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

Jiri Pirko
2017-04-19T14:14:22Z

Wed, Apr 19, 2017 at 03:11:26PM CEST, jhs@mojatatu.com wrote:
>On 17-04-19 08:53 AM, Jiri Pirko wrote:
>> 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.
>>
>
>User space sets the TCAA_ACT_TIME_FILTER value.
>Jiri - this is described in the commit log ;->
>I have some tc changes which set this value.
>In the example below it was 120 seconds.

So it is hard coded. That confused me. I believe it would be good to
provide actual tc patch that does the proper changes and include the
example of that usage in the description - instead of "hackedtc"

>
>
>>
>> >
>> > 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.
>>
>
>It is a time filter. What do you want to call it?

TIME_DELTA?

>
>
>>
>> > __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
>>
>
>Sure.
>
>
>>
>> > 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?
>
>You are right - will remove this.
>
>> Just use cb->args[0] instead of 4
>>
>
>I can do that too.
>
>
>>
>> > @@ -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.
>>
>
>np.
>
>> >
>> > 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.
>>
>
>Will remove.
>
>>
>> > 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.
>>
>
>Will do - next cycle run.

Thanks.

>
>
>cheers,
>jamal