Massive speed difference between identical asp pages

Discussion in 'ASP General' started by MikeT, Nov 17, 2004.

  1. MikeT

    MikeT Guest

    I have a page that produces little thumbnails of the 3D models it
    finds in a specified directory (and iterates down through any sub
    directories).

    It basically scans each directory for 3D Studio Max files using the
    filesystemobject and writes an activeX component called iDrop for each
    file so it can be displayed on the page (and drag-dropped straight
    into Max). If it happens to find a similarly named XML file in the
    directory, it loads that and transforms the content with a pre-loaded
    XSL stylesheet to provide a summary of the model's size/face
    count/etc. This is just for context though, just in case it is
    relevant.

    In response to complaints that it was running really slowly (from 6 to
    13 seconds to scan a directory with 3 models in it), I made a copy of
    the page to add debug timers to, so I could see where it was taking
    all the time.

    This copy completes in between 0.3 and 0.6 seconds for the same
    directory.

    The code is identical. I can cut and paste the code from the slow file
    to the fast one (or vice versa) and it makes no difference to the
    execution speed of either file. They both execute using the IUSR_foo
    account on the webserver. They are both in the same directory. The
    directory they are reading from has read permission for "Everyone".

    What gives? How is this possible? What is IIS doing differently for
    the two pages? Surely IIS should recompile a page if its modified date
    changes, so how can it compile two different execution schemes for the
    same code?

    The fix for me is to use the new page and not the old one, but I
    really want to know what is going on here.

    Server is IIS5.0 on Windows 2000 Server
     
    MikeT, Nov 17, 2004
    #1
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  2. MikeT

    Patrice Guest

    Have you found where exactly the time difference is ?

    For now it looks like to me that you see fast running server side code under
    all circumstances. If yes , the delay experienced by users is IMO the time
    taken to download all the 3D models so that they can be viewed by the
    (multiple) ActiveX control(s) hosted in your HTML page...

    If yes, you could try to donwload only those models the user actually wants
    to use...

    Patrice

    --

    "MikeT" <9.co.uk> a écrit dans le message de
    news:...
    > I have a page that produces little thumbnails of the 3D models it
    > finds in a specified directory (and iterates down through any sub
    > directories).
    >
    > It basically scans each directory for 3D Studio Max files using the
    > filesystemobject and writes an activeX component called iDrop for each
    > file so it can be displayed on the page (and drag-dropped straight
    > into Max). If it happens to find a similarly named XML file in the
    > directory, it loads that and transforms the content with a pre-loaded
    > XSL stylesheet to provide a summary of the model's size/face
    > count/etc. This is just for context though, just in case it is
    > relevant.
    >
    > In response to complaints that it was running really slowly (from 6 to
    > 13 seconds to scan a directory with 3 models in it), I made a copy of
    > the page to add debug timers to, so I could see where it was taking
    > all the time.
    >
    > This copy completes in between 0.3 and 0.6 seconds for the same
    > directory.
    >
    > The code is identical. I can cut and paste the code from the slow file
    > to the fast one (or vice versa) and it makes no difference to the
    > execution speed of either file. They both execute using the IUSR_foo
    > account on the webserver. They are both in the same directory. The
    > directory they are reading from has read permission for "Everyone".
    >
    > What gives? How is this possible? What is IIS doing differently for
    > the two pages? Surely IIS should recompile a page if its modified date
    > changes, so how can it compile two different execution schemes for the
    > same code?
    >
    > The fix for me is to use the new page and not the old one, but I
    > really want to know what is going on here.
    >
    > Server is IIS5.0 on Windows 2000 Server
     
    Patrice, Nov 17, 2004
    #2
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  3. MikeT

    Mark Schupp Guest

    Rename the "slow" file, then make a copy of the "fast" file with the "slow"
    file name. Is it still slow?

    Are you calling both files exactly the same way (by a link, form post, etc)?
    If you are calling by a link or form post swap the links and see if the
    performance problem follows the link.

