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Re: Latch spin - OS timeslice

From: Kyle <kyle_at_gadgets.co.nz.nospam>
Date: Thu, 28 Mar 2002 19:02:19 +1200
Message-ID: <rczo8.89$Og6.4315@news02.tsnz.net>


Hi,

I'd be interested in looking at the mpstat output for all processors. You should notice a higher smtx count for proc 0 being the master may be higher. But, a count of 100 is not a problem from what I have seen.

Is the sys time from vmstat greatly higher than the user time?

What does the mpstat column srw indicate. Is it a lot higher than the smtx col?

Unfortunately I am not near a sun machine as I have been working on NT for a bit now, but from memory, the lockstat command "man lockstat" will dump all lock contention for you.

I would be very interested in seeing both the output of this and the output of mpstat for the same run. Lockstat, again from memory will need to have flags set as it dumps everything(???)

Regards,
Kyle
www.gadgets.co.nz

"Yong Huang" <yong321_at_yahoo.com> wrote in message news:b3cb12d6.0203272159.41c4fbc0_at_posting.google.com...
> Here's one puzzle to me. Take my Solaris 2.6 on sun4u 8 CPUs as an
> example. mpstat tells me the number of spins on mutexes (smtx column)
> per second on one processor is way below 100. Maybe this is at night.
> But I can't see a number higher than 100 no matter what I do in the
> database or through my Portal site which is notorious for library
> cache latch contention (my _spin_count is 2000). ps -cL tells me the
> foregroup and background oracle processes are at TS class priority
> ranging from 8 to 46. dispadmin -c TS -g tells me that their time
> quantum ranges between 40 to 200 ms. I would imagine that time slice
> is more than enough for 2000 spins. Why does mpstat show such a low
> number?
>
> Since this is an Oracle group, can anyone tell me how to trigger
> oracle process spins? I know when I access an Oracle Portal page,
> usually more than 1 session will be waiting for "latch free"
> (latch#106) for several seconds! Maybe I'll wait till 10am and
> possibly set _spin_count to 10000 or higher.
>
> Yong Huang
>
> alexbrds_at_yahoo.com (Alex Bardos) wrote in message
news:<f5e30250.0203251807.92e1747_at_posting.google.com>...
> > time slice. I would expect the whole SPIN cycle to be comparable to
> > the time slice, still smaller though to increase chances of not being
> > preempted by the OS after the time slice is up.
Received on Thu Mar 28 2002 - 01:02:19 CST

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