IDS Forum

Re: Mutex logs on logical log flip

Posted By: Art Kagel
Date: Monday, 29 February 2016, at 4:59 p.m.

In Response To: Re: Mutex logs on logical log flip (Fernando Nunes)

Neil:

Ignore the "threads" and just count the number of physical cores. You can
run up to 4 cpu vps per core on T5 chips. The problems with database
performance on the T* chipsets were not completelt solved until the T6 & T7
processors, but tbe T5s are far better than the T1-4 processors were.

Art

Art
On Feb 29, 2016 2:37 PM, "Fernando Nunes" <domusonline@gmail.com> wrote:

> I did take a look at the PMR... The number of CPU VPs was a bit of a
> shock...
> I've seen your other email.... I have some reservations regarding the fact
> that T5 has a lot of threads but not as much "internal pieces" so satisfy a
> real database process in each of those "threads". But you say you can't
> push it very hard without that... did you look at "onstat -g eff"? I'd be
> curious to see that, but i think there were some issues with the
> calculation on 11.50...
>
> Also, I have the feeling Art shared some thoughs about this in the
> past....?
>
> Regarding the number of connections... I do understand the
> recommendation... But you're on Solaris... and a few years ago after some
> deep investigation of some errors I've found some indicators that on
> Solaris, and related to the fact it uses TLI instead of sockets, this value
> is used to define the number of pending TCP requests on a specific port
> (something along these lines).
> But I suppose this wouldn't be related to your problem.... I can drop a
> note to Markus if I find this relevant.
> The only drawback of an high value is a bit more memory consumption that in
> an instance like this is most probably irrelevant.
>
> And I don't understand the rational behind the 36 poll threads... if each
> can handle 200-300 connections...15 should be a good value...
> On a previous situation I also got the feeling that too many poll threads
> wouldn't help...
>
> One very important thing.... do you have lots of new connections per second
> or not? This is typically THE trigger for the nsf.lock problem.
> Also.... do you have a large ready queue when this happens?
> Something I've seen for myself in the past was that occasionally the
> session holding the mutex got "stuck" in the ready queue if it get's too
> big....
> The CPU VP configuration may have impact on this. I'm afraid your "oninit"
> processes may be strugling for real CPU resources.
>
> As a final note, many years ago, a customer hitting a similar problem got a
> fix that basically changed the number of spins a thread would do before
> putting itself on hold waiting for a mutex. The argument was that in
> certain cases would be better to "waste" a few more CP cycles instead of
> going into the ready queue and struggle to "emerge" again.
> That would be a possible path... but it's such a sensitive area that I
> would not consider it until everything else was completely cleared.
>
> Still regarding the CPU and the "pushing the server hard".... be careful on
> how you measure this... it's better to measure the work done, and not the
> idle CPU....
>
> Finally, Spokey AFAIK left IBM and is wokring on his own... it's alive in
> facebook at least.
> Cosmo is still with us. AFAIK still with Informix. You may mention the
> previous history to Makus. Maybe he can shced some more light on this.
>
> On Mon, Feb 29, 2016 at 5:35 PM, NEIL TRUBY <neil.truby@ardenta.com>
> wrote:
>
> > Thanks. We already knew from Marco Greco, ex of IBM, that the handling of
> > this
> > in 11.70 is vastly imrpoved. This is the last large customer resisting
> that
> > move.
> >
> > VPCLASS CPU,NUM=230 # VPCLASS CPU - CPU #T5 Migration
> > NETTYPE tlitcp,11,800,NET
> >
> > .... are the settings. The server has 32 physical cores each with 8
> > threads.
> > 232 of these are assigned to this "Container" (ie VM).
> >
> > Typically we have 4,500 connections and IBM has suggested reducing the
> > number
> > of poll threads to 250 per tlitcp connection something like:
> >
> > NETTYPE tlitcp,36,250,NET
> > VPCLASS cpu,num=230,noage
> >
> > (NOAGE needs a Solaris change to work)
> >
> >
> >
> >
>
> *******************************************************************************
> > Forum Note: Use "Reply" to post a response in the discussion forum.
> >
> >
>
> --
> Fernando Nunes
> Portugal
>
> http://informix-technology.blogspot.com
> My email works... but I don't check it frequently...
>
> --001a113f3bd4a535c2052cedc450
>
>
>
> *******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>

--047d7bea43fcabc3f5052cefc26b

Messages In This Thread

• Mutex logs on logical log flip
  NEIL TRUBY -- Sunday, 28 February 2016, at 6:28 p.m.
  • Re: Mutex logs on logical log flip
    Art Kagel -- Sunday, 28 February 2016, at 6:46 p.m.
    • Re: Mutex logs on logical log flip
      NEIL TRUBY -- Sunday, 28 February 2016, at 6:54 p.m.
      • Re: Mutex logs on logical log flip
        Art Kagel -- Sunday, 28 February 2016, at 6:57 p.m.
        • Re: Mutex logs on logical log flip *NM*
          NEIL TRUBY -- Sunday, 28 February 2016, at 7:12 p.m.
        • Re: Mutex logs on logical log flip
          Fernando Nunes -- Sunday, 28 February 2016, at 7:54 p.m.
          • Re: Mutex logs on logical log flip
            Madison Pruet -- Sunday, 28 February 2016, at 9:05 p.m.
          • Re: Mutex logs on logical log flip
            Fernando Nunes -- Monday, 29 February 2016, at 4:53 a.m.
          • Re: Mutex logs on logical log flip
            NEIL TRUBY -- Monday, 29 February 2016, at 12:35 p.m.
            • Re: Mutex logs on logical log flip
              Madison Pruet -- Monday, 29 February 2016, at 12:52 p.m.
              • Re: Mutex logs on logical log flip
                NEIL TRUBY -- Monday, 29 February 2016, at 1:09 p.m.
                • Re: Mutex logs on logical log flip
                  John Miller iii -- Monday, 29 February 2016, at 3:59 p.m.
                  • Re: Mutex logs on logical log flip
                    NEIL TRUBY -- Monday, 29 February 2016, at 7:41 p.m.
                    • Re: Mutex logs on logical log flip
                      Madison Pruet -- Monday, 29 February 2016, at 9:27 p.m.
                    • Re: Mutex logs on logical log flip
                      RICHARD KOFLER -- Tuesday, 1 March 2016, at 3:37 a.m.
                • Re: Mutex logs on logical log flip
                  Spokey Wheeler -- Tuesday, 1 March 2016, at 4:18 a.m.
            • Re: Mutex logs on logical log flip
              Fernando Nunes -- Monday, 29 February 2016, at 2:36 p.m.
              • Re: Mutex logs on logical log flip
                Art Kagel -- Monday, 29 February 2016, at 4:59 p.m.

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