    --
    --Mark Schupp
    Head of Development
    Integrity eLearning
    www.ielearning.com

    "MikeT" <9.co.uk> wrote in message
    news:...
    >I have a page that produces little thumbnails of the 3D models it
    > finds in a specified directory (and iterates down through any sub
    > directories).
    >
    > It basically scans each directory for 3D Studio Max files using the
    > filesystemobject and writes an activeX component called iDrop for each
    > file so it can be displayed on the page (and drag-dropped straight
    > into Max). If it happens to find a similarly named XML file in the
    > directory, it loads that and transforms the content with a pre-loaded
    > XSL stylesheet to provide a summary of the model's size/face
    > count/etc. This is just for context though, just in case it is
    > relevant.
    >
    > In response to complaints that it was running really slowly (from 6 to
    > 13 seconds to scan a directory with 3 models in it), I made a copy of
    > the page to add debug timers to, so I could see where it was taking
    > all the time.
    >
    > This copy completes in between 0.3 and 0.6 seconds for the same
    > directory.
    >
    > The code is identical. I can cut and paste the code from the slow file
    > to the fast one (or vice versa) and it makes no difference to the
    > execution speed of either file. They both execute using the IUSR_foo
    > account on the webserver. They are both in the same directory. The
    > directory they are reading from has read permission for "Everyone".
    >
    > What gives? How is this possible? What is IIS doing differently for
    > the two pages? Surely IIS should recompile a page if its modified date
    > changes, so how can it compile two different execution schemes for the
    > same code?
    >
    > The fix for me is to use the new page and not the old one, but I
    > really want to know what is going on here.
    >
    > Server is IIS5.0 on Windows 2000 Server
     
    Mark Schupp, Nov 17, 2004
    #3
  4. MikeT

    MikeT Guest

    "Mark Schupp" <> wrote in message news:<>...
    >
    > "MikeT" <9.co.uk> wrote in message
    > news:...
    > >I have a page that produces little thumbnails of the 3D models it
    > > finds in a specified directory (and iterates down through any sub
    > > directories).
    > >
    > > It basically scans each directory for 3D Studio Max files using the
    > > filesystemobject and writes an activeX component called iDrop for each
    > > file so it can be displayed on the page (and drag-dropped straight
    > > into Max). If it happens to find a similarly named XML file in the
    > > directory, it loads that and transforms the content with a pre-loaded
    > > XSL stylesheet to provide a summary of the model's size/face
    > > count/etc. This is just for context though, just in case it is
    > > relevant.
    > >

    >
    > Rename the "slow" file, then make a copy of the "fast" file with the "slow"
    > file name. Is it still slow?
    >

    The file with the "slow" name becomes slow. The one that was slow
    becomes fast :) This kinda proves that it's something IIS is doing
    when executing the code. The same thing happens with a second page in
    the same directory that is used as a detailed view for a particular
    model. Again, making a new file with a new name speeds up the code,
    but the slowdown is associated with the filename and not the code
    itself.

    > Are you calling both files exactly the same way (by a link, form post, etc)?
    > If you are calling by a link or form post swap the links and see if the
    > performance problem follows the link.
    >


    I'm typing in a direct URL to the page with the same parameter (a
    directory
    path to scan) for each.

    Patrice wrote:

    > Have you found where exactly the time difference is ?
    >


    Inserting more timing checks makes it clear that one page is taking
    around 2 seconds to run through the files in a directory, the other
    <0.2 seconds. Specifically, it's taking a long time to get a file's
    name. The code makes repeated use of objFile.Name. Caching this name
    in a string (which I should have been doing anyway, doh) speeds up
    BOTH pages immensely, but the slow down factor for the files is still
    around 16 to 1. So it's the FileSystemObject that's got the problem.
    Why would getting a file name be so slow?

    >
    >
    > For now it looks like to me that you see fast running server side code
    > under all circumstances.
    >

    Nope - the timings are being done on the server side, the activeX
    loads
    the models clientside, so won't slow down the execution of the ASP.

    > If yes, you could try to donwload only those models the user actually
    > wants to use...


    Point taken, but this is a model library browser - they don't know
    what
    model they are looking for, they are browsing, say, 100 office chairs
    looking
    for the right one for the scheme they are modelling.


    Hmm. It looks like IIS has cached something to do with the page's
    name that
    isn't getting reset when the page is edited. I'll try restarting the
    IIS server, but if that fails I'm assuming the IIS metabase has got
    corrupted for the files that were in that directory, but it's beyond
    me what it might have cached that affects behaviour in this way.


