[dpdk-dev] [PATCH] Adding RTE_KNI_PREEMPT configuration option

[Marc Sune]

On 11/02/15 02:54, Zhang, Helin wrote:
>
>> -----Original Message-----
>> From: Richardson, Bruce
>> Sent: Tuesday, February 10, 2015 9:24 PM
>> To: Marc Sune
>> Cc: dev at dpdk.org; Zhang, Helin
>> Subject: Re: [dpdk-dev] [PATCH] Adding RTE_KNI_PREEMPT configuration
>> option
>>
>> On Tue, Feb 10, 2015 at 12:59:29PM +0100, Marc Sune wrote:
>>> This patch of Nov 2014 hasn't been yet ACKed/NACKed. Could someone
>>> please give some quick feedback?
>>>
>>> Thanks
>>> marc
>>>
>>> On 07/11/14 12:00, Marc Sune wrote:
>>>> This patch introduces CONFIG_RTE_KNI_PREEMPT flag. When set to 'no',
>>>> KNI kernel thread(s) do not call schedule_timeout_interruptible(),
>>>> which improves overall KNI performance at the expense of CPU cycles
>> (polling).
>>>> Default values is 'yes', maintaining the same behaviour as of now.
>>>>
>>>> Signed-off-by: Marc Sune <marc.sune at bisdn.de>
>> Although a better option would be to have a runtime setting, this is still an
>> improvement over what we have.
>>
>> Acked-by: Bruce Richardson <bruce.richardson at intel.com>
>>
>>>> ---
>>>>   config/common_linuxapp                 |    1 +
>>>>   lib/librte_eal/linuxapp/kni/kni_misc.c |    4 ++++
>>>>   2 files changed, 5 insertions(+)
>>>>
>>>> diff --git a/config/common_linuxapp b/config/common_linuxapp index
>>>> 57b61c9..24b529d 100644
>>>> --- a/config/common_linuxapp
>>>> +++ b/config/common_linuxapp
>>>> @@ -380,6 +380,7 @@ CONFIG_RTE_LIBRTE_PIPELINE=y
>>>>   # Compile librte_kni
>>>>   #
>>>>   CONFIG_RTE_LIBRTE_KNI=y
>>>> +CONFIG_RTE_KNI_PREEMPT=y
>>>>   CONFIG_RTE_KNI_KO_DEBUG=n
>>>>   CONFIG_RTE_KNI_VHOST=n
>>>>   CONFIG_RTE_KNI_VHOST_MAX_CACHE_SIZE=1024
>>>> diff --git a/lib/librte_eal/linuxapp/kni/kni_misc.c
>>>> b/lib/librte_eal/linuxapp/kni/kni_misc.c
>>>> index ba77776..e7e6c27 100644
>>>> --- a/lib/librte_eal/linuxapp/kni/kni_misc.c
>>>> +++ b/lib/librte_eal/linuxapp/kni/kni_misc.c
>>>> @@ -229,9 +229,11 @@ kni_thread_single(void *unused)
>>>>   			}
>>>>   		}
>>>>   		up_read(&kni_list_lock);
>>>> +#ifdef RTE_KNI_PREEMPT
>>>>   		/* reschedule out for a while */
>>>>   		schedule_timeout_interruptible(usecs_to_jiffies( \
>>>>   				KNI_KTHREAD_RESCHEDULE_INTERVAL));
>>>> +#endif
>>>>   	}
>>>>   	return 0;
>>>> @@ -252,8 +254,10 @@ kni_thread_multiple(void *param)
>>>>   #endif
>>>>   			kni_net_poll_resp(dev);
>>>>   		}
>>>> +#ifdef RTE_KNI_PREEMPT
>>>>   		schedule_timeout_interruptible(usecs_to_jiffies( \
>>>>   				KNI_KTHREAD_RESCHEDULE_INTERVAL));
>>>> +#endif
>>>>   	}
>>>>   	return 0;
> As Bruce indicated, it would be better to do that at runtime, we can
> add a config in struct rte_kni_conf, which will be copied to
> struct rte_kni_device_info, then kernel space will know the configuration.
> This way, we can enable/disable PREEMPT during KNI instance allocation time.

As I said before, I see the point on having it at runtime and I agree.

However, rte_kni_device_info is a struct that is per interface, not for 
the entire KNI subsystem, so it is kind of abusing to add a flag there 
when only will be used once, at bootstrap. To do it "properly" we should 
create a new ioctl() call IMHO.

> Anyway, it can be done now or later.

So, do we integrate the current patch, as acked by Bruce before?

Marc
>
> Regards,
> Helin
>