CMS output description

[Srinivas Ramakrishna]

Hi Venkat --

On Sun, Apr 14, 2013 at 12:43 PM,  <mndvenk at gmail.com> wrote:
> Ramki,
>
> It is great to see quick response.
>
> If the user time is too high comparatively to real time means is it short of resources also what I have observed my application certainly stopped more than 5 mins at the same time GC user time showing 3+ minutes.

The ratio of user:real is really a rough indicator of the level of
parallelism achieved by GC.
For the example you had below:-

>> Times: user=0.45 sys=0.00, real=0.09 secs

0.45/0.09 = 5 is the amount of parallelism in GC (of course not all of
that might be useful work, so
one can't with a straight face call it parallel speed-up, but still ...)

>
> I will send cpu details with GC logs tomorrow.

OK.

-- ramki

>
> Cheers,
> Venkat
> ------Original Message------
> From: Srinivas Ramakrishna
> To: Venkateswarlu Mandadi
> Cc: jdk6-dev at openjdk.java.net
> Subject: Re: CMS output description
> Sent: Apr 14, 2013 8:23 PM
>
> Hi Venkat --
>
> user: process virtual user time,
> sys: process-virtual system time
> real: elapsed time
>
> Re: "Use showing more than 3 mins" : depends on how many cpus you have.
>
> Really, what should typically concern you, as a user of GC, is the
> "real" time above, which is the duration for which your threads are
> stopped
> (when the time is associated with a stop-world pause). For concurrent
> ops, it's the end to end elapsed time for that cycle, so should not
> typically be of concern, as your application threads are running
> during that time.
>
> cheers.
> -- ramki
>
>
> On Sat, Apr 13, 2013 at 1:37 PM, Venkateswarlu Mandadi
> <mndvenk at gmail.com> wrote:
>> Hi,
>>
>> We are using CMS collector for oldgen (large heap -Xmx18g) and we have
>> observed there is a long whole world stop, in GC logs it was observed that
>> GC times are looking alright, but Times: Usr showing around more than 3
>> mins.
>>
>> Can someone explain Times fields
>>
>> Times: user=0.45 sys=0.00, real=0.09 secs
>>
>> Best Regards,
>>
>> Venkat
>
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