RE: Tomcat memory

[Gokul . Baskaran]

Andre,

Thanks for getting granular. Let me explain to the items which could have 
sounded to be confusing..

The JVM in discussion is Oracle JVM.

OS is the 64bit Windows 2012. - OS has 6GB - OS should not impose a limit on 
memory (Only in this specific case, as OS is 64bit and total amount of memory 
available is 6GB) unless the memory consumption by other processes does not get 
impacted or grows near 5GB - 6GB limit.

>From my earlier posts ---

i. It is a Tomcat / Application question as well, as memory default can 
be configured in the application config. - Big typo error, it should have been 
Cannot be configured.
ii. Thanks again, to make things clear. When I meant default, what is 
the default min and max that is given to an application if there nothing 
defined in the JVM ? - I meant the JVM heap memory   given to the 
application, which is configured in the tomcat instance.
 
With respect to the Oracle documentation, if the -Xms and Xmx are not set. The 
max will be set to 1/4th which is around 1.5GB of 6 GB   .

To your point on "There is no Tomcat-Level configuration option" - If I have 2 
tomcat instance on the same OS (Tomcat 1 and Tomcat 2). I can define Xms and 
Xmx in catalina.sh or setenv.sh in each of the tomcat instances. For example, 
if Tomcat 1 is configured to have 1GB, JVM heap size for Tomcat 1 will have 1GB 
and if Tomcat 2 is configured to 2 GB, then JVM heap size for Tomcat 2 will get 
2GB.

Yes, it is clear and thanks for explaining.

-Gokul


-Original Message-
From: André Warnier (tomcat) [mailto:a...@ice-sa.com] 
Sent: Monday, February 22, 2016 8:37 AM
To: users@tomcat.apache.org
Subject: Re: Tomcat memory

On 22.02.2016 13:02, Gokul.Baskaran wrote:
> The answer I expected is the JVM grows as much as to the available system 
> memory of there are m min and max set.
>

Gokul,

Well, no.

And because these messages get archived and searched later by other people, 
they may get the wrong conclusion and therefore I will try again.

Re-read your last question.
And then re-read your question before that one.
And then re-read your question before that one.

The problem here is not that you are not being given the information that you 
want.
The problem is that each time you ask your question, you ask it in a different 
way, and each time somehow in a way that confuses people as to what exactly you 
want to know.
And the reason why it is confusing is that in your succesive questions you keep 
on talking about "application memory" in various ways, but it is not clear what 
you are referring to as "application".
For the OS, the JVM is an application.
For the JVM, Tomcat is the application.
And for Tomcat, the web applications (webapps) are the applications.

The JVM is one process that is running on a machine, under an OS.
That OS probably imposes limits on how much resources (including memory) a 
given process is allowed to use.  If a process tries to use more than this, it 
will be killed with an "out of memory" error.  It is unlikely that this 
per-process limit is "the available system memory". The OS will kill the 
process before it uses all of that.

The JVM itself (of which there are various models on the market) uses memory in 
various ways, for various purposes.  One of these purposes is to manage a Heap, 
which it makes available to Java applications which run inside the JVM.
But the JVM also uses memory for other reasons, such as a stack, and for the 
code of the JVM itself.

For any given JVM, there are (probably) parameters which tell the JVM how much 
memory it should set aside initially for the Heap, and then also for how big it 
should let the Heap grow as a maximum.  For the Oracle JVMs, these parameters 
are "-Xms" and "-Xmx".
By default (if these parameters are not set), the JVM uses some default values, 
which /vary/ depending on the specific JVM and on the circumstances under which 
it is running (the total available machine memory, for example).
For the Oracle JVM, someone already quoted to you the relevant documentation.
For other JVM's, you need to look at the relevant JVM documentation.
(You never indicated which JVM you are using).

The JVM runs java applications (of which Tomcat - the whole Tomcat - is one).  
These Java applications cannot set the amount of memory that they will use in 
the Heap of the JVM, other than indirectly (if they are well-written, the 
minimum necessary; if they are not well-written, who knows).  There is no 
Tomcat-level configuration option, that allows one to set how much Heap space 
Tomcat can use within the JVM Heap.