    Here's the code for the loop that is being so slow:
    (splittime is my debug code that logs the elapsed time in milliseconds
    for each call, and writeGalleryModel just outputs the HTML based on
    the available files, fso is a global fileSystemObject)

    sub listmodelsunder(libraryroot, librarywebroot, subpath, preview)

    dim thisFolder, subFolder, file
    dim bestproxyfile
    dim proxyfile
    dim xmlfile
    dim maxfile
    dim vrmlfile

    dim filename

    set thisfolder = fso.GetFolder(libraryroot & subpath)
    proxyfile = ""
    xmlfile = ""
    maxfile = ""
    vrmlfile = ""

    splittime(libraryroot & subpath)
    for each file in thisFolder.Files

    filename = file.Name 'THIS IS THE CALL THAT TAKES 16 TIMES LONGER
    ON ONE PAGE
    splittime(filename & " start")
    select case fileextension(filename)
    case "jpg"
    if proxyfile = "" then proxyfile = filename

    if instr(1,filename,"best",1) > 0 then bestproxyfile =filename
    if instr(1,filename,preview,1) > 0 then proxyfile = filename

    case "max"
    if maxfile = "" then
    maxfile = filename
    else
    if filename = thisFolder.Name & ".max" then
    maxfile = filename
    end if
    end if

    case "xml"
    if instr(1,filename,"fileproperties",1) > 0 then xmlfile =
    filename

    case "wrl"
    if vrmlfile = "" and preview = "3d" then vrmlfile = filename

    end select

    splittime(filename & " end")
    next
    splittime("scan complete")
    if proxyfile = "" or preview = "3d" then proxyfile = bestproxyfile

    if maxfile<>"" then 'this directory is a model, list it
    writeGalleryModel library & subpath, librarywebroot & subpath,
    proxyfile, maxfile, xmlfile, vrmlfile
    modelcount = modelcount + 1
    else
    for each subFolder in thisFolder.subFolders
    listmodelsunder libraryroot, librarywebroot, subpath & "/" &
    subFolder.Name, preview
    next
    end if

    set thisfolder = nothing
    end sub
     
    MikeT, Nov 18, 2004
    #4
  5. > the two pages? Surely IIS should recompile a page if its modified date
    > changes,


    Should != does. Did you restart IIS?
     
    Aaron [SQL Server MVP], Nov 18, 2004
    #5
  6. MikeT

    MikeT Guest

    On Thu, 18 Nov 2004 09:42:49 -0500, "Aaron [SQL Server MVP]"
    <> wrote:

    >> the two pages? Surely IIS should recompile a page if its modified date
    >> changes,

    >
    >Should != does. Did you restart IIS?
    >


    I tried this at lunchtime - no difference to the pages at all:
    anything using the original name is slow when using the
    filesystemobject, the same code under a new name runs at normal
    speed. This is getting silly.

    Mike
     
    MikeT, Nov 18, 2004
    #6
  7. See the last section of http://www.aspfaq.com/2022 ... you may be able to
    resolve this by dropping the application and re-creating it.

    --
    http://www.aspfaq.com/
    (Reverse address to reply.)




    "MikeT" <9.co.uk> wrote in message
    news:...
    > On Thu, 18 Nov 2004 09:42:49 -0500, "Aaron [SQL Server MVP]"
    > <> wrote:
    >
    > >> the two pages? Surely IIS should recompile a page if its modified date
    > >> changes,

    > >
    > >Should != does. Did you restart IIS?
    > >

    >
    > I tried this at lunchtime - no difference to the pages at all:
    > anything using the original name is slow when using the
    > filesystemobject, the same code under a new name runs at normal
    > speed. This is getting silly.
    >
    > Mike
     
    Aaron [SQL Server MVP], Nov 18, 2004
    #7
  8. MikeT wrote:
    > On Thu, 18 Nov 2004 09:42:49 -0500, "Aaron [SQL Server MVP]"
    > <> wrote:
    >
    >>> the two pages? Surely IIS should recompile a page if its modified
    >>> date changes,

    >>
    >> Should != does. Did you restart IIS?
    >>

    >
    > I tried this at lunchtime - no difference to the pages at all:
    > anything using the original name is slow when using the
    > filesystemobject, the same code under a new name runs at normal
    > speed. This is getting silly.
    >
    > Mike

    What are the filenames? (grasping at straws)
    --
    Microsoft MVP -- ASP/ASP.NET
    Please reply to the newsgroup. The email account listed in my From
    header is my spam trap, so I don't check it very often. You will get a
    quicker response by posting to the newsgroup.
     
