[dpdk-dev] [PATCH v5 00/16] remove mbuf timestamp

Stephen Hemminger stephen at networkplumber.org
Tue Nov 3 18:42:36 CET 2020


On Tue, 03 Nov 2020 17:20:20 +0100
Thomas Monjalon <thomas at monjalon.net> wrote:

> 03/11/2020 17:08, Stephen Hemminger:
> > On Tue,  3 Nov 2020 15:09:15 +0100
> > Thomas Monjalon <thomas at monjalon.net> wrote:
> >   
> > > The mbuf field timestamp was announced to be removed for three reasons:
> > >   - a dynamic field already exist, used for Tx only
> > >   - this field always used 8 bytes even if unneeded
> > >   - this field is in the first half (cacheline) of mbuf
> > > 
> > > After this series, the dynamic field timestamp is used for both Rx and Tx
> > > with separate dynamic flags to distinguish when the value is meaningful
> > > without resetting the field during forwarding.  
> > 
> > There should be a place in documentation which describes all the
> > dynamic fields and their meaning.  For example, which drivers/features
> > set the field and the exact meaning.  
> 
> A dynamic field can be registered by anyone, including the apps.
> So you will never get a full list.
> The meaning of each field should be defined in its context
> (driver, lib or app).
> 
> > Is the timestamp in HW units, UTC units, or TSC ticks?  
> 
> The timestamp unit is driver-specific.
> It is explained in ethdev API:
> http://doc.dpdk.org/api/rte__ethdev_8h.html#a4346bf07a0d302c9ba4fe06baffd3196


Are there are any conventions we should use in this area?
There could be overlapping usage between subsystems?


More information about the dev mailing list