On Tue, Jun 02, 2015 at 10:35:24AM -0400, Doug Ledford wrote: > So, just so everyone is clear on this point: the current user space > implementation of this feature creates an unversioned, newly named > ibv_wc_ex struct that is ibv_wc with a 64bit timestamp tacked on at the > end (not 64bit aligned either). If we ever wanted to have a different > extension to our ibv_wc struct, there is no good way to do that. No, if they followed (I didn't check yes) the extension scheme then the poll call is struct ibv_wc_ex wcs[num_wcs] ibv_poll_wc_ex(&wcs,num_wcs,sizeof(wcs[0])); And the drivers decide what to do based on the 3rd argument, which is essentially the ABI version. > Jason, when the XRC and flow steering extensions were added to > libibverbs, you complained loudly that they were not added in the agreed > upon format and cited a previous on list discussion. Do you have a link > to that discussion? Not off hand, but that was different, that was a misuse of comp_mask, IIRC. Or, the question in my mind based on looking at the UAPI patches is what things should be driver private and what should be general. Broadly my thoughts: - 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. - 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. This is suggesting to me these details really are not general. - There should be much better definition on what all this stuff is, units for frequency? When is the timestamp applied? - Should an app even be exposed to mask? This is very difficult to use correctly in the general case. Only cases where an app is restarted more often than a wrap period are trivial to use properly. Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
