On Wed, Jun 03, 2015 at 10:48:28PM +0300, Or Gerlitz wrote: > > - Should the frequency and mask be general, or driver private? If the > > cycles->ns conversion is a function they should be driver private. > > Even if they are general at libibverbs, they don't *have* to be in > > the kernel's general query response. > > If they are general in libibverbs, what's the point not to put them in > the kernel's general query response?
If there is a timestamp_to_ns API then they would not be general in libiverbs either. > > - Should frequency even be frequency? Most clocks are expressed > > accurately as a period in picoseconds. Frequency is more often > > imprecise. (eg ethernet is 3200 ps or 312.5MHz) > > However FDR/EDR is fractional for both (4693.33333333 ps vs > > 213.0681818181818 MHz) > > Precision is very important for time conversions, so a > > multiply-divide scheme would be ideal. > > From Christoph's response I got the impression that our proposal of > exposing frequency and mask combined with raw time stamps excellently > fits typical user needs, so I thought we're good. Doug made a comment > that things look OK to him and the rest of the work would be when we > come to review the user-space patches. This response ignores my point about precision. MHz is fine *for mlx hardware* but someone elses hardware that uses, say 312.5 MHz (ie the ethernet symbol clock) is NOT OK because MHz looses too much precision. Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
