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

["Zhang, Helin" <helin.zhang@intel.com>]

> -----Original Message-----
> From: Richardson, Bruce
> Sent: Tuesday, February 10, 2015 9:24 PM
> To: Marc Sune
> Cc: dev@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@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@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.

Anyway, it can be done now or later.

Regards,
Helin