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Message-ID: <CAMDZJNXh_1BFRnypUNLgmF5E4s-qN1cg=0Jqr5RoR5bSNgV-FQ@mail.gmail.com>
Date: Mon, 20 Apr 2020 08:23:17 +0800
From: Tonghao Zhang <xiangxia.m.yue@...il.com>
To: Pravin Shelar <pravin.ovn@...il.com>
Cc: Andy Zhou <azhou@....org>, Ben Pfaff <blp@....org>,
William Tu <u9012063@...il.com>,
Linux Kernel Network Developers <netdev@...r.kernel.org>,
ovs dev <dev@...nvswitch.org>
Subject: Re: [PATCH net-next v2 1/5] net: openvswitch: expand the meters
supported number
On Mon, Apr 20, 2020 at 1:29 AM Pravin Shelar <pravin.ovn@...il.com> wrote:
>
> On Sat, Apr 18, 2020 at 10:25 AM <xiangxia.m.yue@...il.com> wrote:
> >
> > From: Tonghao Zhang <xiangxia.m.yue@...il.com>
> >
> > In kernel datapath of Open vSwitch, there are only 1024
> > buckets of meter in one dp. If installing more than 1024
> > (e.g. 8192) meters, it may lead to the performance drop.
> > But in some case, for example, Open vSwitch used as edge
> > gateway, there should be 200,000+ at least, meters used for
> > IP address bandwidth limitation.
> >
> > [Open vSwitch userspace datapath has this issue too.]
> >
> > For more scalable meter, this patch expands the buckets
> > when necessary, so we can install more meters in the datapath.
> > Introducing the struct *dp_meter_instance*, it's easy to
> > expand meter though changing the *ti* point in the struct
> > *dp_meter_table*.
> >
> > Cc: Pravin B Shelar <pshelar@....org>
> > Cc: Andy Zhou <azhou@....org>
> > Signed-off-by: Tonghao Zhang <xiangxia.m.yue@...il.com>
> > ---
> > net/openvswitch/datapath.h | 2 +-
> > net/openvswitch/meter.c | 200 +++++++++++++++++++++++++++++--------
> > net/openvswitch/meter.h | 15 ++-
> > 3 files changed, 169 insertions(+), 48 deletions(-)
> >
> > diff --git a/net/openvswitch/datapath.h b/net/openvswitch/datapath.h
> > index e239a46c2f94..785105578448 100644
> > --- a/net/openvswitch/datapath.h
> > +++ b/net/openvswitch/datapath.h
> > @@ -82,7 +82,7 @@ struct datapath {
> > u32 max_headroom;
> >
> > /* Switch meters. */
> > - struct hlist_head *meters;
> > + struct dp_meter_table *meters;
> lets define it as part of this struct to avoid indirection.
>
> > };
> >
> > /**
> > diff --git a/net/openvswitch/meter.c b/net/openvswitch/meter.c
> > index 5010d1ddd4bd..494a0014ecd8 100644
> > --- a/net/openvswitch/meter.c
> > +++ b/net/openvswitch/meter.c
> > @@ -19,8 +19,6 @@
> > #include "datapath.h"
> > #include "meter.h"
> >
> > -#define METER_HASH_BUCKETS 1024
> > -
> > static const struct nla_policy meter_policy[OVS_METER_ATTR_MAX + 1] = {
> > [OVS_METER_ATTR_ID] = { .type = NLA_U32, },
> > [OVS_METER_ATTR_KBPS] = { .type = NLA_FLAG },
> > @@ -39,6 +37,11 @@ static const struct nla_policy band_policy[OVS_BAND_ATTR_MAX + 1] = {
> > [OVS_BAND_ATTR_STATS] = { .len = sizeof(struct ovs_flow_stats) },
> > };
> >
> > +static u32 meter_hash(struct dp_meter_instance *ti, u32 id)
> > +{
> > + return id % ti->n_meters;
> > +}
> > +
> > static void ovs_meter_free(struct dp_meter *meter)
> > {
> > if (!meter)
> > @@ -47,40 +50,141 @@ static void ovs_meter_free(struct dp_meter *meter)
> > kfree_rcu(meter, rcu);
> > }
> >
> > -static struct hlist_head *meter_hash_bucket(const struct datapath *dp,
> > - u32 meter_id)
> > -{
