IIS Memory leak

I wasn't claiming that we have a memory leak. I said we
were trying to determine IF we had one. This is a large
site 10,000+ asp pages, connecting to an SQL Server 2000
database server.

My real question was what behavior do people see with a
memory leak. Does memory NEVER get returned, or does it
go up and down a little, with the overall trend
continually increasing? In the 6 hours since I started
the logging, that was the trend I was seeing. Going up a
certain amount, then coming down, but not back to where
it was. So it would go up some, come down a little, go
up some more, come down a little, etc. I had only been
watching it for 6 hours when I posted that question.

I will continue logging for a few days to see what
happens.

We have 3 IIS5 servers in a cluster using a Cisco Content
Switch. Two of the servers have 1GB of RAM, and the
thrid has 2GB or RAM. The website is running in Isloated
mode on all three servers. On the two with 1GB of RAM,
when the server get's down to about 200MB free (which
takes about a week), IIS starts throwing the general 500
Internal Server Error. On the server with 2GB of RAM,
this happens after the server get's down to about 950MB
free.

On all 3 servers, free RAM just slowly drops over the
course of a week or 2.

Pete

 >-----Original Message-----
 >You have to be very careful in distinguishing memory
leaks and "aggressive
 >caching".
 >- Memory leak is memory that is allocated, possibly
used, and then "lost
 >track of".
 >- "Aggressive caching" is memory that is allocated and
being used, but it is
 >not lost and will be eventually freed. For example,
telling IIS to use up
 >to 400MB of RAM as a file cache
 >
 >
 >Personally, looking at a 6 hour trend and it moves
between 375MB and 410MB,
 >I am not concerned. I don't know if after 12 hours your
memory usage hovers
 >around 400MB or 600MB. If you come back after 24 hours
and it's at 800MB
 >and after 48 hours it is 1.6GB and the website(s)
involved is pretty
 >"small", then I would think memory leak. Until you have
a "profile" of
 >memory use by your app, you really can't say "memory
leak". For example,
 >your app's configuration may be using 1GB of memory
in "steady state", so
 >watching RAM increase until 1GB is no concern.
 >
 >It is not clear whether you are claiming a memory leak
in IIS itself or a
 >memory leak in 3rd party code run on IIS, including your
own.
 >
 >--
 >//David
 >IIS
 >This posting is provided "AS IS" with no warranties, and
confers no rights.
 >//
 >"Peter Conlan" <anonymous.DeleteThis@discussions.microsoft.com>
wrote in message
 >news:c09601c40877$ecfcfdf0$a501280a@phx.gbl...
 >We are currently trying to determine if we have a memory
 >leak. I have searched and seen a number of posts about
 >looking at Process\Private Bytes and Process\Virtual
 >Bytes.
 >
 >What I have read indicates that if Private Bytes is
 >increasing, you have a memory leak. In our case Private
 >Bytes seems to go up and down over short periods, but the
 >overall trend is up. When I started logging, it was at
 >375MB, and about 6 hours later it is at about 410MB.
 >
 >Is this the kind of thing that would be seen in a memory
 >leak, or would it be a situation where Private Bytes
 >NEVER went down?
 >
 >Virtual Bytes is very flat. It was at 1GB and then all
 >of a sudden jumped to 1.2 GB and stayed there.
 >
 >Also, I recently ran across a post by Pat Filoteo that
 >listed some practices that are poor memory performers or
 >cause memory fragmentation. Listed were: concatenation,
 >the use of ReDim in a loop. Are there any others?
 >
 >He also mentioned that each concatenation hits memory 6
 >times. Could we get some more details on that?
 >
 >Any information would be appreciated.
 >
 >Thanks,
 >Pete Conlan
 >
 >
 >.
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: IIS Memory leak 

A "Memory Leak" is characterized by code allocating memory but will never
deallocate. that memory until the process dies. Note that this can look
strikingly similar to the "Aggressive Caching" that I mentioned earlier,
where code intentionally allocates memory for a stated purpose (may be in
direct conjunction with a feature) and may deallocate that memory upon
server shutdown as the process dies.

Memory leak can manifest itself as a "wave" or "sawtooth" that trends
upwards, or as a line trending upwards. Think about it this way -- if code
allocated 50KB, waiting a while, then freed 49KB, waited a while, and then
allocated 50KB again... that's leaking 1KB memory with each iteration even
if the memory usage goes up and down.

Your situation sounds like there is heap fragmentation (2GB machine dying
with around 1GB RAM free).

--
//David
IIS
This posting is provided "AS IS" with no warranties, and confers no rights.
//
<anonymous.RemoveThis@discussions.microsoft.com> wrote in message
news:d5fe01c40ab6$9e1aab10$a501280a@phx.gbl...
I wasn't claiming that we have a memory leak. I said we
were trying to determine IF we had one. This is a large
site 10,000+ asp pages, connecting to an SQL Server 2000
database server.

My real question was what behavior do people see with a
memory leak. Does memory NEVER get returned, or does it
go up and down a little, with the overall trend
continually increasing? In the 6 hours since I started
the logging, that was the trend I was seeing. Going up a
certain amount, then coming down, but not back to where
it was. So it would go up some, come down a little, go
up some more, come down a little, etc. I had only been
watching it for 6 hours when I posted that question.

