[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?
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