> > - return &dp->meters[meter_id & (METER_HASH_BUCKETS - 1)];
> > -}
> > -
> > /* Call with ovs_mutex or RCU read lock. */
> > -static struct dp_meter *lookup_meter(const struct datapath *dp,
> > +static struct dp_meter *lookup_meter(const struct dp_meter_table *tbl,
> > u32 meter_id)
> > {
> > + struct dp_meter_instance *ti = rcu_dereference_ovsl(tbl->ti);
> > + u32 hash = meter_hash(ti, meter_id);
> > struct dp_meter *meter;
> > - struct hlist_head *head;
> >
> > - head = meter_hash_bucket(dp, meter_id);
> > - hlist_for_each_entry_rcu(meter, head, dp_hash_node,
> > - lockdep_ovsl_is_held()) {
> > - if (meter->id == meter_id)
> > - return meter;
> > - }
> > + meter = rcu_dereference_ovsl(ti->dp_meters[hash]);
> > + if (meter && likely(meter->id == meter_id))
> > + return meter;
> > +
> > return NULL;
> > }
> >
> > -static void attach_meter(struct datapath *dp, struct dp_meter *meter)
> > +static struct dp_meter_instance *dp_meter_instance_alloc(const u32 size)
> > +{
> > + struct dp_meter_instance *ti;
> > +
> > + ti = kvzalloc(sizeof(*ti) +
> > + sizeof(struct dp_meter *) * size,
> > + GFP_KERNEL);
> > + if (!ti)
> > + return NULL;
> Given this is a kernel space array we need to have hard limit inplace.
In patch 2, I limited the meter number, should we add hard limit here ?
> > +
> > + ti->n_meters = size;
> > +
> > + return ti;
> > +}
> > +
> > +static void dp_meter_instance_free(struct dp_meter_instance *ti)
> > +{
> > + kvfree(ti);
> > +}
> > +
> > +static void dp_meter_instance_free_rcu(struct rcu_head *rcu)
> > +{
> > + struct dp_meter_instance *ti;
> > +
> > + ti = container_of(rcu, struct dp_meter_instance, rcu);
> > + kvfree(ti);
> > +}
> > +
> > +static int
> > +dp_meter_instance_realloc(struct dp_meter_table *tbl, u32 size)
> > +{
> > + struct dp_meter_instance *ti = rcu_dereference_ovsl(tbl->ti);
> > + int n_meters = min(size, ti->n_meters);
> > + struct dp_meter_instance *new_ti;
> > + int i;
> > +
> > + new_ti = dp_meter_instance_alloc(size);
> > + if (!new_ti)
> > + return -ENOMEM;
> > +
> > + for (i = 0; i < n_meters; i++)
> > + new_ti->dp_meters[i] =
> > + rcu_dereference_ovsl(ti->dp_meters[i]);
> > +
> > + rcu_assign_pointer(tbl->ti, new_ti);
> > + call_rcu(&ti->rcu, dp_meter_instance_free_rcu);
> > +
> > + return 0;
> > +}
> > +
> > +static void dp_meter_instance_insert(struct dp_meter_instance *ti,
> > + struct dp_meter *meter)
> > +{
> > + u32 hash;
> > +
> > + hash = meter_hash(ti, meter->id);
> > + rcu_assign_pointer(ti->dp_meters[hash], meter);
> > +}
> > +
> > +static void dp_meter_instance_remove(struct dp_meter_instance *ti,
> > + struct dp_meter *meter)
> > {
> > - struct hlist_head *head = meter_hash_bucket(dp, meter->id);
> > + u32 hash;
> >
> > - hlist_add_head_rcu(&meter->dp_hash_node, head);
> > + hash = meter_hash(ti, meter->id);
> > + RCU_INIT_POINTER(ti->dp_meters[hash], NULL);
> > }
> >
> > -static void detach_meter(struct dp_meter *meter)
> > +static int attach_meter(struct dp_meter_table *tbl, struct dp_meter *meter)
> > {
> > + struct dp_meter_instance *ti = rcu_dereference_ovsl(tbl->ti);
> > + u32 hash = meter_hash(ti, meter->id);
> > +
> > + /*
> > + * In generally, slot selected should be empty, because
> > + * OvS uses id-pool to fetch a available id.