I will continue logging for a few days to see what
happens.

We have 3 IIS5 servers in a cluster using a Cisco Content
Switch. Two of the servers have 1GB of RAM, and the
thrid has 2GB or RAM. The website is running in Isloated
mode on all three servers. On the two with 1GB of RAM,
when the server get's down to about 200MB free (which
takes about a week), IIS starts throwing the general 500
Internal Server Error. On the server with 2GB of RAM,
this happens after the server get's down to about 950MB
free.

On all 3 servers, free RAM just slowly drops over the
course of a week or 2.

Pete

 >-----Original Message-----
 >You have to be very careful in distinguishing memory
leaks and "aggressive
 >caching".
 >- Memory leak is memory that is allocated, possibly
used, and then "lost
 >track of".
 >- "Aggressive caching" is memory that is allocated and
being used, but it is
 >not lost and will be eventually freed. For example,
telling IIS to use up
 >to 400MB of RAM as a file cache
 >
 >
 >Personally, looking at a 6 hour trend and it moves
between 375MB and 410MB,
 >I am not concerned. I don't know if after 12 hours your
memory usage hovers
 >around 400MB or 600MB. If you come back after 24 hours
and it's at 800MB
 >and after 48 hours it is 1.6GB and the website(s)
involved is pretty
 >"small", then I would think memory leak. Until you have
a "profile" of
 >memory use by your app, you really can't say "memory
leak". For example,
 >your app's configuration may be using 1GB of memory
in "steady state", so
 >watching RAM increase until 1GB is no concern.
 >
 >It is not clear whether you are claiming a memory leak
in IIS itself or a
 >memory leak in 3rd party code run on IIS, including your
own.
 >
 >--
 >//David
 >IIS
 >This posting is provided "AS IS" with no warranties, and
confers no rights.
 >//
 >"Peter Conlan" <anonymous.RemoveThis@discussions.microsoft.com>
wrote in message
 >news:c09601c40877$ecfcfdf0$a501280a@phx.gbl...
 >We are currently trying to determine if we have a memory
 >leak. I have searched and seen a number of posts about
 >looking at Process\Private Bytes and Process\Virtual
 >Bytes.
 >
 >What I have read indicates that if Private Bytes is
 >increasing, you have a memory leak. In our case Private
 >Bytes seems to go up and down over short periods, but the
 >overall trend is up. When I started logging, it was at
 >375MB, and about 6 hours later it is at about 410MB.
 >
 >Is this the kind of thing that would be seen in a memory
 >leak, or would it be a situation where Private Bytes
 >NEVER went down?
 >
 >Virtual Bytes is very flat. It was at 1GB and then all
 >of a sudden jumped to 1.2 GB and stayed there.
 >
 >Also, I recently ran across a post by Pat Filoteo that
 >listed some practices that are poor memory performers or
 >cause memory fragmentation. Listed were: concatenation,
 >the use of ReDim in a loop. Are there any others?
 >
 >He also mentioned that each concatenation hits memory 6
 >times. Could we get some more details on that?
 >
 >Any information would be appreciated.
 >
 >Thanks,
 >Pete Conlan
 >
 >
 >.
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: IIS Memory leak 

Thanks David.

I was wondering about fragmentation also. The post by
Pat Filoteo I mentioned in my first post also talked a
little about that. I do know that our developers do a
lot of string concatenation, and I need to check on thier
use of redim. Are there any other big things that can
cause heap fragmentation?

