Re: [PATCH net-next v4 2/2] net sched actions: add time filter for action dumping

Jiri Pirko
2017-04-19T12:53:49Z

Wed, Apr 19, 2017 at 01:57:30PM CEST, jhs@mojatatu.com wrote:
>From: Jamal Hadi Salim <jhs@mojatatu.com>
>
>This adds support for filtering based on time since last used.
>When we are dumping a large number of actions it is useful to
>have the option of filtering based on when the action was last
>used to reduce the amount of data crossing to user space.
>
>With this patch the user space app sets the TCAA_ACT_TIME_FILTER
>attribute with the value in milliseconds with "time of interest
>since now". The kernel converts this to jiffies and does the
>filtering comparison matching entries that have seen activity
>since then and returns them to user space.
>Old kernels and old tc continue to work in legacy mode since
>they dont specify this attribute.
>
>Some example (we have 400 actions bound to 400 filters); at installation
>time using hacked tc which sets the time of interest to 120 seconds:
>
>prompt$ hackedtc actions ls action gact | grep index | wc -l
>400
>
>go get some coffee and wait for > 120 seconds and try again:
>
>prompt$ hackedtc actions ls action gact | grep index | wc -l
>0
>
>Lets see a filter bound to one of these actions:
>..
>filter pref 10 u32
>filter pref 10 u32 fh 800: ht divisor 1
>filter pref 10 u32 fh 800::800 order 2048 key ht 800 bkt 0 flowid 1:10 (rule hit 2 success 1)
> match 7f000002/ffffffff at 12 (success 1 )
> action order 1: gact action pass
> random type none pass val 0
> index 23 ref 2 bind 1 installed 1145 sec used 802 sec
> Action statistics:
> Sent 84 bytes 1 pkt (dropped 0, overlimits 0 requeues 0)
> backlog 0b 0p requeues 0
>....
>
>that coffee took long, no? It was good.
>
>Now lets ping -c 1 127.0.0.2, then run the actions again:
>
>prompt$ hackedtc actions ls action gact | grep index | wc -l
>1
>
>More details please:
>
>prompt$ hackedtc -s actions ls action gact

I don't see where you pass the time.

>
> action order 0: gact action pass
> random type none pass val 0
> index 23 ref 2 bind 1 installed 1270 sec used 30 sec
> Action statistics:
> Sent 168 bytes 2 pkt (dropped 0, overlimits 0 requeues 0)
> backlog 0b 0p requeues 0
>
>And the filter?
>
>filter pref 10 u32
>filter pref 10 u32 fh 800: ht divisor 1
>filter pref 10 u32 fh 800::800 order 2048 key ht 800 bkt 0 flowid 1:10 (rule hit 4 success 2)
> match 7f000002/ffffffff at 12 (success 2 )
> action order 1: gact action pass
> random type none pass val 0
> index 23 ref 2 bind 1 installed 1324 sec used 84 sec
> Action statistics:
> Sent 168 bytes 2 pkt (dropped 0, overlimits 0 requeues 0)
> backlog 0b 0p requeues 0
>
>Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
>---
> include/uapi/linux/rtnetlink.h | 1 +
> net/sched/act_api.c | 25 +++++++++++++++++++++++--
> 2 files changed, 24 insertions(+), 2 deletions(-)
>
>diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
>index c7080ec..1b36cc0 100644
>--- a/include/uapi/linux/rtnetlink.h
>+++ b/include/uapi/linux/rtnetlink.h
>@@ -680,6 +680,7 @@ enum {
> TCAA_ACT_TAB,
> TCAA_ACT_FLAGS,
> TCAA_ACT_COUNT,
>+ TCAA_ACT_TIME_FILTER,

Another use of word "filter" for something else. I believe that we need
to reduce confusion, not to make it worse.