> > + */
> > + if (unlikely(rcu_dereference_ovsl(ti->dp_meters[hash])))
> > + return -EINVAL;
> we could return -EBUSY instead.
> > +
> > + dp_meter_instance_insert(ti, meter);
> > +
> > + /* That function is thread-safe. */
> > + if (++tbl->count >= ti->n_meters)
> > + if (dp_meter_instance_realloc(tbl, ti->n_meters * 2))
> > + goto expand_err;
> > +
> > + return 0;
> > +
> > +expand_err:
> > + dp_meter_instance_remove(ti, meter);
> > + tbl->count--;
> > + return -ENOMEM;
> > +}
> > +
> > +static void detach_meter(struct dp_meter_table *tbl, struct dp_meter *meter)
> > +{
> > + struct dp_meter_instance *ti;
> > +
> > ASSERT_OVSL();
> > - if (meter)
> > - hlist_del_rcu(&meter->dp_hash_node);
> > + if (!meter)
> > + return;
> > +
> > + ti = rcu_dereference_ovsl(tbl->ti);
> > + dp_meter_instance_remove(ti, meter);
> > +
> > + tbl->count--;
> > +
> > + /* Shrink the meter array if necessary. */
> > + if (ti->n_meters > DP_METER_ARRAY_SIZE_MIN &&
> > + tbl->count <= (ti->n_meters / 4)) {
> > + int half_size = ti->n_meters / 2;
> > + int i;
> > +
> Lets add a comment about this.
> > + for (i = half_size; i < ti->n_meters; i++)
> > + if (rcu_dereference_ovsl(ti->dp_meters[i]))
> > + return;
> > +
> > + dp_meter_instance_realloc(tbl, half_size);
> > + }
> > }
> >
> > static struct sk_buff *
> > @@ -303,9 +407,13 @@ static int ovs_meter_cmd_set(struct sk_buff *skb, struct genl_info *info)
> > meter_id = nla_get_u32(a[OVS_METER_ATTR_ID]);
> >
> > /* Cannot fail after this. */
> > - old_meter = lookup_meter(dp, meter_id);
> > - detach_meter(old_meter);
> > - attach_meter(dp, meter);
> > + old_meter = lookup_meter(dp->meters, meter_id);
> in new scheme this can fail due to hash collision, lets check for NULL.
If old_meter is NULL, detach_meter will do nothing.
> > + detach_meter(dp->meters, old_meter);
> > +
> > + err = attach_meter(dp->meters, meter);
> > + if (err)
> > + goto exit_unlock;
> > +
> > ovs_unlock();
> >
> > /* Build response with the meter_id and stats from
> > @@ -365,7 +473,7 @@ static int ovs_meter_cmd_get(struct sk_buff *skb, struct genl_info *info)
> > }
> >
> > /* Locate meter, copy stats. */
> > - meter = lookup_meter(dp, meter_id);
> > + meter = lookup_meter(dp->meters, meter_id);
> > if (!meter) {
> > err = -ENOENT;
> > goto exit_unlock;
> > @@ -416,13 +524,13 @@ static int ovs_meter_cmd_del(struct sk_buff *skb, struct genl_info *info)
> > goto exit_unlock;
> > }
> >
> > - old_meter = lookup_meter(dp, meter_id);
> > + old_meter = lookup_meter(dp->meters, meter_id);
> > if (old_meter) {
> > spin_lock_bh(&old_meter->lock);
> > err = ovs_meter_cmd_reply_stats(reply, meter_id, old_meter);
> > WARN_ON(err);
> > spin_unlock_bh(&old_meter->lock);
> > - detach_meter(old_meter);
> > + detach_meter(dp->meters, old_meter);
> > }
> > ovs_unlock();
> > ovs_meter_free(old_meter);
> > @@ -452,7 +560,7 @@ bool ovs_meter_execute(struct datapath *dp, struct sk_buff *skb,
