[PATCH net-next v4 1/2] net sched actions: dump more than TCA_ACT_MAX_PRIO actions per batch

Jamal Hadi Salim
2017-04-19T11:57:43Z

From: Jamal Hadi Salim <jhs@mojatatu.com>

When you dump hundreds of thousands of actions, getting only 32 per
dump batch even when the socket buffer and memory allocations allow
is inefficient.

With this change, the user will get as many as possibly fitting
within the given constraints available to the kernel.

A new top level TLV space is introduced. An attribute
TCAA_ACT_FLAGS is used to carry the flags indicating the user
is capable of processing these large dumps. Older user space which
doesnt set this flag doesnt get the large (than 32) batches.
The kernel uses the TCAA_ACT_COUNT attribute to tell the user how many
actions are put in a single batch. As such user space app knows how long
to iterate (independent of the type of action being dumped)
instead of hardcoded maximum of 32.

Some results dumping 1.5M actions, first unpatched tc which the
kernel doesnt help:

prompt$ time -p tc actions ls action gact | grep index | wc -l
1500000
real 1388.43
user 2.07
sys 1386.79

Now lets see a patched tc which sets the correct flags when requesting
a dump:

prompt$ time -p updatedtc actions ls action gact | grep index | wc -l
1500000
real 178.13
user 2.02
sys 176.96

Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
---
include/uapi/linux/rtnetlink.h | 21 +++++++++++++++++++--
net/sched/act_api.c | 43 ++++++++++++++++++++++++++++++++----------
3 files changed, 53 insertions(+), 12 deletions(-)

diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index cce0613..c7080ec 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -674,10 +674,27 @@ struct tcamsg {
unsigned char tca__pad1;
unsigned short tca__pad2;
};
+
+enum {
+ TCAA_UNSPEC,
+ TCAA_ACT_TAB,
+ TCAA_ACT_FLAGS,
+ TCAA_ACT_COUNT,
+ __TCAA_MAX
+};
+
+#define TCAA_MAX (__TCAA_MAX - 1)
#define TA_RTA(r) ((struct rtattr*)(((char*)(r)) + NLMSG_ALIGN(sizeof(struct tcamsg))))
#define TA_PAYLOAD(n) NLMSG_PAYLOAD(n,sizeof(struct tcamsg))
-#define TCA_ACT_TAB 1 /* attr type must be >=1 */
-#define TCAA_MAX 1
+#define TCA_ACT_TAB TCAA_ACT_TAB
+/* tcamsg flags stored in attribute TCAA_ACT_FLAGS
+ *
+ * ACT_LARGE_DUMP_ON user->kernel to request for larger than TCA_ACT_MAX_PRIO
+ * actions in a dump. All dump responses will contain the number of actions
+ * being dumped stored in for user app's consumption in TCAA_ACT_COUNT
+ *
+ */
+#define ACT_LARGE_DUMP_ON (1 << 0)

/* New extended info filters for IFLA_EXT_MASK */
#define RTEXT_FILTER_VF (1 << 0)
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 82b1d48..45e1cf7 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -83,6 +83,7 @@ static int tcf_dump_walker(struct tcf_hashinfo *hinfo, struct sk_buff *skb,
struct netlink_callback *cb)
{
int err = 0, index = -1, i = 0, s_i = 0, n_i = 0;
+ unsigned short act_flags = cb->args[2];
struct nlattr *nest;

spin_lock_bh(&hinfo->lock);
@@ -111,14 +112,18 @@ static int tcf_dump_walker(struct tcf_hashinfo *hinfo, struct sk_buff *skb,
}
nla_nest_end(skb, nest);
n_i++;
- if (n_i >= TCA_ACT_MAX_PRIO)
+ if (!(act_flags & ACT_LARGE_DUMP_ON) &&
+ n_i >= TCA_ACT_MAX_PRIO)
goto done;
}
}
done:
spin_unlock_bh(&hinfo->lock);
- if (n_i)
+ if (n_i) {
cb->args[0] += n_i;
+ if (act_flags & ACT_LARGE_DUMP_ON)
+ cb->args[1] = n_i;
+ }
return n_i;

nla_put_failure:
@@ -993,11 +998,15 @@ static int tcf_action_add(struct net *net, struct nlattr *nla,
return tcf_add_notify(net, n, &actions, portid);
}

