[dpdk-dev] [PATCH v4 1/9] examples/ipsec-secgw: avoid to request unused TX offloads

Akhil Goyal akhil.goyal at nxp.com
Mon Dec 24 11:55:43 CET 2018



On 12/24/2018 4:24 PM, Akhil Goyal wrote:
>
> On 12/24/2018 3:49 PM, Ananyev, Konstantin wrote:
>>>>> On 12/14/2018 10:10 PM, Konstantin Ananyev wrote:
>>>>>> ipsec-secgw always enables TX offloads
>>>>>> (DEV_TX_OFFLOAD_MULTI_SEGS, DEV_TX_OFFLOAD_SECURITY),
>>>>>> even when they are not requested by the config.
>>>>>> That causes many PMD to choose full-featured TX function,
>>>>>> which in many cases is much slower then one without offloads.
>>>>>> That patch adds checks to enabled extra HW offloads, only when
>>>>>> they were requested.
>>>>>> Plus it enables DEV_TX_OFFLOAD_IPV4_CKSUM,
>>>>>> only when other HW TX ofloads are going to be enabled.
>>>>>> Otherwise SW version of ip cksum calculation is used.
>>>>>> That allows to use vector TX function, when inline-ipsec is not
>>>>>> requested.
>>>>>>
>>>>>> Signed-off-by: Remy Horton <remy.horton at intel.com>
>>>>>> Signed-off-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
>>>>>> Acked-by: Radu Nicolau <radu.nicolau at intel.com>
>>>>>> ---
>>>>>>      examples/ipsec-secgw/ipsec-secgw.c | 44 +++++++++++++++--------
>>>>>>      examples/ipsec-secgw/ipsec.h       |  6 ++++
>>>>>>      examples/ipsec-secgw/sa.c          | 56 ++++++++++++++++++++++++++++++
>>>>>>      3 files changed, 91 insertions(+), 15 deletions(-)
>>>>>>
>>>>>> diff --git a/examples/ipsec-secgw/ipsec-secgw.c b/examples/ipsec-secgw/ipsec-secgw.c
>>>>>> index 1bc0b5b50..cfc2b05e5 100644
>>>>>> --- a/examples/ipsec-secgw/ipsec-secgw.c
>>>>>> +++ b/examples/ipsec-secgw/ipsec-secgw.c
>>>>>> @@ -208,8 +208,6 @@ static struct rte_eth_conf port_conf = {
>>>>>>      	},
>>>>>>      	.txmode = {
>>>>>>      		.mq_mode = ETH_MQ_TX_NONE,
>>>>>> -		.offloads = (DEV_TX_OFFLOAD_IPV4_CKSUM |
>>>>>> -			     DEV_TX_OFFLOAD_MULTI_SEGS),
>>>>> I believe this is disabling checksum offload for all cases and then
>>>>> enabling only for inline crypto and inline proto.
>>>> Yes.
>>>>
>>>>> This is breaking lookaside proto and lookaside none cases. Please
>>>>> correct me if I am wrong.
>>>> Why breaking?
>>> reduction in performance is kind of breaking the code.
>> I didn’t observe any performance drop with that patch.
>> In fact there was a tiny improvement (see below).
>> Did you see any regression with this patch on your HW?
> NXP hardware are low -end to mid end devices and we are always
> bottleneck by core cycles.
> So we would like to have as much offloads to HW as possible.
>>>> For cases when HW cksum offload is disabled, IPv4 cksum calculation
>>>> will be done in SW, see below:
>>>> prepare_tx_pkt(...)
>>>> {
>>>>       ...
>>>>        +
>>>>        +		/* calculate IPv4 cksum in SW */
>>>>        +		if ((pkt->ol_flags & PKT_TX_IP_CKSUM) == 0)
>>>>        +			ip->ip_sum = rte_ipv4_cksum((struct ipv4_hdr *)ip);
>>>>
>>>>
>>>> We tested lookaside-none case quite extensively - all works well,
>>>> in fact on Intel NICs it became even a bit faster because of that change
>>>> (though not much).
>>> yes, it may work well on one hardware, but may not perform good in other
>>> hardware where cores are limited.
>> Could you elaborate a bit more what do you mean by 'cores are limited' here?
> we have single core devices as well on which we run ipsec-secgw.
>> Do you mean that for some low end cpus calculating IPv4 cksum in SW is too expensive?
> yes, limited by core cycles and not by HW
>> Note that prepare_tx_pkts() and friends read/write L2/L3 packet headers anyway -
>> so IPv4 header will be in L1 cache already.
> Agreed, but still it will consume some cycles which are more than that
> of HW.
Impact will be lesser in lookaside none, but will be more in lookaside 
offload.
>>>> Disabling HW offloads when they are not really required has 2 benefits:
>>>>     1) allows app to be run on NICs without HW offloads support.
>>>>     2) allows dev_configure() for TX path to select simple/vector TX functions
>>>>         which for many NICs are significantly faster.
>>>>
>>>> Konstantin
>>>>
>>>>> So a NACK for this if my understanding is correct.
>>>>>



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