> > int i, band_exceeded_max = -1;
> > u32 band_exceeded_rate = 0;
> >
> > - meter = lookup_meter(dp, meter_id);
> > + meter = lookup_meter(dp->meters, meter_id);
> > /* Do not drop the packet when there is no meter. */
> > if (!meter)
> > return false;
> > @@ -570,32 +678,36 @@ struct genl_family dp_meter_genl_family __ro_after_init = {
> >
> > int ovs_meters_init(struct datapath *dp)
> > {
> > - int i;
> > + struct dp_meter_instance *ti;
> > + struct dp_meter_table *tbl;
> > +
> > + tbl = kmalloc(sizeof(*tbl), GFP_KERNEL);
> > + if (!tbl)
> > + return -ENOMEM;
> >
> > - dp->meters = kmalloc_array(METER_HASH_BUCKETS,
> > - sizeof(struct hlist_head), GFP_KERNEL);
> > + tbl->count = 0;
> >
> > - if (!dp->meters)
> > + ti = dp_meter_instance_alloc(DP_METER_ARRAY_SIZE_MIN);
> > + if (!ti) {
> > + kfree(tbl);
> > return -ENOMEM;
> > + }
> >
> > - for (i = 0; i < METER_HASH_BUCKETS; i++)
> > - INIT_HLIST_HEAD(&dp->meters[i]);
> > + rcu_assign_pointer(tbl->ti, ti);
> > + dp->meters = tbl;
> >
> > return 0;
> > }
> >
> > void ovs_meters_exit(struct datapath *dp)
> > {
> > + struct dp_meter_table *tbl = dp->meters;
> > + struct dp_meter_instance *ti = rcu_dereference_ovsl(tbl->ti);
> > int i;
> >
> > - for (i = 0; i < METER_HASH_BUCKETS; i++) {
> > - struct hlist_head *head = &dp->meters[i];
> > - struct dp_meter *meter;
> > - struct hlist_node *n;
> > -
> > - hlist_for_each_entry_safe(meter, n, head, dp_hash_node)
> > - kfree(meter);
> > - }
> > + for (i = 0; i < ti->n_meters; i++)
> > + ovs_meter_free(ti->dp_meters[i]);
> >
> > - kfree(dp->meters);
> > + dp_meter_instance_free(ti);
> > + kfree(tbl);
> > }
> > diff --git a/net/openvswitch/meter.h b/net/openvswitch/meter.h
> > index f645913870bd..d91940383bbe 100644
> > --- a/net/openvswitch/meter.h
> > +++ b/net/openvswitch/meter.h
> > @@ -18,6 +18,7 @@
> > struct datapath;
> >
> > #define DP_MAX_BANDS 1
> > +#define DP_METER_ARRAY_SIZE_MIN (1ULL << 10)
> >
> > struct dp_meter_band {
> > u32 type;
> > @@ -30,9 +31,6 @@ struct dp_meter_band {
> > struct dp_meter {
> > spinlock_t lock; /* Per meter lock */
> > struct rcu_head rcu;
> > - struct hlist_node dp_hash_node; /*Element in datapath->meters
> > - * hash table.
> > - */
> > u32 id;
> > u16 kbps:1, keep_stats:1;
> > u16 n_bands;
> > @@ -42,6 +40,17 @@ struct dp_meter {
> > struct dp_meter_band bands[];
> > };
> >
> > +struct dp_meter_instance {
> > + struct rcu_head rcu;
> > + u32 n_meters;
> > + struct dp_meter __rcu *dp_meters[];
> > +};
> > +
> > +struct dp_meter_table {
> > + struct dp_meter_instance __rcu *ti;
> > + u32 count;
> > +};
> > +
> > extern struct genl_family dp_meter_genl_family;
> > int ovs_meters_init(struct datapath *dp);
> > void ovs_meters_exit(struct datapath *dp);
> > --
> > 2.23.0
> >
--
Best regards, Tonghao
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