Shared mem connections and semaphores

Please help me to interpret the output of onstat -g sch. If I see busy waits and spins/wait that are not zero, does this mean I have too few semaphores configured on my server? I am running Unixware with IDS 7.3.1.ud5. I have followed the tunning guides recommendations and have been a bit more generous that indicated, but I want to be sure I have enough semaphores allocated to meet my user load. Thanks Tim Bragg. PS: In general, I understand what the counters in the onstat output are, but I can find very little guidance on how to interpret those numbers, e.g. what is the expected results for a well tuned system, how can I affect the counts (up or down) to achieve better performance. Is there any document out there that explains well the interpretation of the outputs from the onstat command and how to use that info to tune. I have read the performance guide on the IBM web site for IDS 7.x, but the guidance there is pretty limited in how to interpret the output.

no - busy waits and spin waits are not associated with kernel semaphores. "Tim Bragg" <braggtim@pentama To: ids@iiug.org tion.com> cc: Sent by: Subject: Shared mem connections and semaphores [976] forum.subscriber@ iiug.org 04/23/2003 08:45 AM Please help me to interpret the output of onstat -g sch. If I see busy waits and spins/wait that are not zero, does this mean I have too few semaphores configured on my server? I am running Unixware with IDS 7.3.1.ud5. I have followed the tunning guides recommendations and have been a bit more generous that indicated, but I want to be sure I have enough semaphores allocated to meet my user load. Thanks Tim Bragg. PS: In general, I understand what the counters in the onstat output are, but I can find very little guidance on how to interpret those numbers, e.g. what is the expected results for a well tuned system, how can I affect the counts (up or down) to achieve better performance. Is there any document out there that explains well the interpretation of the outputs from the onstat command and how to use that info to tune. I have read the performance guide on the IBM web site for IDS 7.x, but the guidance there is pretty limited in how to interpret the output.

HeadingDescriptionFormatvpThe virtual processor ID.DecpidThe system process ID for the process running this virtual processor.DecclassThe class of virtual processor.StrsemopsThe number of times this virtual procesor went idle and performed a semaphore operation to wait for work.Decbusy waitsThe number of times the virtual processor found no work to do and spun to avoid going to sleep on a semaphore.Decspins/waitThe average number of spins that were performed for each busy wait.Dec Notes The number of spins performed during a busy wait is platform dependent. Busy waits allow a virtual processor to avoid a context switch while waiting for additional work to show up in the ready queues. Spins/wait is calculated as (spins * 10,000) / busy waits. Busy waits only occur when the configuration parameter MULTIPROCESSOR is set to a value other than 0. --- Tim Bragg <braggtim@pentamation.com> wrote: > Please help me to interpret the output of > onstat -g sch.> > If I see busy waits and spins/wait that are not > zero, does this mean I > have too few semaphores configured on my > server? > > I am running Unixware with IDS 7.3.1.ud5. I > have followed the tunning > guides recommendations and have been a bit more > generous that indicated, > but I want to be sure I have enough semaphores > allocated to meet my user > load. > > Thanks > Tim Bragg. > > PS: In general, I understand what the counters > in the onstat output > are, but I can find very little guidance on how > to interpret those > numbers, e.g. what is the expected results for > a well tuned system, how > can I affect the counts (up or down) to achieve > better performance. Is > there any document out there that explains well > the interpretation of > the outputs from the onstat command and how to > use that info to tune. I > have read the performance guide on the IBM web > site for IDS 7.x, but the > guidance there is pretty limited in how to > interpret the output. > > Saludos Oscar Hernández Molina --------------------------------- Do you Yahoo!? The New Yahoo! Search - Faster. Easier. Bingo.