Abdullah Aldahlawi wrote: > Greeting All > > I just wanna clarify basic concept about the two io probes (start) & > (wait-start). > > Does (wait-start) do the required data transfer specified in > args[0]->b_count right before the associated (wait-done) fires !! > > OR does the two associated probes (wait-start & wait-done) indicate a > waiting time period ONLY (without actual data transfer) in a busy I/O system.
Neither, really. Probes don't "do" anything related to the normal operation of the system, they only instrument it. wait-start fires when a wait-for-I/O is begun (I haven't looked, but I would assume at "biowait()" time, when the request has been submitted to the I/O hardware, and completion is pending). wait-done fires when the wait is terminated...i.e., when the system has completed the I/O. Indeed, dtrace -l -P io shows that wait-start and wait-done are both *in* the biowait() function, so I'm sure this is the case: http://cvs.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/os/bio.c#1210 > > Response appreciated ... > > > -- > This message posted from opensolaris.org > _______________________________________________ > dtrace-discuss mailing list > [email protected] _______________________________________________ dtrace-discuss mailing list [email protected]
