From: Jamal Hadi Salim <j...@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.
We reuse the pad fields in tcamsg. pad1 is used as a flag space.
User explicitly requests for the large dump in order to maintain
backwards compatibility with user space by setting bit
ACT_LARGE_DUMP_ON; older user space which doesnt set this flag
doesnt get the large (than 32) batches - so continues to work
as before. Older kernels ignore this flag, so legacy behavior
is maintained.
The kernel uses pad2 to tell the user how many actions are put in
a single batch. As such user space app(like tc) knows how long
to iterate 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 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
Improvement: Dump time from about 20 minutes to about 2 minutes.
Signed-off-by: Jamal Hadi Salim <j...@mojatatu.com>
---
include/uapi/linux/rtnetlink.h | 7 +++++++
net/sched/act_api.c | 17 ++++++++++++++---
2 files changed, 21 insertions(+), 3 deletions(-)
diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index cce0613..3434d98 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -678,6 +678,13 @@ 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
+/* tcamsg flags stored in tca__pad
+ *
+ * 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 tca__pad2 for user app's info
+ */
+#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 79d875c..90cc774 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:
@@ -1081,6 +1086,7 @@ static int tc_dump_action(struct sk_buff *skb, struct
netlink_callback *cb)
struct tc_action_ops *a_o;
int ret = 0;
struct tcamsg *t = (struct tcamsg *) nlmsg_data(cb->nlh);
+ unsigned char act_flags = t->tca__pad1;
struct nlattr *kind = find_dump_kind(cb->nlh);
if (kind == NULL) {
@@ -1096,9 +1102,12 @@ static int tc_dump_action(struct sk_buff *skb, struct
netlink_callback *cb)
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;
+ t->tca__pad1 = act_flags;
t->tca__pad2 = 0;
nest = nla_nest_start(skb, TCA_ACT_TAB);
@@ -1112,6 +1121,8 @@ static int tc_dump_action(struct sk_buff *skb, struct
netlink_callback *cb)
if (ret > 0) {
nla_nest_end(skb, nest);
ret = skb->len;
+ t->tca__pad2 = cb->args[1];
+ cb->args[1] = 0;
} else
nlmsg_trim(skb, b);
--
1.9.1