Then within Tomcat, there are "web applications" running.  Individual web 
applications also cannot set how much Heap they will use, because is not 
"their" Heap, it is the "Tomcat Heap", which itself is not really the Tomcat 
Heap, it is the JVM's Heap.
That Heap is used by /all/ web applications at the same time.
(That is a bit of an approximation, but ultimately it boils 

RE: Tomcat memory

[Gokul . Baskaran]

I meant the expectation as what I understood from the earlier posts.

The hyperlink url was not formed correct, hyperlink url helped as well. Earlier 
I read it as the 1/64th and 1/4th applied only to the JSE5.

Thanks to Olaf. 

-Gokul


-Original Message-
From: David kerber [mailto:dcker...@verizon.net] 
Sent: Monday, February 22, 2016 6:46 AM
To: Tomcat Users List 
Subject: Re: Tomcat memory

On 2/22/2016 7:02 AM, Gokul.Baskaran wrote:
> The answer I expected is the JVM grows as much as to the available system 
> memory of there are m min and max set.

But if you go back and read what others have posted, you will find that that is 
not the case.  Just because that's what you expect, does not mean that is what 
is actually going to happen.


>
> -Gokul
>
> Sent from iPhone
>
>> On Feb 22, 2016, at 2:43 AM, André Warnier (tomcat)  wrote:
>>
>>> On 22.02.2016 03:44, Gokul.Baskaran wrote:
>>> Thanks again, to make things clear. When I meant default, what is the 
>>> default min and max that is given to an application if there nothing 
>>> defined in the JVM ?
>>
>> In how many different ways do you need to be told this ?
>> Re-read the previous answers that you already received.  All the information 
>> is there.
>>
>>> In my case, the Tomcat is running on windows and I don't have 
>>> setenv.bat or sentenv.sh or even catalina.bat and catalina.conf does 
>>> not have the OPT config for min and max. HTH
>>>
>>> Thank you
>>>
>>> -Gokul
>>>
>>>
>>> -Original Message-
>>> From: Olaf Kock [mailto:tom...@olafkock.de]
>>> Sent: Sunday, February 21, 2016 3:04 PM
>>> To: Tomcat Users List 
>>> Subject: Re: Tomcat memory
>>>
>>> grep mx bin/* found only settings in setenv.sh in my installation - this 
>>> lets me state that there are no defaults: setenv.sh is not contained in the 
>>> distribution but will be read in case it's found in the file system.
>>> Thus there's no tomcat default that I'm aware of. Anybody who distributes 
>>> tomcat with a setenv.sh might have a sensible default for their embedded 
>>> application, but the raw distribution AFAIK has none.
>>>
>>> Safe assumption should be: Whatever the JVM thinks is appropriate is the 
>>> default.
>>>
>>> Create a setenv.sh or setenv.bat and set CATALINA_OPTS to the desired 
>>> value, e.g. "-Xms 2048m -Xmx2048m" (but there will probably be more 
>>> settings, e.g. for tuning the garbage collector...
>>>
>>> (apologies in case this goes out after the problem has long been solved:
>>> I'm in a hotel that blocks SMTP and have to find a way to send mail 
>>> from
>>> here)
>>>
>>> Olaf
>>>
 Am 21.02.2016 um 18:23 schrieb Gokul.Baskaran:
 Question was for Java 7

 It is a Tomcat / Application question as well, as memory default can be 
 configured in the application config.

 I totally agree that the best practice is to set the Xms and -Xmx. As am 
 going to change the config, I would curious to know if the tomcat ui or 
 the catalina does not have a Xms and -Xmx, would it default to 400MB? I 
 read this in another forum.

 -Gokul


 -Original Message-
 From: Olaf Kock [mailto:tom...@olafkock.de]
 Sent: Sunday, February 21, 2016 3:14 AM
 To: Tomcat Users List 
 Subject: Re: Tomcat memory

 This is rather a Java than a tomcat question:

 The JVM allocates memory based on whatever default your current JVM 
 version decides (you don't mention what version of Java you're on)

  From a text on
 http://docs.oracle.com/javase/7/docs/technotes/guides/vm/gc-ergonom
 ics
 .html
 that's linked from my Java's manpage:

  *initial heap size*

  Larger of 1/64th of the machine's physical memory on the machine
  or some reasonable minimum. Before J2SE 5.0, the default initial
  heap size was a reasonable minimum, which varies by platform.
  You can override this default using the |-Xms| command-line 
 option.

