IIS Template Cache and Script Engine Cache

Ok, I went and asked the ASP Dev about it, so I will share what I've
understood. Hopefully, more explanations will be blogged by the dev sometime
soon. At a glance, what I'm going to say does not seem to match anything
that you've asked.

The two concepts you are asking about is the "Template Cache" and "Script
Engine Cache".

The "Template Cache" is a cache of the intermediate form of the particular
ASP page which has all necessary script code (including include files) and
other parsed info from the HTML portions of the ASP page. This template can
be directly interpreted by a Script Engine to produce the ASP page's output.
It is NOT a response cache (i.e. cache of script execution). Treat the
templates as an intermediate form of an ASP page that has not been
interpreted.

ASP has an option to either not use Templates (this is merely a perf issue
and does not affect functionality), cache all Templates in memory, or cache
a portion in memory and the rest on disk inside the configurable "ASP
Compiled Templates" directory.

The "Script Engine Cache" refers to a cache of the actual Script Engine
objects that are used to interpret scripts. These objects are expensive to
create/tear-down per ASP request (sort of like how Processes are expensive
to create/tear-down), so what ASP does is create a pool of Script Engine
objects (you get to control the number of such objects in the pool), and
everytime ASP needs to execute a template to produce output, it uses a free
Script Engine from the pool.


Thus, you can see that "Script Engine Cache" is a direct measure of "how
many scripts can be theoretically executed concurrently by ASP". This
measure of concurrent execution is further bounded by the max number of
worker threads feeding templates into the Script Engines, so it does not
make sense to have this value be very large nor very small (if very large,
you're just wasting memory/resources on Engines that barely get used; if
very small, you end up bottlenecking the concurrency of script execution
because you have more worker threads feeding in templates than there are
available Script Engines to execute them).

The "Template Cache" is basically storing all the necessary pre-processing
of an ASP page prior to actual generation of dynamic response by a Script
Engine from the "Script Engine Cache".

Neither of these caches are the "Response Cache" that you alluded to.

--
//David
IIS
This posting is provided "AS IS" with no warranties, and confers no rights.
//
"Peter Conlan" <anonymous.TakeThisOut@discussions.microsoft.com> wrote in message
news:10a9601c40ed3$19a04a40$a301280a@phx.gbl...
I have done some reading of various posts and websites
trying to get an understanding of theses caches. I have
some questions.

What I have read says that when an asp page is first
requested, a text copy (with all includes inserted into
the text) of it is stored in the Template Cache. This
text copy is the "Template". My questions are:

Does this template contain the HTML code also, or just
the script code?

Is it really just a copy of the entire asp page?

If I understand things so far, none of script has been
executed at this point. This is just a copy of the asp
page the server can use later (assuming it is still in
the cache) rather than going to disk to get it. Correct?

My understanding of the Script Engine Cache is that after
a page has been put into the template cache, the asp
script is interpreted and stored in the template cache.
If requested later, the server can use the previously
interpreted cache version rather than spending time
interpreting it again. My questions on this are:

Does the Script Engine Cache contain only script
associated with a templates in the template cache? In
other words, is it ONLY asp script and no HTML? If there
is no HTML, does it get the HTML from it's associated
Template?

Again, I am assuming that the cached Script Engines are
script that has not been executed, meaning the results of
of running the script are not in the cache. The cached
Script Engine could be executed multiple times with
different results depending on the values (from a
querystring, or record set, etc. ) supplied to it. Is
this correct?

I support a large asp site, so I am just trying to get a
better understanding of how things work.

Thanks,

Pete Conlan
 >> Stay informed about: IIS Template Cache and Script Engine Cache 

Thanks David, that is great information.

The only thing I am not 100% clear on is the part about
the templates in the template cache containing "other
parsed info from the HTML portions of the ASP page".

By this do you mean that the HTML that is in the asp page
is in the template also, or only certain items? Given
that you said the Script Engines can directly interpret
the template to produce the output, it would seem like
the template would contain the HTML from the asp page as
well. I just want to be sure I understand correctly.

Thanks again.

