Thread: Out of memory

On Thu, Mar 24, 2011 at 9:23 PM, Jeremy Palmer <JPalmer@linz.govt.nz> wrote:
> I’ve been getting database out of memory failures with some queries which
> deal with a reasonable amount of data.
>
> I was wondering what I should be looking at to stop this from happening.
>
> The typical messages I been getting are like this:
> http://pastebin.com/Jxfu3nYm
> The OS is:
>
> Linux TSTLHAPP01 2.6.32-29-server #58-Ubuntu SMP Fri Feb 11 21:06:51 UTC
> 2011 x86_64 GNU/Linux.
>
> It’s a running on VMWare and, has 2 CPU’s and 8GB of RAM. This VM is
> dedicated to PostgreSQL. The main OS parameters I have tuned are:
>
> work_mem = 200MB

That's a really big work_mem.  I have mainline db servers with 128G of
ram that have work_mem set to 16M and that is still considered a
little high in my book.  If you drop work_mem down to 1MB does the out
of memory go away?  work_mem is how much memory EACH sort can use on
its own, if you have a plpgsql procedure that keeps running query
after query, it could use a LOT of memory really fast.

Hi Scott,

It was the work_mem that was set too high. I reduced it to 32mb and the function executed.

Just so I understand this. Every time a sort is performed within a function, the sort memory is allocated, and then it
notreleased until the function completes? Rather then deallocating the memory after each sort operation has completed. 

Thanks,
Jeremy

________________________________________
From: Scott Marlowe [scott.marlowe@gmail.com]
Sent: Friday, 25 March 2011 5:04 p.m.
To: Jeremy Palmer
Cc: pgsql-general@postgresql.org
Subject: Re: [GENERAL] Out of memory

On Thu, Mar 24, 2011 at 9:23 PM, Jeremy Palmer <JPalmer@linz.govt.nz> wrote:
> I’ve been getting database out of memory failures with some queries which
> deal with a reasonable amount of data.
>
> I was wondering what I should be looking at to stop this from happening.
>
> The typical messages I been getting are like this:
> http://pastebin.com/Jxfu3nYm
> The OS is:
>
> Linux TSTLHAPP01 2.6.32-29-server #58-Ubuntu SMP Fri Feb 11 21:06:51 UTC
> 2011 x86_64 GNU/Linux.
>
> It’s a running on VMWare and, has 2 CPU’s and 8GB of RAM. This VM is
> dedicated to PostgreSQL. The main OS parameters I have tuned are:
>
> work_mem = 200MB

That's a really big work_mem.  I have mainline db servers with 128G of
ram that have work_mem set to 16M and that is still considered a
little high in my book.  If you drop work_mem down to 1MB does the out
of memory go away?  work_mem is how much memory EACH sort can use on
its own, if you have a plpgsql procedure that keeps running query
after query, it could use a LOT of memory really fast.
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Thank you.
______________________________________________________________________________________________________

Hi. Your idea is cool - i think this feature ought to be added to
TODO. Sorted rows should be materialized when memory is exhaused, and
memory reused.

2011/3/26, Jeremy Palmer <JPalmer@linz.govt.nz>:
> Hi Scott,
>
> It was the work_mem that was set too high. I reduced it to 32mb and the
> function executed.
>
> Just so I understand this. Every time a sort is performed within a function,
> the sort memory is allocated, and then it not released until the function
> completes? Rather then deallocating the memory after each sort operation has
> completed.
>
> Thanks,
> Jeremy
>
> ________________________________________
> From: Scott Marlowe [scott.marlowe@gmail.com]
> Sent: Friday, 25 March 2011 5:04 p.m.
> To: Jeremy Palmer
> Cc: pgsql-general@postgresql.org
> Subject: Re: [GENERAL] Out of memory
>
> On Thu, Mar 24, 2011 at 9:23 PM, Jeremy Palmer <JPalmer@linz.govt.nz> wrote:
>> I’ve been getting database out of memory failures with some queries which
>> deal with a reasonable amount of data.
>>
>> I was wondering what I should be looking at to stop this from happening.
>>
>> The typical messages I been getting are like this:
>> http://pastebin.com/Jxfu3nYm
>> The OS is:
>>
>> Linux TSTLHAPP01 2.6.32-29-server #58-Ubuntu SMP Fri Feb 11 21:06:51 UTC
>> 2011 x86_64 GNU/Linux.
>>
>> It’s a running on VMWare and, has 2 CPU’s and 8GB of RAM. This VM is
>> dedicated to PostgreSQL. The main OS parameters I have tuned are:
>>
>> work_mem = 200MB
>
> That's a really big work_mem.  I have mainline db servers with 128G of
> ram that have work_mem set to 16M and that is still considered a
> little high in my book.  If you drop work_mem down to 1MB does the out
> of memory go away?  work_mem is how much memory EACH sort can use on
> its own, if you have a plpgsql procedure that keeps running query
> after query, it could use a LOT of memory really fast.
> ______________________________________________________________________________________________________
>
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> Thank you.
> ______________________________________________________________________________________________________
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--
------------
pasman

I'm wondering if there is a way to estimate the total amount of work memory that will be used for a single query (or
morespecifically a plpgsql function that runs a series of queries)  

The database that I'm setting up is a data warehouse which typically only has one query running at any given time.

Thanks,
Jeremy

-----Original Message-----
From: Jeremy Palmer
Sent: Saturday, 26 March 2011 9:57 p.m.
To: Scott Marlowe
Cc: pgsql-general@postgresql.org
Subject: RE: [GENERAL] Out of memory

Hi Scott,

It was the work_mem that was set too high. I reduced it to 32mb and the function executed.

Just so I understand this. Every time a sort is performed within a function, the sort memory is allocated, and then it
notreleased until the function completes? Rather then deallocating the memory after each sort operation has completed. 

Thanks,
Jeremy

________________________________________
From: Scott Marlowe [scott.marlowe@gmail.com]
Sent: Friday, 25 March 2011 5:04 p.m.
To: Jeremy Palmer
Cc: pgsql-general@postgresql.org
Subject: Re: [GENERAL] Out of memory

On Thu, Mar 24, 2011 at 9:23 PM, Jeremy Palmer <JPalmer@linz.govt.nz> wrote:
> I've been getting database out of memory failures with some queries which
> deal with a reasonable amount of data.
>
> I was wondering what I should be looking at to stop this from happening.
>
> The typical messages I been getting are like this:
> http://pastebin.com/Jxfu3nYm
> The OS is:
>
> Linux TSTLHAPP01 2.6.32-29-server #58-Ubuntu SMP Fri Feb 11 21:06:51 UTC
> 2011 x86_64 GNU/Linux.
>
> It's a running on VMWare and, has 2 CPU's and 8GB of RAM. This VM is
> dedicated to PostgreSQL. The main OS parameters I have tuned are:
>
> work_mem = 200MB

That's a really big work_mem.  I have mainline db servers with 128G of
ram that have work_mem set to 16M and that is still considered a
little high in my book.  If you drop work_mem down to 1MB does the out
of memory go away?  work_mem is how much memory EACH sort can use on
its own, if you have a plpgsql procedure that keeps running query
after query, it could use a LOT of memory really fast.
______________________________________________________________________________________________________

This message contains information, which is confidential and may be subject to legal privilege.
If you are not the intended recipient, you must not peruse, use, disseminate, distribute or copy this message.
If you have received this message in error, please notify us immediately (Phone 0800 665 463 or info@linz.govt.nz) and
destroythe original message. 
LINZ accepts no responsibility for changes to this email, or for any attachments, after its transmission from LINZ.

Thank you.
______________________________________________________________________________________________________