path.
Hi Eelco.
Yes, I agree. Sorry for not being clear. I mean that:
if we don't check the "(size * sizeof(struct mask_cache_entry)) >
PCPU_MIN_UNIT_SIZE)" in the ovs_flow_tbl_masks_cache_resize.
tbl_mask_cache_alloc (ovs_flow_tbl_masks_cache_resize will invoke this
function)will return the NULL,
ovs_flow_tbl_masks_cache_resize will return -ENOMEM. I guess we should
return -EINVAL in that case.
> The comment would easily be missed, especially if someone changes the
> default value, so I would prefer to keep it as is.
>
> > Thanks Eelco.
> > Reviewed-by: Tonghao Zhang <xiangxia.m.yue@...il.com>
> >
> >> new = tbl_mask_cache_alloc(size);
> >> if (!new)
> >> - return;
> >> + return -ENOMEM;
> >>
> >> rcu_assign_pointer(table->mask_cache, new);
> >> call_rcu(&mc->rcu, mask_cache_rcu_cb);
> >> +
> >> + return 0;
> >> }
> >>
> >>>> + }
> >>>> +
> >>>> 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".
> >>
> >> Makes sense, will remove the if() check.
> >>
> >>>> + 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
> >>
> >
> >
> > --
> > Best regards, Tonghao
>
--
Best regards, Tonghao
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