On 3/20/2019 3:57 PM, Andrew Rybchenko wrote: > On 3/20/19 5:48 PM, Thomas Monjalon wrote: >> 19/03/2019 14:32, Yigit, Ferruh: >>> On 1/8/2019 11:30 AM, Tom Barbette wrote: >>>> Ferruh Yigit wrote: >>>>> Why timestamp offloading become useless? When timestamp offloading >>>>> enabled, >>>>> device fills 'mbuf.timestamp' and you can use it. >>>> But the frequency is unknown, and the reference time neither. So it can be >>>> used only to know that "some time passed" between packets. >>>> >>>>> For your case this timestamp for mlx is device clock and you are adding >>>>> this API >>>>> to be able to convert device clock to real time, this is not something >>>>> enables >>>>> the timestamp offload. >>>> I get your point, but a keyboard is highly required to use a computer. >>>> It's pretty much useless without it. Without this API, the timestamp >>>> offload makes no sense. It's a random number generator at best... >>>> >>>>> Technically driver can set the 'mbuf.timestamp' with the real clock >>>>> right, if it >>>>> is required? Or this can be defined by a devarg? >>>> I don't think so. Device have no sense of system time. And doing it in the >>>> driver is tricky because it depends on the user needs. Catch-up with NTP >>>> updates would need a timer and various parameters... Hence we prefer to >>>> give a simple working code, and users may do this if they want. >>>> >>>> >>>> For the other comments it's not my call... I would just underline that >>>> timestamp offload is not usable in the current state, and there is a lot >>>> of use case for monitoring latency-sensitive applications. >>> Hi Thomas, Andrew, >>> >>> CAn you please comment on patch, it adds a new 'rte_eth_read_clock()' API to >>> read device clock to read timestamp value, later to use this value to map >>> to the >>> actual time. >>> So that can convert timestamp information from each packet into real time. >> The approach is smart in my opinion. >> It is requesting the time generator (at its source) and allowing >> the app to do any kind of time handling strategy. >> >>> My question was if this is common requirement or specific to single device? >> It will work with any device providing some timestamps. >> There is nothing specific here in my opinion. >> >>> And if can be handles in driver level. >> Yes, it may be handled differently. >> But this approach looks to be the most flexible and reliable. >> >> Acked-by: Thomas Monjalon <tho...@monjalon.net> > > Taking into account that timestamp in mbuf is not normalized (neither > unit nor reference) and the API helps to normalize units, it makes sense. > I recall discussion about timestamp if should be normalized or > not, the decision was to keep it undefined. > > Acked-by: Andrew Rybchenko <arybche...@solarflare.com> >
Hi Tom, mlx patch doesn't apply cleanly, can you please send a new version on top of latest head? Thanks, ferruh
