Adrian, Perhaps I wasn't as clear as I should have been. I'm not going to make any change that accounts for the amount of time a thread spends waiting for I/O. Rather, I want to re-expose a statistic which, on a per-CPU basis, lists the number of threads blocked in biowait().
-j On Wed, Oct 18, 2006 at 05:50:28PM -0700, adrian cockcroft wrote: > If you are going to fix it, could you add a microstate for iowait so > we have an accurate per process measure of blocked on diskio. I think > I filed a bug on this about 5 years ago or more... We already have a > microstate for page-in wait. > > Adrian > > On 10/18/06, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > >Adrian, > >biowait() still updates cpu_stats.sys.iowait. This means that Solaris > >is still keeping track of the number of threads that are blocked waiting > >for I/O. I see no reason not to expose this value to the user. > >I certainly do not intend to re-introduce a CPU percentage of time > >waiting for I/O, however. > > > >-j > > > > > >On Wed, Oct 18, 2006 at 05:37:15PM -0700, adrian cockcroft wrote: > >> The algorithm for iowait used to be something like: if idle and vmstat > >> b nonzero then iowait > >> So on Solaris 10, vmstat b is gone as well as iowait. If you want to > >> see how much time you are waiting for io, use iostat and add up the > >> times for each disk. > >> > >> Here is one way it was broken, a cpu starts an io, a different cpu > >> completes the io, which cpu was waiting? > >> > >> Adrian > >> > >> On 10/18/06, Mike Gerdts <[EMAIL PROTECTED]> wrote: > >> >On 10/18/06, adrian cockcroft <[EMAIL PROTECTED]> wrote: > >> >> In Solaris 10, iowait is no longer measured and will be reported as > >> >> zero by existing tools. Since iowait was always a variant of idle > >> >> time, this makes no difference to usr or sys time. > >> >> iowait was always a confusing and useless metric, which is why it was > >> >removed. > >> > > >> >On a related note, I have yet to see vmstat's "b" (kernel threads > >> >blocked on I/O) column be non-zero. This includes a large RAC > >> >environment where the previous measure of I/O health was (don't shoot > >> >the messenger!) iowait. The same workload on S9 consistently showed > >> >non-zero values in the "b" column. > >> > > >> >Has the meaning of this value changed as well, or is Solaris 10 just > >> >that much better at getting I/O out of the queue? > >> > > >> >TIA, > >> >Mike > >> > > >> >-- > >> >Mike Gerdts > >> >http://mgerdts.blogspot.com/ > >> > > >> _______________________________________________ > >> perf-discuss mailing list > >> perf-discuss@opensolaris.org > > > _______________________________________________ > perf-discuss mailing list > perf-discuss@opensolaris.org _______________________________________________ perf-discuss mailing list perf-discuss@opensolaris.org