Pete

 >-----Original Message-----
 >Ok, I went and asked the ASP Dev about it, so I will
share what I've
 >understood. Hopefully, more explanations will be blogged
by the dev sometime
 >soon. At a glance, what I'm going to say does not seem
to match anything
 >that you've asked.
 >
 >The two concepts you are asking about is the "Template
Cache" and "Script
 >Engine Cache".
 >
 >The "Template Cache" is a cache of the intermediate form
of the particular
 >ASP page which has all necessary script code (including
include files) and
 >other parsed info from the HTML portions of the ASP
page. This template can
 >be directly interpreted by a Script Engine to produce
the ASP page's output.
 >It is NOT a response cache (i.e. cache of script
execution). Treat the
 >templates as an intermediate form of an ASP page that
has not been
 >interpreted.
 >
 >ASP has an option to either not use Templates (this is
merely a perf issue
 >and does not affect functionality), cache all Templates
in memory, or cache
 >a portion in memory and the rest on disk inside the
configurable "ASP
 >Compiled Templates" directory.
 >
 >The "Script Engine Cache" refers to a cache of the
actual Script Engine
 >objects that are used to interpret scripts. These
objects are expensive to
 >create/tear-down per ASP request (sort of like how
Processes are expensive
 >to create/tear-down), so what ASP does is create a pool
of Script Engine
 >objects (you get to control the number of such objects
in the pool), and
 >everytime ASP needs to execute a template to produce
output, it uses a free
 >Script Engine from the pool.
 >
 >
 >Thus, you can see that "Script Engine Cache" is a direct
measure of "how
 >many scripts can be theoretically executed concurrently
by ASP". This
 >measure of concurrent execution is further bounded by
the max number of
 >worker threads feeding templates into the Script
Engines, so it does not
 >make sense to have this value be very large nor very
small (if very large,
 >you're just wasting memory/resources on Engines that
barely get used; if
 >very small, you end up bottlenecking the concurrency of
script execution
 >because you have more worker threads feeding in
templates than there are
 >available Script Engines to execute them).
 >
 >The "Template Cache" is basically storing all the
necessary pre-processing
 >of an ASP page prior to actual generation of dynamic
response by a Script
 >Engine from the "Script Engine Cache".
 >
 >Neither of these caches are the "Response Cache" that
you alluded to.
 >
 >--
 >//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:10a9601c40ed3$19a04a40$a301280a@phx.gbl...
 >I have done some reading of various posts and websites
 >trying to get an understanding of theses caches. I have
 >some questions.
 >
 >What I have read says that when an asp page is first
 >requested, a text copy (with all includes inserted into
 >the text) of it is stored in the Template Cache. This
 >text copy is the "Template". My questions are:
 >
 >Does this template contain the HTML code also, or just
 >the script code?
 >
 >Is it really just a copy of the entire asp page?
 >
 >If I understand things so far, none of script has been
 >executed at this point. This is just a copy of the asp
 >page the server can use later (assuming it is still in
 >the cache) rather than going to disk to get it. Correct?
 >
 >My understanding of the Script Engine Cache is that after
 >a page has been put into the template cache, the asp
 >script is interpreted and stored in the template cache.
 >If requested later, the server can use the previously
 >interpreted cache version rather than spending time
 >interpreting it again. My questions on this are:
 >
 >Does the Script Engine Cache contain only script
 >associated with a templates in the template cache? In
 >other words, is it ONLY asp script and no HTML? If there
 >is no HTML, does it get the HTML from it's associated
 >Template?
 >
 >Again, I am assuming that the cached Script Engines are
 >script that has not been executed, meaning the results of
 >of running the script are not in the cache. The cached
 >Script Engine could be executed multiple times with
 >different results depending on the values (from a
 >querystring, or record set, etc. ) supplied to it. Is
 >this correct?
 >
 >I support a large asp site, so I am just trying to get a
 >better understanding of how things work.
 >
 >Thanks,
 >
 >Pete Conlan
 >
 >
 >.
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: IIS Template Cache and Script Engine Cache 

David,

I do have one more question:

If an asp page is using vbscript and server-side jscript,
will it use 2 script engines? Or will one script engine
hande both vbscript and jscript?

