From: "Medvedkin, Vladimir" <vladimir.medvedkin@intel.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
"Ruifeng Wang (Arm Technology China)" <Ruifeng.Wang@arm.com>,
"bruce.richardson@intel.com" <bruce.richardson@intel.com>,
"dev@dpdk.org" <dev@dpdk.org>,
"Gavin Hu (Arm Technology China)" <Gavin.Hu@arm.com>,
nd <nd@arm.com>
Subject: Re: [dpdk-dev] [PATCH v3 1/3] lib/lpm: not inline unnecessary functions
Date: Fri, 5 Jul 2019 11:31:36 +0100 [thread overview]
Message-ID: <6a78a166-f19c-5444-0a1a-a74aa06463b1@intel.com> (raw)
In-Reply-To: <20190628083507.31eca1db@hermes.lan>
Hi Stephen,
On 28/06/2019 16:35, Stephen Hemminger wrote:
> On Fri, 28 Jun 2019 15:16:30 +0100
> "Medvedkin, Vladimir" <vladimir.medvedkin@intel.com> wrote:
>
>> Hi Honnappa,
>>
>> On 28/06/2019 14:57, Honnappa Nagarahalli wrote:
>>>> Hi all,
>>>>
>>>> On 28/06/2019 05:34, Stephen Hemminger wrote:
>>>>> On Fri, 28 Jun 2019 02:44:54 +0000
>>>>> "Ruifeng Wang (Arm Technology China)"<Ruifeng.Wang@arm.com> wrote:
>>>>>
>>>>>>>> Tests showed that the function inlining caused performance drop on
>>>>>>>> some x86 platforms with the memory ordering patches applied.
>>>>>>>> By force no-inline functions, the performance was better than
>>>>>>>> before on x86 and no impact to arm64 platforms.
>>>>>>>>
>>>>>>>> Suggested-by: Medvedkin Vladimir<vladimir.medvedkin@intel.com>
>>>>>>>> Signed-off-by: Ruifeng Wang<ruifeng.wang@arm.com>
>>>>>>>> Reviewed-by: Gavin Hu<gavin.hu@arm.com>
>>>>>>> {
>>>>>>>
>>>>>>> Do you actually need to force noinline or is just taking of inline enough?
>>>>>>> In general, letting compiler decide is often best practice.
>>>>>> The force noinline is an optimization for x86 platforms to keep
>>>>>> rte_lpm_add() API performance with memory ordering applied.
>>>>> I don't think you answered my question. What does a recent version of
>>>>> GCC do if you drop the inline.
>>>>>
>>>>> Actually all the functions in rte_lpm should drop inline.
>>>> I'm agree with Stephen. If it is not a fastpath and size of function is not
>>>> minimal it is good to remove inline qualifier for other control plane functions
>>>> such as rule_add/delete/find/etc and let the compiler decide to inline it
>>>> (unless it affects performance).
>>> IMO, the rule needs to be simple. If it is control plane function, we should leave it to the compiler to decide. I do not think we need to worry too much about performance for control plane functions.
>> Control plane is not as important as data plane speed but it is still
>> important. For lpm we are talking not about initialization, but runtime
>> routes add/del related functions. If it is very slow the library will be
>> totally unusable because after it receives a route update it will be
>> blocked for a long time and route update queue would overflow.
> Control plane performance is more impacted by algorithmic choice.
> The original LPM had terrible (n^2?) control path. Current code is better.
> I had a patch using RB tree, but it was rejected because it used the
> /usr/include/bsd/sys/tree.h which added a dependency.
You're absolutely right, control plane performance is mostly depends on
algorithm. Current LPM implementation has number of problems there. One
problem is rules_tbl[] that is a flat array containing routes for
control plane purposes. Replacing it with a rb-tree solves this problem,
but there are another problems. For example, when you try to add a route
10.0.0.0/8 while a number of subroutes are exist in the table (for
example 10.20.0.0/16), current implementation will load tbl_entry -> do
some checks (depth, ext entry) -> conditionally store new entry. Under
several circumstances it would take a lot time. But in fact it needs to
unconditionally rewrite only two ranges - from 10.0.0.0 to 10.19.255.255
and from 10.21.0.0 to 10.255.255.255. And control plane could help us to
get this two ranges. The best struct to do so is lc-tree because it is
relatively easy to traverse subtree (described by 10.0.0.0/8) and get
subroutes. We are working on a new implementation, hopefully it will be
ready soon.
--
Regards,
Vladimir
next prev parent reply other threads:[~2019-07-05 10:31 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-27 9:37 Ruifeng Wang
2019-06-27 9:37 ` [dpdk-dev] [PATCH v3 2/3] lib/lpm: memory orderings to avoid race conditions for v1604 Ruifeng Wang
2019-06-27 9:37 ` [dpdk-dev] [PATCH v3 3/3] lib/lpm: memory orderings to avoid race conditions for v20 Ruifeng Wang
2019-06-28 13:33 ` Medvedkin, Vladimir
2019-06-29 17:35 ` Honnappa Nagarahalli
2019-07-05 13:45 ` Alex Kiselev
2019-07-05 16:56 ` Medvedkin, Vladimir
2019-07-01 7:08 ` Ruifeng Wang (Arm Technology China)
2019-06-27 15:24 ` [dpdk-dev] [PATCH v3 1/3] lib/lpm: not inline unnecessary functions Stephen Hemminger
2019-06-28 2:44 ` Ruifeng Wang (Arm Technology China)
2019-06-28 4:34 ` Stephen Hemminger
2019-06-28 5:48 ` Ruifeng Wang (Arm Technology China)
2019-06-28 13:47 ` Medvedkin, Vladimir
2019-06-28 13:57 ` Honnappa Nagarahalli
2019-06-28 14:16 ` Medvedkin, Vladimir
2019-06-28 15:35 ` Stephen Hemminger
2019-07-01 6:44 ` Ruifeng Wang (Arm Technology China)
2019-07-05 10:40 ` Medvedkin, Vladimir
2019-07-05 10:58 ` Ruifeng Wang (Arm Technology China)
2019-07-05 10:31 ` Medvedkin, Vladimir [this message]
2019-07-05 13:37 ` Alex Kiselev
2019-07-05 16:53 ` Medvedkin, Vladimir
2019-06-28 13:38 ` Medvedkin, Vladimir
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