I've noticed that Powershell likes to eat LOTS of memory. I think it has to
do with .net and garbage collection. I've done a test with wmi and then
removing the variable. It seems that memory will continually increase
without ever going to a stable level. I thought it would increase until
garbage collection runs, but it never seems to stabilize. My thought is
that the heap gets fragmented and therefore can't release all of the freed
memory.

I've found something that seems to have stabilized it, but I think there may
be some drawbacks. I've added "[GC]::Collect()" to my prompt function to
force garbage collection. Does anyone know what type of issues I may see
from this? Or, is there another way to make it free up the memory more
efficiently?



Test Case 1: Keeps using memory.
$a = get-wmiobject Win32_NTLogEvent ; remove-variable a;
[math]::floor((get-process powershell).PrivateMemorySize/1MB)

Test Case 2: Memory stabilizes after a few executions (3-4).
[GC]::Collect() has been added.
$a = gwmi Win32_NTLogEvent ; remove-variable a; [GC]::Collect();
[math]::floor((get-process powershell).PrivateMemorySize/1MB)

Thanks,

SQL Guru

What you are seeing is just that the Garbage collector doesn't run unless it
has to (memory pressure). There's quite a few articles around explaining
how it works if youre interested. Anyway I don't think you'll see any
issues from the [GC]::Collect() in your prompt function (other than some
performance degradation from running the garbage collector all the time) but
you really shouldn't need it.

"SQL Guru" <myjunk_abcd at hotmail dot com> wrote in message
news:elBqkXpWHHA.496@TK2MSFTNGP06.phx.gbl...
> I've noticed that Powershell likes to eat LOTS of memory. I think it has
> to
> do with .net and garbage collection. I've done a test with wmi and then
> removing the variable. It seems that memory will continually increase
> without ever going to a stable level. I thought it would increase until
> garbage collection runs, but it never seems to stabilize. My thought is
> that the heap gets fragmented and therefore can't release all of the freed
> memory.
>
> I've found something that seems to have stabilized it, but I think there
> may
> be some drawbacks. I've added "[GC]::Collect()" to my prompt function to
> force garbage collection. Does anyone know what type of issues I may see
> from this? Or, is there another way to make it free up the memory more
> efficiently?
>
> Test Case 1: Keeps using memory.
> $a = get-wmiobject Win32_NTLogEvent ; remove-variable a;
> [math]::floor((get-process powershell).PrivateMemorySize/1MB)
>
> Test Case 2: Memory stabilizes after a few executions (3-4).
> [GC]::Collect() has been added.
> $a = gwmi Win32_NTLogEvent ; remove-variable a; [GC]::Collect();
> [math]::floor((get-process powershell).PrivateMemorySize/1MB)
>
> Thanks,
>
> SQL Guru
>

That is exactly what happens.

To quote the original poster:

> I thought it would increase until
> garbage collection runs, but it never seems to stabilize.

And that happens. The GC just does not run. Why SHOULD it? The memory is not
needed :-) GC costs time.

Thomas

"Marcel J. Ortiz [MSFT]" <mosoto@online.microsoft.com> wrote in message
news:7EC4F61A-B635-4233-B353-B626CF671E60@microsoft.com...
> What you are seeing is just that the Garbage collector doesn't run unless
> it has to (memory pressure). There's quite a few articles around
> explaining how it works if youre interested. Anyway I don't think you'll
> see any issues from the [GC]::Collect() in your prompt function (other
> than some performance degradation from running the garbage collector all
> the time) but you really shouldn't need it.
>
> "SQL Guru" <myjunk_abcd at hotmail dot com> wrote in message
> news:elBqkXpWHHA.496@TK2MSFTNGP06.phx.gbl...
>> I've noticed that Powershell likes to eat LOTS of memory. I think it has
>> to
>> do with .net and garbage collection. I've done a test with wmi and then
>> removing the variable. It seems that memory will continually increase
>> without ever going to a stable level. I thought it would increase until
>> garbage collection runs, but it never seems to stabilize. My thought is
>> that the heap gets fragmented and therefore can't release all of the
>> freed
>> memory.
>>
>> I've found something that seems to have stabilized it, but I think there
>> may
>> be some drawbacks. I've added "[GC]::Collect()" to my prompt function to
>> force garbage collection. Does anyone know what type of issues I may see
>> from this? Or, is there another way to make it free up the memory more
>> efficiently?
>>
>> Test Case 1: Keeps using memory.
>> $a = get-wmiobject Win32_NTLogEvent ; remove-variable a;
>> [math]::floor((get-process powershell).PrivateMemorySize/1MB)
>>
>> Test Case 2: Memory stabilizes after a few executions (3-4).
>> [GC]::Collect() has been added.
>> $a = gwmi Win32_NTLogEvent ; remove-variable a; [GC]::Collect();
>> [math]::floor((get-process powershell).PrivateMemorySize/1MB)
>>
>> Thanks,
>>
>> SQL Guru
>>
>