Thanks,

Pete

 >-----Original Message-----
 >Ok, I went and asked the ASP Dev about it, so I will
share what I've
 >understood. Hopefully, more explanations will be blogged
by the dev sometime
 >soon. At a glance, what I'm going to say does not seem
to match anything
 >that you've asked.
 >
 >The two concepts you are asking about is the "Template
Cache" and "Script
 >Engine Cache".
 >
 >The "Template Cache" is a cache of the intermediate form
of the particular
 >ASP page which has all necessary script code (including
include files) and
 >other parsed info from the HTML portions of the ASP
page. This template can
 >be directly interpreted by a Script Engine to produce
the ASP page's output.
 >It is NOT a response cache (i.e. cache of script
execution). Treat the
 >templates as an intermediate form of an ASP page that
has not been
 >interpreted.
 >
 >ASP has an option to either not use Templates (this is
merely a perf issue
 >and does not affect functionality), cache all Templates
in memory, or cache
 >a portion in memory and the rest on disk inside the
configurable "ASP
 >Compiled Templates" directory.
 >
 >The "Script Engine Cache" refers to a cache of the
actual Script Engine
 >objects that are used to interpret scripts. These
objects are expensive to
 >create/tear-down per ASP request (sort of like how
Processes are expensive
 >to create/tear-down), so what ASP does is create a pool
of Script Engine
 >objects (you get to control the number of such objects
in the pool), and
 >everytime ASP needs to execute a template to produce
output, it uses a free
 >Script Engine from the pool.
 >
 >
 >Thus, you can see that "Script Engine Cache" is a direct
measure of "how
 >many scripts can be theoretically executed concurrently
by ASP". This
 >measure of concurrent execution is further bounded by
the max number of
 >worker threads feeding templates into the Script
Engines, so it does not
 >make sense to have this value be very large nor very
small (if very large,
 >you're just wasting memory/resources on Engines that
barely get used; if
 >very small, you end up bottlenecking the concurrency of
script execution
 >because you have more worker threads feeding in
templates than there are
 >available Script Engines to execute them).
 >
 >The "Template Cache" is basically storing all the
necessary pre-processing
 >of an ASP page prior to actual generation of dynamic
response by a Script
 >Engine from the "Script Engine Cache".
 >
 >Neither of these caches are the "Response Cache" that
you alluded to.
 >
 >--
 >//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:10a9601c40ed3$19a04a40$a301280a@phx.gbl...
 >I have done some reading of various posts and websites
 >trying to get an understanding of theses caches. I have
 >some questions.
 >
 >What I have read says that when an asp page is first
 >requested, a text copy (with all includes inserted into
 >the text) of it is stored in the Template Cache. This
 >text copy is the "Template". My questions are:
 >
 >Does this template contain the HTML code also, or just
 >the script code?
 >
 >Is it really just a copy of the entire asp page?
 >
 >If I understand things so far, none of script has been
 >executed at this point. This is just a copy of the asp
 >page the server can use later (assuming it is still in
 >the cache) rather than going to disk to get it. Correct?
 >
 >My understanding of the Script Engine Cache is that after
 >a page has been put into the template cache, the asp
 >script is interpreted and stored in the template cache.
 >If requested later, the server can use the previously
 >interpreted cache version rather than spending time
 >interpreting it again. My questions on this are:
 >
 >Does the Script Engine Cache contain only script
 >associated with a templates in the template cache? In
 >other words, is it ONLY asp script and no HTML? If there
 >is no HTML, does it get the HTML from it's associated
 >Template?
 >
 >Again, I am assuming that the cached Script Engines are
 >script that has not been executed, meaning the results of
 >of running the script are not in the cache. The cached
 >Script Engine could be executed multiple times with
 >different results depending on the values (from a
 >querystring, or record set, etc. ) supplied to it. Is
 >this correct?
 >
 >I support a large asp site, so I am just trying to get a
 >better understanding of how things work.
 >
 >Thanks,
 >
 >Pete Conlan
 >
 >
 >.
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: IIS Template Cache and Script Engine Cache