  *maximum heap size*

  Smaller of 1/4th of the physical memory or 1GB. Before J2SE 5.0,
  the default maximum heap size was 64MB. You can override this
  default using the |-Xmx| command-line option.

  *Note:* The boundaries and fractions given for the heap size are
  correct for J2SE 5.0. They are likely to be different in subsequent
  releases as computers get more powerful.

 Note that this is from JavaSE7 and even mentions 5 - with more power there 
 comes more initial and maximum memory defaults.

 I'm not aware of the actual development of the default memory - 
 mostly because I consider it good practice to know what an 
 application uses and provide it explicitly, rather than relying on 
 defaults. (and frankly, on the applications that I see, the 

Re: Tomcat memory

[Gokul . Baskaran]

The answer I expected is the JVM grows as much as to the available system 
memory of there are m min and max set.

-Gokul

Sent from iPhone

> On Feb 22, 2016, at 2:43 AM, André Warnier (tomcat)  wrote:
> 
>> On 22.02.2016 03:44, Gokul.Baskaran wrote:
>> Thanks again, to make things clear. When I meant default, what is the 
>> default min and max that is given to an application if there nothing defined 
>> in the JVM ?
> 
> In how many different ways do you need to be told this ?
> Re-read the previous answers that you already received.  All the information 
> is there.
> 
>> In my case, the Tomcat is running on windows and I don't have setenv.bat or 
>> sentenv.sh or even catalina.bat and catalina.conf does not have the OPT 
>> config for min and max. HTH
>> 
>> Thank you
>> 
>> -Gokul
>> 
>> 
>> -Original Message-
>> From: Olaf Kock [mailto:tom...@olafkock.de]
>> Sent: Sunday, February 21, 2016 3:04 PM
>> To: Tomcat Users List 
>> Subject: Re: Tomcat memory
>> 
>> grep mx bin/* found only settings in setenv.sh in my installation - this 
>> lets me state that there are no defaults: setenv.sh is not contained in the 
>> distribution but will be read in case it's found in the file system.
>> Thus there's no tomcat default that I'm aware of. Anybody who distributes 
>> tomcat with a setenv.sh might have a sensible default for their embedded 
>> application, but the raw distribution AFAIK has none.
>> 
>> Safe assumption should be: Whatever the JVM thinks is appropriate is the 
>> default.
>> 
>> Create a setenv.sh or setenv.bat and set CATALINA_OPTS to the desired value, 
>> e.g. "-Xms 2048m -Xmx2048m" (but there will probably be more settings, e.g. 
>> for tuning the garbage collector...
>> 
>> (apologies in case this goes out after the problem has long been solved:
>> I'm in a hotel that blocks SMTP and have to find a way to send mail from
>> here)
>> 
>> Olaf
>> 
>>> Am 21.02.2016 um 18:23 schrieb Gokul.Baskaran:
>>> Question was for Java 7
>>> 
>>> It is a Tomcat / Application question as well, as memory default can be 
>>> configured in the application config.
>>> 
>>> I totally agree that the best practice is to set the Xms and -Xmx. As am 
>>> going to change the config, I would curious to know if the tomcat ui or the 
>>> catalina does not have a Xms and -Xmx, would it default to 400MB? I read 
>>> this in another forum.
>>> 
>>> -Gokul
>>> 
>>> 
>>> -Original Message-
>>> From: Olaf Kock [mailto:tom...@olafkock.de]
>>> Sent: Sunday, February 21, 2016 3:14 AM
>>> To: Tomcat Users List 
>>> Subject: Re: Tomcat memory
>>> 
>>> This is rather a Java than a tomcat question:
>>> 
>>> The JVM allocates memory based on whatever default your current JVM
>>> version decides (you don't mention what version of Java you're on)
>>> 
>>> From a text on
>>> http://docs.oracle.com/javase/7/docs/technotes/guides/vm/gc-ergonomics
>>> .html
>>> that's linked from my Java's manpage:
>>> 
>>> *initial heap size*
>>> 
>>> Larger of 1/64th of the machine's physical memory on the machine
>>> or some reasonable minimum. Before J2SE 5.0, the default initial
>>> heap size was a reasonable minimum, which varies by platform.
>>> You can override this default using the |-Xms| command-line option.
>>> 
>>> *maximum heap size*
>>> 
>>> Smaller of 1/4th of the physical memory or 1GB. Before J2SE 5.0,
>>> the default maximum heap size was 64MB. You can override this
>>> default using the |-Xmx| command-line option.
>>> 
>>> *Note:* The boundaries and fractions given for the heap size are
>>> correct for J2SE 5.0. They are likely to be different in subsequent
>>> releases as computers get more powerful.
>>> 
>>> Note that this is from JavaSE7 and even mentions 5 - with more power there 
>>> comes more initial and maximum memory defaults.
>>> 
>>> I'm not aware of the actual development of the default memory - mostly
>>> because I consider it good practice to know what an application uses
>>> and provide it explicitly, rather than relying on defaults. (and
>>> frankly, on the applications that I see, the default typically is not
>>> even enough - let alone a good basis for tuning)
>>> 
>>> While we're at it: For production systems I consider it good practice to 
>>> set -Xms and -Xmx to the same value. Reason: If you don't have enough 
>>> memory available, you want to know this when the process starts, not days 
>>> later when it tries to allocate "the rest" - typically sunday night at 3am.
>>> 
>>> Olaf
>>> 
 Am 21.02.2016 um 03:39 schrieb Gokul.Baskaran:
 Hi,
 
