IDS Forum

Re: cpu time

Posted By: Michael Mueller
Date: Tuesday, 27 May 2003, at 3:38 a.m.

In Response To: RE: cpu time (Quanta Infxlist)

I am not sure how to explain that. It's just 2 cpus and what happens
depends on scheduling and timing details. Some minor change in your
application or in the online server might be responsible for this.

With 9.30.UC3 on an 8 cpu Solaris8 machine with 8 cpu vps and this
client started 3 times:

while :
do
dbaccess sysmaster <<eof >/dev/null 2>&1
select count(*) from syscolumns a, syscolumns b;
eof
done

i got this:

Individual virtual processors:
vp pid class usercpu syscpu total
1 17027 cpu 6.08 0.00 6.08
2 17028 adm 0.00 0.00 0.00
3 17029 cpu 78.30 0.00 78.30
4 17030 cpu 72.06 0.00 72.06
5 17031 cpu 76.67 0.01 76.68
6 17032 cpu 4.49 0.00 4.49
7 17033 cpu 0.00 0.00 0.00
8 17034 cpu 0.00 0.00 0.00
9 17035 cpu 0.00 0.00 0.00
10 17036 lio 0.00 0.00 0.00
11 17037 pio 0.00 0.00 0.00
12 17038 aio 0.00 0.00 0.00
13 17039 msc 0.01 0.00 0.01
14 17040 tli 0.00 0.00 0.00
tot 237.61 0.01 237.62

The funny thing in this example is that my threads avoid running on cpu 1.


Quanta Infxlist wrote:
> Our 9.30 on an under-used machine has 2 CPUVP's (and 2 CPU's). The
use is
> relatively even. On the same server 7.31 (was upgraded) the use of each
> oninit was very uneven.
>
> MW
>
>
>>-----Original Message-----
>>From: Michael Mueller [mailto:michael.mueller@kay-mueller.de]
>>Sent: Monday, 26 May 2003 6:12 p.m.
>>To: ids@iiug.org
>>Cc: Mark Scranton; ifxmaillist@quanta.co.nz
>>Subject: Re: cpu time [1196]
>>
>>
>>I don't think this has changed in 7.3. Ifxmaillist@quanta.co.nz do you
>>have any indication for that?.
>>
>>It's perfectly normal and I think it's even desirable. If less oninit
>>processes can handle the workload, the os and memory cache
>>overhead may
>>be less.
>>
>>Don't forget that vps are processes, not physical cpus. Even
>>if you bind
>>vps to cpus, this does (hopefully, may depend on how it's
>>done) not mean
>>that the cpu does not run anything else even if it's bound
>>oninit goes idle.
>>
>>The reason for this behavior is the scheduling algorithm used
>>by online.
>>If a thread becomes runnable and some vps are idle, the
>>scheduler tends
>>to wake up the vp with the lowest number.
>>
>>What I think is critical in this context is a situation where all vps
>>are busy with non empty ready queues, but the overall usage per second
>>is much less then NUMCPUVPS seconds (if you have external
>>poll vps etc.
>>with a high cpu usage you have to count these too). This should not
>>happen (but it has). If it does, you can add more cpu vps
>>than you have
>>cpus. But you also should talk to support because its a
>>performance bug.
>>
>>
>>Michael
>>
>>
>>
>>
>>
>>Mark Scranton wrote:
>> > I have always felt that IDS doesn't attempt to load
>>balance work assigned
>> > to CPUVPS (or other VPS for that matter). The observation
>>you are seeing
>> > (some CPUVPS "busier" than others) has been true since
>>early v7. We don't
>> > do scheduling, pre-emption, or time-slicing. Threads will
>>sit in a ready
>> > queue until a yielding thread grabs it off, switches the
>>context(s), and
>> > now the new thread runs.
>> >
>> > Anyone else?
>> >
>> > HTH -
>> > Mark
>> >
>> > Mark Scranton
>> > Principal Consultant/Teacher
>> > IBM Denver
>> >
>> > IBM Software Group - Data Management
>> > Office: 303-773-5067
>> > Cell: 303-929-0914
>> > email: mscranto@us.ibm.com
>> >
>> >
>> >
>> >
>> >
>>
>>
>>--
>>
>>=== Michael Mueller ==================
>>Tel. + 49 8171 63600
>>Fax. + 49 8171 63615
>>Web: http://www.mm.kay-mueller.de
>> http://www.planets.kay-mueller.de
>>======================================
>>
>>
>
>
>
>


--

=== Michael Mueller ==================
Tel. + 49 8171 63600
Fax. + 49 8171 63615
Web: http://www.mm.kay-mueller.de
http://www.planets.kay-mueller.de
======================================

Messages In This Thread

• cpu time
  EML -- Tuesday, 20 May 2003, at 1:46 p.m.
  • Re: cpu time
    rkusenet -- Tuesday, 20 May 2003, at 2:07 p.m.
  • Re: cpu time
    John Bejarano -- Tuesday, 20 May 2003, at 3:19 p.m.
  • Re: cpu time
    Mark Scranton -- Wednesday, 21 May 2003, at 11:03 a.m.
    • RE: cpu time
      Quanta Infxlist -- Wednesday, 21 May 2003, at 10:21 p.m.
    • Re: cpu time
      Michael Mueller -- Monday, 26 May 2003, at 2:14 a.m.
    • Re: cpu time
      Michael Mueller -- Monday, 26 May 2003, at 4:09 a.m.
    • RE: cpu time
      Quanta Infxlist -- Monday, 26 May 2003, at 4:14 p.m.
      • Re: cpu time
        Michael Mueller -- Tuesday, 27 May 2003, at 3:38 a.m.

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