Sure, I saw what you proposed, but the real problem that we have is that machines get io-bound and we should have metrics in Solaris that tell us 1) a machine is io-bound, 2) which disks are responsible, and 3) which processes are being blocked
vmstat b is an approximation to the number of threads that are blocked, a microstate and dispay via prstat would let us see which threads are being blocked. There are even some unused slots in the microstate data structure, so it can be fixed without breaking backwards compatability. Adrian On 10/18/06, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
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
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