 I am currently running tomcat 7 in Windows 2012.
 
 The current JVM Heap memory parameters are set to empty, does the JVM Heap 
 memory utilize the entire memory of the OS or does it default to a 
 specific memory number?
 
 Thank you
 -Gokul
>>> 
>>> 

RE: Tomcat memory

[Gokul . Baskaran]

Thanks again, to make things clear. When I meant default, what is the default 
min and max that is given to an application if there nothing defined in the JVM 
?

In my case, the Tomcat is running on windows and I don't have setenv.bat or 
sentenv.sh or even catalina.bat and catalina.conf does not have the OPT config 
for min and max. HTH

Thank you

-Gokul


-Original Message-
From: Olaf Kock [mailto:tom...@olafkock.de] 
Sent: Sunday, February 21, 2016 3:04 PM
To: Tomcat Users List 
Subject: Re: Tomcat memory

grep mx bin/* found only settings in setenv.sh in my installation - this lets 
me state that there are no defaults: setenv.sh is not contained in the 
distribution but will be read in case it's found in the file system.
Thus there's no tomcat default that I'm aware of. Anybody who distributes 
tomcat with a setenv.sh might have a sensible default for their embedded 
application, but the raw distribution AFAIK has none.

Safe assumption should be: Whatever the JVM thinks is appropriate is the 
default.

Create a setenv.sh or setenv.bat and set CATALINA_OPTS to the desired value, 
e.g. "-Xms 2048m -Xmx2048m" (but there will probably be more settings, e.g. for 
tuning the garbage collector...

(apologies in case this goes out after the problem has long been solved:
I'm in a hotel that blocks SMTP and have to find a way to send mail from
here)