Thanks for your help,

Pete

 >-----Original Message-----
 >A "Memory Leak" is characterized by code allocating
memory but will never
 >deallocate. that memory until the process dies. Note
that this can look
 >strikingly similar to the "Aggressive Caching" that I
mentioned earlier,
 >where code intentionally allocates memory for a stated
purpose (may be in
 >direct conjunction with a feature) and may deallocate
that memory upon
 >server shutdown as the process dies.
 >
 >Memory leak can manifest itself as a "wave"
or "sawtooth" that trends
 >upwards, or as a line trending upwards. Think about it
this way -- if code
 >allocated 50KB, waiting a while, then freed 49KB, waited
a while, and then
 >allocated 50KB again... that's leaking 1KB memory with
each iteration even
 >if the memory usage goes up and down.
 >
 >Your situation sounds like there is heap fragmentation
(2GB machine dying
 >with around 1GB RAM free).
 >
 >--
 >//David
 >IIS
 >This posting is provided "AS IS" with no warranties, and
confers no rights.
 >//
 ><anonymous.DeleteThis@discussions.microsoft.com> wrote in message
 >news:d5fe01c40ab6$9e1aab10$a501280a@phx.gbl...
 >I wasn't claiming that we have a memory leak. I said we
 >were trying to determine IF we had one. This is a large
 >site 10,000+ asp pages, connecting to an SQL Server 2000
 >database server.
 >
 >My real question was what behavior do people see with a
 >memory leak. Does memory NEVER get returned, or does it
 >go up and down a little, with the overall trend
 >continually increasing? In the 6 hours since I started
 >the logging, that was the trend I was seeing. Going up a
 >certain amount, then coming down, but not back to where
 >it was. So it would go up some, come down a little, go
 >up some more, come down a little, etc. I had only been
 >watching it for 6 hours when I posted that question.
 >
 >I will continue logging for a few days to see what
 >happens.
 >
 >We have 3 IIS5 servers in a cluster using a Cisco Content
 >Switch. Two of the servers have 1GB of RAM, and the
 >thrid has 2GB or RAM. The website is running in Isloated
 >mode on all three servers. On the two with 1GB of RAM,
 >when the server get's down to about 200MB free (which
 >takes about a week), IIS starts throwing the general 500
 >Internal Server Error. On the server with 2GB of RAM,
 >this happens after the server get's down to about 950MB
 >free.
 >
 >On all 3 servers, free RAM just slowly drops over the
 >course of a week or 2.
 >
 >Pete
 >
  >>-----Original Message-----
  >>You have to be very careful in distinguishing memory
 >leaks and "aggressive
  >>caching".
  >>- Memory leak is memory that is allocated, possibly
 >used, and then "lost
  >>track of".
  >>- "Aggressive caching" is memory that is allocated and
 >being used, but it is
  >>not lost and will be eventually freed. For example,
 >telling IIS to use up
  >>to 400MB of RAM as a file cache
  >>
  >>
  >>Personally, looking at a 6 hour trend and it moves
 >between 375MB and 410MB,
  >>I am not concerned. I don't know if after 12 hours your
 >memory usage hovers
  >>around 400MB or 600MB. If you come back after 24 hours
 >and it's at 800MB
  >>and after 48 hours it is 1.6GB and the website(s)
 >involved is pretty
  >>"small", then I would think memory leak. Until you have
 >a "profile" of
  >>memory use by your app, you really can't say "memory
 >leak". For example,
  >>your app's configuration may be using 1GB of memory
 >in "steady state", so
  >>watching RAM increase until 1GB is no concern.
  >>
  >>It is not clear whether you are claiming a memory leak
 >in IIS itself or a
  >>memory leak in 3rd party code run on IIS, including your
 >own.
  >>
  >>--
  >>//David
  >>IIS
  >>This posting is provided "AS IS" with no warranties, and
 >confers no rights.
  >>//
  >>"Peter Conlan" <anonymous.DeleteThis@discussions.microsoft.com>
 >wrote in message
  >>news:c09601c40877$ecfcfdf0$a501280a@phx.gbl...
  >>We are currently trying to determine if we have a memory
  >>leak. I have searched and seen a number of posts about
  >>looking at Process\Private Bytes and Process\Virtual
  >>Bytes.
  >>
  >>What I have read indicates that if Private Bytes is
  >>increasing, you have a memory leak. In our case Private
  >>Bytes seems to go up and down over short periods, but
the
  >>overall trend is up. When I started logging, it was at
  >>375MB, and about 6 hours later it is at about 410MB.
  >>
  >>Is this the kind of thing that would be seen in a memory
  >>leak, or would it be a situation where Private Bytes
  >>NEVER went down?
  >>
  >>Virtual Bytes is very flat. It was at 1GB and then all
  >>of a sudden jumped to 1.2 GB and stayed there.
  >>
  >>Also, I recently ran across a post by Pat Filoteo that
  >>listed some practices that are poor memory performers or
  >>cause memory fragmentation. Listed were: concatenation,
  >>the use of ReDim in a loop. Are there any others?
  >>
  >>He also mentioned that each concatenation hits memory 6
  >>times. Could we get some more details on that?
  >>
  >>Any information would be appreciated.
  >>
  >>Thanks,
  >>Pete Conlan
  >>
  >>
  >>.
  >>
 >
 >
 >.
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: IIS Memory leak 

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"Peter Conlan" <anonymous.DeleteThis@discussions.microsoft.com> wrote in message
news:c09601c40877$ecfcfdf0$a501280a@phx.gbl...
 > We are currently trying to determine if we have a memory
 > leak. I have searched and seen a number of posts about
 > looking at Process\Private Bytes and Process\Virtual
 > Bytes.
 >
 > What I have read indicates that if Private Bytes is
 > increasing, you have a memory leak. In our case Private
 > Bytes seems to go up and down over short periods, but the
 > overall trend is up. When I started logging, it was at
 > 375MB, and about 6 hours later it is at about 410MB.
 >
 > Is this the kind of thing that would be seen in a memory
 > leak, or would it be a situation where Private Bytes
 > NEVER went down?
 >
 > Virtual Bytes is very flat. It was at 1GB and then all
 > of a sudden jumped to 1.2 GB and stayed there.
 >
 > Also, I recently ran across a post by Pat Filoteo that
 > listed some practices that are poor memory performers or
 > cause memory fragmentation. Listed were: concatenation,
 > the use of ReDim in a loop. Are there any others?
 >
 > He also mentioned that each concatenation hits memory 6
 > times. Could we get some more details on that?
 >
 > Any information would be appreciated.
 >
 > Thanks,
 > Pete Conlan
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: IIS Memory leak