netdev - Re: [PATCH net-next v5 1/2] net sched actions: dump more than TCA_ACT_MAX

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Date:   Thu, 20 Apr 2017 10:25:11 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Jiri Pirko <jiri@...nulli.us>
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

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 :(

TC Action Attributes == TCAA.

> Prefix still sounds wrong to me, sorry :/
> Should be:
> TCA_SOMETHING_*
>

TCA_ATTR_XXX ?

I have another opportunity to make a change  where we should close
the discussion on this. We cant drag it forever.

cheers,
jamal