> __TCAA_MAX
> };
>
>diff --git a/net/sched/act_api.c b/net/sched/act_api.c
>index 45e1cf7..b03863a 100644
>--- a/net/sched/act_api.c
>+++ b/net/sched/act_api.c
>@@ -84,11 +84,12 @@ static int tcf_dump_walker(struct tcf_hashinfo *hinfo, struct sk_buff *skb,
> {
> int err = 0, index = -1, i = 0, s_i = 0, n_i = 0;
> unsigned short act_flags = cb->args[2];
>+ unsigned long jiffy_filter = cb->args[3];

call this "jiffy_since" for example

> struct nlattr *nest;
>
> spin_lock_bh(&hinfo->lock);
>
>- s_i = cb->args[0];
>+ s_i = cb->args[4];
>
> for (i = 0; i < (hinfo->hmask + 1); i++) {
> struct hlist_head *head;
>@@ -101,6 +102,11 @@ static int tcf_dump_walker(struct tcf_hashinfo *hinfo, struct sk_buff *skb,
> if (index < s_i)
> continue;
>
>+ if (jiffy_filter &&
>+ time_after(jiffy_filter,
>+ (unsigned long)p->tcfa_tm.lastuse))
>+ continue;
>+
> nest = nla_nest_start(skb, n_i);
> if (nest == NULL)
> goto nla_put_failure;
>@@ -118,6 +124,9 @@ static int tcf_dump_walker(struct tcf_hashinfo *hinfo, struct sk_buff *skb,
> }
> }
> done:
>+ if (index > 0)
>+ cb->args[4] = index + 1;
>+
> spin_unlock_bh(&hinfo->lock);
> if (n_i) {
> cb->args[0] += n_i;

You don't use "cb->args[0]" anymore. Why do you need this?
Just use cb->args[0] instead of 4

>@@ -1000,6 +1009,7 @@ static int tcf_action_add(struct net *net, struct nlattr *nla,
>
> static const struct nla_policy tcaa_policy[TCAA_MAX + 1] = {
> [TCAA_ACT_FLAGS] = { .type = NLA_U32 },
>+ [TCAA_ACT_TIME_FILTER] = { .type = NLA_U32 },
> };
>
> static int tc_ctl_action(struct sk_buff *skb, struct nlmsghdr *n,
>@@ -1090,13 +1100,14 @@ static int tc_dump_action(struct sk_buff *skb, struct netlink_callback *cb)
> struct tcamsg *t = (struct tcamsg *) nlmsg_data(cb->nlh);
> struct nlattr *kind = NULL;
> u32 act_flags = 0;
>+ u32 msecs_filter = 0;
>+ unsigned long jiffy_wanted = 0;

Also, "jiffy_since". Same variable, same name please.

>
> ret = nlmsg_parse(cb->nlh, sizeof(struct tcamsg), tcaa, TCAA_MAX,
> tcaa_policy, NULL);
> if (ret < 0)
> return ret;
>
>-

This should not be part of this patch.

> kind = find_dump_kind(tcaa);
> if (kind == NULL) {
> pr_info("tc_dump_action: action bad kind\n");
>@@ -1110,12 +1121,22 @@ static int tc_dump_action(struct sk_buff *skb, struct netlink_callback *cb)
> if (tcaa[TCAA_ACT_FLAGS])
> act_flags = nla_get_u32(tcaa[TCAA_ACT_FLAGS]);
>
>+ if (tcaa[TCAA_ACT_TIME_FILTER])
>+ msecs_filter = nla_get_u32(tcaa[TCAA_ACT_TIME_FILTER]);
>+
> 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;
>
>+ if (msecs_filter) {
>+ unsigned long jiffy_msecs = msecs_to_jiffies(msecs_filter);
>+
>+ jiffy_wanted = jiffies - jiffy_msecs;

you can do just:
jiffy_wanted = jiffies - msecs_to_jiffies(msecs_filter);

Also, you can put this under "if (tcaa[TCAA_ACT_TIME_FILTER])" so it's
all in one place.

>+ }
>+
> cb->args[2] = act_flags;
>+ cb->args[3] = jiffy_wanted;
>
> t = nlmsg_data(nlh);
> t->tca_family = AF_UNSPEC;
>--
>1.9.1
>