+static const struct nla_policy tcaa_policy[TCAA_MAX + 1] = {
+ [TCAA_ACT_FLAGS] = { .type = NLA_U32 },
+};
+
static int tc_ctl_action(struct sk_buff *skb, struct nlmsghdr *n,
struct netlink_ext_ack *extack)
{
struct net *net = sock_net(skb->sk);
- struct nlattr *tca[TCA_ACT_MAX + 1];
+ struct nlattr *tca[TCAA_MAX + 1];
u32 portid = skb ? NETLINK_CB(skb).portid : 0;
int ret = 0, ovr = 0;

@@ -1005,7 +1014,7 @@ static int tc_ctl_action(struct sk_buff *skb, struct nlmsghdr *n,
!netlink_capable(skb, CAP_NET_ADMIN))
return -EPERM;

- ret = nlmsg_parse(n, sizeof(struct tcamsg), tca, TCA_ACT_MAX, NULL,
+ ret = nlmsg_parse(n, sizeof(struct tcamsg), tca, TCAA_MAX, tcaa_policy,
extack);
if (ret < 0)
return ret;
@@ -1046,16 +1055,12 @@ static int tc_ctl_action(struct sk_buff *skb, struct nlmsghdr *n,
return ret;
}

-static struct nlattr *find_dump_kind(const struct nlmsghdr *n)
+static struct nlattr *find_dump_kind(struct nlattr **nla)
{
struct nlattr *tb1, *tb2[TCA_ACT_MAX + 1];
struct nlattr *tb[TCA_ACT_MAX_PRIO + 1];
- struct nlattr *nla[TCAA_MAX + 1];
struct nlattr *kind;

- if (nlmsg_parse(n, sizeof(struct tcamsg), nla, TCAA_MAX,
- NULL, NULL) < 0)
- return NULL;
tb1 = nla[TCA_ACT_TAB];
if (tb1 == NULL)
return NULL;
@@ -1081,9 +1086,18 @@ static int tc_dump_action(struct sk_buff *skb, struct netlink_callback *cb)
struct nlattr *nest;
struct tc_action_ops *a_o;
int ret = 0;
+ struct nlattr *tcaa[TCAA_MAX + 1];
struct tcamsg *t = (struct tcamsg *) nlmsg_data(cb->nlh);
- struct nlattr *kind = find_dump_kind(cb->nlh);
+ struct nlattr *kind = NULL;
+ u32 act_flags = 0;
+
+ ret = nlmsg_parse(cb->nlh, sizeof(struct tcamsg), tcaa, TCAA_MAX,
+ tcaa_policy, NULL);
+ if (ret < 0)
+ return ret;
+

+ kind = find_dump_kind(tcaa);
if (kind == NULL) {
pr_info("tc_dump_action: action bad kind\n");
return 0;
@@ -1093,10 +1107,16 @@ static int tc_dump_action(struct sk_buff *skb, struct netlink_callback *cb)
if (a_o == NULL)
return 0;

+ if (tcaa[TCAA_ACT_FLAGS])
+ act_flags = nla_get_u32(tcaa[TCAA_ACT_FLAGS]);
+
nlh = nlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
cb->nlh->nlmsg_type, sizeof(*t), 0);
if (!nlh)
goto out_module_put;
+
+ cb->args[2] = act_flags;
+
t = nlmsg_data(nlh);
t->tca_family = AF_UNSPEC;
t->tca__pad1 = 0;
@@ -1113,6 +1133,9 @@ static int tc_dump_action(struct sk_buff *skb, struct netlink_callback *cb)
if (ret > 0) {
nla_nest_end(skb, nest);
ret = skb->len;
+ if (nla_put_u32(skb, TCAA_ACT_COUNT, cb->args[1]))
+ goto out_module_put;
+ cb->args[1] = 0;
} else
nlmsg_trim(skb, b);

--
1.9.1