Hi Fiona
> -----Original Message----- > From: Trahe, Fiona <fiona.tr...@intel.com> > Sent: Tuesday, May 7, 2019 11:54 PM > To: Shally Verma <shal...@marvell.com>; dev@dpdk.org > Cc: akhil.go...@nxp.com; Ashish Gupta <ashi...@marvell.com>; Daly, Lee > <lee.d...@intel.com>; Sunila Sahu <ss...@marvell.com>; sta...@dpdk.org; > Trahe, Fiona <fiona.tr...@intel.com> > Subject: RE: [PATCH v2] doc/compress: clarify error handling on data-plane > > Hi Shally > > > > > > + > > > > > +There are some exceptions whereby errors can occur on the > > > ``enqueue``. > > > > > +For any error which can occur in a production environment and > > > > > +can be successful after a retry with the same op the PMD may > > > > > +return the error on the enqueue. > > > > This statement looks bit confusing. > > > > Seems like we are trying to add a description regarding op status > > > > check even after the enqueue call unlike current scenario, where > > > > app only check for it after dequeue? > > > [Fiona] The line following this explains that there is no need to > > > check op.status in this case. > > > Maybe it's not obvious that the application SHOULD check that all > > > ops are enqueued? > > > I can reword as: > > > The application should always check the value returned by the enqueue. > > > If less than the full burst is enqueued there's no need for the > > > application to check op.status of any or every op - it can simply > > > retry from the return > > > value+1 in a later enqueue and expect success. > > > > > I agree to purpose of patch but have these confusions when I read > description above: > > > > My understand is , if op status is INVALID_ARGS or any ERROR which is > > permanent in nature, Then nb_enqd return will be less than actually > passed. > [Fiona] True. > > > Regardless of whatever reason, if any time app gets nb_enqd < actually > > passed, then app should check status of nb_enqd + 1th op > [Fiona]. No, that's exactly what I was proposing to avoid. > > > to find exact cause of failure and then either attempt re-enqueue Or > > correct op preparation or take any other appropriate action. > [Fiona] I was proposing to constrain PMDs to only return a subset of errors > on the enqueue, so apps could be optimised. > But if you think it's not possible for PMDs to comply with it, then yes, apps > would always have to check status of nb_enqd + 1th op, and fork depending > on the status. > Is this the case? > If so, much of this patch is unnecessary and I'll send a simplified v3 as > almost > any status can be returned anywhere. > [Shally] Okay. I seem to understand it now. Purpose seem reasonable just a simpler rephrase would help. It will be easier for me to further feedback on 1st v2 patch sent. So will send it another email. > > > Also, STATUS_ERROR is very generic, it can be when queue is full in > > which case app can re-attempt an enqueue of same op > OR > > It can also indicate any irrecoverable error on enqueue, in which app > > just probably has to reset everything. For such kind of case, it might > > not be possible for PMD design to even push it into completion queue > > for an app to dequeue . I would suggest add another status code type > > which reflect permanent error condition i.e. irrecoverable error code > > which tells an app to perform PMD qp reset/re-init to recover and simplify > description just to state an expected APP behavior to avoid infinite loop > condition. > > It is then an app choice whether or not to check for op status for > > error after enqueue depending on whether its running in production > environment or dev environment. > [Fiona] I wouldn't expect ERROR in a queue full case. I'd see ERROR as the > catch-all when some other specific status isn't appropriate. If you think > there's a need for another specific status then best send an API patch > proposing it. This patch is only documenting the existing set. [Shally] Sorry, I missed. STATUS_NOT_PROCESSED can be indication of queue_full. STATUS_ERROR on dequeue = any catch-all error case STATUS_ERROR on enqueue = any irrecoverable error on op. app should not attempt same op or may be reset queue pair or PMD. Is this interpretation correct?
