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Date: Thu, 20 Apr 2017 16:24:53 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Jamal Hadi Salim <jhs@...atatu.com>
Cc: davem@...emloft.net, xiyou.wangcong@...il.com,
eric.dumazet@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v5 1/2] net sched actions: dump more than
TCA_ACT_MAX_PRIO actions per batch
Thu, Apr 20, 2017 at 04:18:50PM CEST, jhs@...atatu.com wrote:
>On 17-04-20 09:59 AM, Jiri Pirko wrote:
>> Thu, Apr 20, 2017 at 03:06:21PM CEST, jhs@...atatu.com wrote:
>> > From: Jamal Hadi Salim <jhs@...atatu.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
>> > doesn't set this flag doesn't 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 doesn't 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@...atatu.com>
>> > ---
>> > include/uapi/linux/rtnetlink.h | 21 +++++++++++++++++--
>> > net/sched/act_api.c | 46 +++++++++++++++++++++++++++++++++---------
>> > 2 files changed, 55 insertions(+), 12 deletions(-)
>> >
>> > diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
>> > index cce0613..d7d28ec 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 stands for "traffic control action action". I don't get it :(
>> Prefix still sounds wrong to me, sorry :/
>> Should be:
>> TCA_SOMETHING_*
>>
>>
>> > + TCAA_ACT_TAB,
>> > +#define TCA_ACT_TAB 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
>> > +/* 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 BIT(0)
>>
>> Please put some prefix to the name, as I asked for in the previous
>> version.
>>
>
>Didnt mean to leave out but:
>I cant seem to find it. Do you recall what you said it should be?
TCA_SOMETHING_FLAGS_LARGE_DUMP_ON
>
>>
>> >
>> > /* 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..f85b8fd 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,
>>
>> Please do this in a separate patch. It is an unrelated bug fix.
>>
>
>Ok, that is fair. Thanks. Ok, if this was patch 1/3 in next update.
Good.
>
>>
>>
>
>>
>> "tcaa" again, now as a variable :/
>> Just use "tb" as the rest of the code does.
>>
>
>Sure.
>
>>
>> >
>> > + if (tcaa[TCAA_ACT_FLAGS])
>> > + act_flags = nla_get_u32(tcaa[TCAA_ACT_FLAGS]);
>>
>> I still believe this is wrong. Should be a separate attr per flag.
>> For user experience breakage reasons:
>> 2 kernels should not behave differently on the exact same value passed
>> from userspace:
>> User passes 0x2. Now the kernel will ignore the set bit, the next kernel
>> will recognize it as a valid flag and do something.
>> Please let the discussion reach a consensus before pushing this again.
>>
>>
>
>Jiri - I dont agree. There is no such breakage. Refer to my previous
>email. Lets just move on.
Anyone else has opinion on this?
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