I have 1 GB of physical memory in my system. If I have 1.8 GB committed,
memory usage is growing, my system is dirt slow from swapping, and garbage
collection still isn't needed; then I have no clue what would trigger it on
its own. The cost of garbage collection is almost nothing compared to the
cost of it not freeing memory. I don't know why this happens, but it does
and I've seen it on other peoples systems as well. I understand the idea of
garbage collection not running immediately and I agree that it normally
shouldn't. I just believe it should be a little more consistent/aggressive
with freeing memory.

SQL_Guru

"Thomas Tomiczek" <t.tomiczek@nettecture.com> wrote in message
news:54108F9F-6AB0-4867-92AC-F9B3E33F5172@microsoft.com...
That is exactly what happens.

To quote the original poster:

> I thought it would increase until
> garbage collection runs, but it never seems to stabilize.

And that happens. The GC just does not run. Why SHOULD it? The memory is not
needed :-) GC costs time.

Thomas

"Marcel J. Ortiz [MSFT]" <mosoto@online.microsoft.com> wrote in message
news:7EC4F61A-B635-4233-B353-B626CF671E60@microsoft.com...
> What you are seeing is just that the Garbage collector doesn't run unless
> it has to (memory pressure). There's quite a few articles around
> explaining how it works if youre interested. Anyway I don't think you'll
> see any issues from the [GC]::Collect() in your prompt function (other
> than some performance degradation from running the garbage collector all
> the time) but you really shouldn't need it.
>
> "SQL Guru" <myjunk_abcd at hotmail dot com> wrote in message
> news:elBqkXpWHHA.496@TK2MSFTNGP06.phx.gbl...
>> I've noticed that Powershell likes to eat LOTS of memory. I think it has
>> to
>> do with .net and garbage collection. I've done a test with wmi and then
>> removing the variable. It seems that memory will continually increase
>> without ever going to a stable level. I thought it would increase until
>> garbage collection runs, but it never seems to stabilize. My thought is
>> that the heap gets fragmented and therefore can't release all of the
>> freed
>> memory.
>>
>> I've found something that seems to have stabilized it, but I think there
>> may
>> be some drawbacks. I've added "[GC]::Collect()" to my prompt function to
>> force garbage collection. Does anyone know what type of issues I may see
>> from this? Or, is there another way to make it free up the memory more
>> efficiently?
>>
>> Test Case 1: Keeps using memory.
>> $a = get-wmiobject Win32_NTLogEvent ; remove-variable a;
>> [math]::floor((get-process powershell).PrivateMemorySize/1MB)
>>
>> Test Case 2: Memory stabilizes after a few executions (3-4).
>> [GC]::Collect() has been added.
>> $a = gwmi Win32_NTLogEvent ; remove-variable a; [GC]::Collect();
>> [math]::floor((get-process powershell).PrivateMemorySize/1MB)
>>
>> Thanks,
>>
>> SQL Guru
>>
>

to do be so extreme you could have your prompt only call GC every X
number or times, or evey Y # of minutes

a situations when it is good to call the GC is if you are youiung a
com object , and you get rid of it, but you want to ensure it goes
away. I.e you make a com object of excel.. and that process is created
then you do $xl.quit
then you remove the variable so their is no reference count.. but
wrong.. there still is a reference count because the dotnet variable
is waiting for GC.. then to get rid of that excel process you should
call the garbage collection.