[ovs-dev] [PATCH v2] Make 100 percents packets sampled when sampling rate is 1.

Ben Pfaff blp at nicira.com
Wed Aug 5 18:24:10 UTC 2015


On Wed, Aug 05, 2015 at 10:01:26AM -0700, Justin Pettit wrote:
> 
> > On Aug 5, 2015, at 3:11 AM, Wenyu Zhang <wenyuz at vmware.com> wrote:
> > 
> > 
> >> On Aug 4, 2015, at 12:17 PM, Ben Pfaff <blp at nicira.com> wrote:
> >> 
> >> On Tue, Aug 04, 2015 at 04:05:58AM +0000, Wenyu Zhang wrote:
> >>> In ipfix and sflow, the sampling rate can be set as 1, which means
> >>> 100%.  And in order to make 100% packets sampled, I work out a patch
> >>> in datapath, which is for review on net-next.  And the same change
> >>> seems need to be added into lib/odp-execute.c too. Do you mean that it
> >>> is not necessary here?
> >> 
> >> I mean that we should modify the IPFIX and sFlow sampling code so that
> >> in the 0% and 100% sample rates cases it doesn't generate a sample
> >> action; there isn't any value in it.
> >> 
> >> This situation is a little different from the kernel situation, since we
> >> know exactly what actions can be fed to the userspace datapath in
> >> odp-execute.c, since the actions that it executes are generated by
> >> another part of the same source tree.  The kernel datapath, however,
> >> should be equally capable of handling actions from sources other than
> >> the Open vSwitch userspace.
> > 
> > It is OK that sample action shouldn’t be generated when the sampling
> > rate is 0%.  But I wonder why we shouldn’t generate sample action
> > when the sampling rate is 100%. It should happen in kernel datapth.
> > Or you means that the 100% sampling rate case won’t happen in the
> > userspace datapath?
> 
> Ben's on vacation, so I'll just have to guess what he meant.  I
> suspect his thinking was that you'd just call the actions that would
> be called through "sample" directly.  Since the run 100% of the time,
> there's no need to call them through the sample action.

Yes, that's what I meant.



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