Olaf

Am 21.02.2016 um 18:23 schrieb Gokul.Baskaran:
> Question was for Java 7
>
> It is a Tomcat / Application question as well, as memory default can be 
> configured in the application config. 
>
> I totally agree that the best practice is to set the Xms and -Xmx. As am 
> going to change the config, I would curious to know if the tomcat ui or the 
> catalina does not have a Xms and -Xmx, would it default to 400MB? I read this 
> in another forum. 
>
> -Gokul
>
>
> -Original Message-
> From: Olaf Kock [mailto:tom...@olafkock.de]
> Sent: Sunday, February 21, 2016 3:14 AM
> To: Tomcat Users List 
> Subject: Re: Tomcat memory
>
> This is rather a Java than a tomcat question:
>
> The JVM allocates memory based on whatever default your current JVM 
> version decides (you don't mention what version of Java you're on)
>
> From a text on
> http://docs.oracle.com/javase/7/docs/technotes/guides/vm/gc-ergonomics
> .html
> that's linked from my Java's manpage:
>
> *initial heap size*
>
> Larger of 1/64th of the machine's physical memory on the machine
> or some reasonable minimum. Before J2SE 5.0, the default initial
> heap size was a reasonable minimum, which varies by platform.
> You can override this default using the |-Xms| command-line option.
>
> *maximum heap size*
>
> Smaller of 1/4th of the physical memory or 1GB. Before J2SE 5.0,
> the default maximum heap size was 64MB. You can override this
> default using the |-Xmx| command-line option.
>
> *Note:* The boundaries and fractions given for the heap size are
> correct for J2SE 5.0. They are likely to be different in subsequent
> releases as computers get more powerful.
>
> Note that this is from JavaSE7 and even mentions 5 - with more power there 
> comes more initial and maximum memory defaults.
>
> I'm not aware of the actual development of the default memory - mostly 
> because I consider it good practice to know what an application uses 
> and provide it explicitly, rather than relying on defaults. (and 
> frankly, on the applications that I see, the default typically is not 
> even enough - let alone a good basis for tuning)
>
> While we're at it: For production systems I consider it good practice to set 
> -Xms and -Xmx to the same value. Reason: If you don't have enough memory 
> available, you want to know this when the process starts, not days later when 
> it tries to allocate "the rest" - typically sunday night at 3am.
>
> Olaf
>
> Am 21.02.2016 um 03:39 schrieb Gokul.Baskaran:
>> Hi,
>>
>> I am currently running tomcat 7 in Windows 2012.
>>
>> The current JVM Heap memory parameters are set to empty, does the JVM Heap 
>> memory utilize the entire memory of the OS or does it default to a specific 
>> memory number?
>>
>> Thank you
>> -Gokul
>>
>>
>
> -
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RE: Tomcat memory

[Gokul . Baskaran]

Question was for Java 7

It is a Tomcat / Application question as well, as memory default can be 
configured in the application config. 

I totally agree that the best practice is to set the Xms and -Xmx. As am going 
to change the config, I would curious to know if the tomcat ui or the catalina 
does not have a Xms and -Xmx, would it default to 400MB? I read this in another 
forum. 

-Gokul


-Original Message-
From: Olaf Kock [mailto:tom...@olafkock.de] 
Sent: Sunday, February 21, 2016 3:14 AM
To: Tomcat Users List 
Subject: Re: Tomcat memory

This is rather a Java than a tomcat question:

The JVM allocates memory based on whatever default your current JVM version 
decides (you don't mention what version of Java you're on)

>From a text on
http://docs.oracle.com/javase/7/docs/technotes/guides/vm/gc-ergonomics.html
that's linked from my Java's manpage:

*initial heap size*

Larger of 1/64th of the machine's physical memory on the machine
or some reasonable minimum. Before J2SE 5.0, the default initial
heap size was a reasonable minimum, which varies by platform.
You can override this default using the |-Xms| command-line option.

*maximum heap size*

Smaller of 1/4th of the physical memory or 1GB. Before J2SE 5.0,
the default maximum heap size was 64MB. You can override this
default using the |-Xmx| command-line option.

*Note:* The boundaries and fractions given for the heap size are
correct for J2SE 5.0. They are likely to be different in subsequent
releases as computers get more powerful.

Note that this is from JavaSE7 and even mentions 5 - with more power there 
comes more initial and maximum memory defaults.

I'm not aware of the actual development of the default memory - mostly because 
I consider it good practice to know what an application uses and provide it 
explicitly, rather than relying on defaults. (and frankly, on the applications 
that I see, the default typically is not even enough - let alone a good basis 
for tuning)

While we're at it: For production systems I consider it good practice to set 
-Xms and -Xmx to the same value. Reason: If you don't have enough memory 
available, you want to know this when the process starts, not days later when 
it tries to allocate "the rest" - typically sunday night at 3am.

Olaf

Am 21.02.2016 um 03:39 schrieb Gokul.Baskaran:
> Hi,
>
> I am currently running tomcat 7 in Windows 2012.
>
> The current JVM Heap memory parameters are set to empty, does the JVM Heap 
> memory utilize the entire memory of the OS or does it default to a specific 
> memory number?
>
> Thank you
> -Gokul
>
>


-
To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org
For additional commands, e-mail: users-h...@tomcat.apache.org

Tomcat memory

[Gokul . Baskaran]

Hi,

I am currently running tomcat 7 in Windows 2012.

The current JVM Heap memory parameters are set to empty, does the JVM Heap 
memory utilize the entire memory of the OS or does it default to a specific 
memory number?

Thank you
-Gokul