    Bob Barrows [MVP], Nov 18, 2004
    #8
  9. MikeT

    Mark Schupp Guest

    See Aaron's response. If that doesn't help:

    Is the slow page slow when called a second time with the same parameters?
    Does it make a difference which page is called first?

    restart web-server (re-boot if possible)
    1. call slow page
    2. call fast page
    restart web-server again
    3. call fast page
    4. call slow page

    --
    Mark Schupp
    Head of Development
    Integrity eLearning
    www.ielearning.com


    "MikeT" <9.co.uk> wrote in message
    news:...
    > On Thu, 18 Nov 2004 09:42:49 -0500, "Aaron [SQL Server MVP]"
    > <> wrote:
    >
    > >> the two pages? Surely IIS should recompile a page if its modified date
    > >> changes,

    > >
    > >Should != does. Did you restart IIS?
    > >

    >
    > I tried this at lunchtime - no difference to the pages at all:
    > anything using the original name is slow when using the
    > filesystemobject, the same code under a new name runs at normal
    > speed. This is getting silly.
    >
    > Mike
     
    Mark Schupp, Nov 18, 2004
    #9
  10. MikeT

    MikeT Guest

    On Thu, 18 Nov 2004 11:19:25 -0500, "Bob Barrows [MVP]"
    <> wrote:

    >MikeT wrote:
    >> On Thu, 18 Nov 2004 09:42:49 -0500, "Aaron [SQL Server MVP]"
    >> <> wrote:
    >>
    >>>> the two pages? Surely IIS should recompile a page if its modified
    >>>> date changes,
    >>>
    >>> Should != does. Did you restart IIS?
    >>>

    >>
    >> I tried this at lunchtime - no difference to the pages at all:
    >> anything using the original name is slow when using the
    >> filesystemobject, the same code under a new name runs at normal
    >> speed. This is getting silly.
    >>
    >> Mike

    >What are the filenames? (grasping at straws)


    The slow ones are called gallery.asp and model.asp - both sub frames
    of a simple two frame default.asp.

    I copied the files and named them gallery2.asp and model2.asp and then
    linked those names instead in the default.asp page to end up with a
    normal running app.

    So - I've 'fixed' the problem but still no closer to tracking this
    down. Off to try Aaron's suggestion from the FAQ.

    Mike
     
    MikeT, Nov 18, 2004
    #10
  11. MikeT

    MikeT Guest

    On Thu, 18 Nov 2004 08:42:29 -0800, "Mark Schupp" <>
    wrote:

    >See Aaron's response. If that doesn't help:
    >
    >Is the slow page slow when called a second time with the same parameters?
    >Does it make a difference which page is called first?
    >
    >restart web-server (re-boot if possible)
    >1. call slow page
    >2. call fast page
    >restart web-server again
    >3. call fast page
    >4. call slow page


    OK Tried Aaron's idea, no joy.

    But whilst I was logged into the webserver I checked the page
    permissions again - the "slow" page was using a domain IUSR account we
    set up ages ago when the libraries were on a different server to the
    current one. The "fast" page was using the default local IUSR account.
    The library itself couldn't care less as it has Everyone: read
    permissions.

    So - the speed difference is caused by the different authentication
    methods. Each and every reference to oFile.Name was costing me lots of
    time when using a domain account. Ouch. Teach me to use such similar
    account names.

    Thanks for all the help folks. There's nobody here to talk these sort
    of problems through with, and sometimes that's the only way to solve
    them.

    Mike
     
    MikeT, Nov 18, 2004
    #11
  12. MikeT

    Mark Schupp Guest

    Aaron,

    this sounds like a keeper. you do have a category on aspfaq for "weird and
    mystifying" stuff don't you?

    --
    Mark Schupp
    Head of Development
    Integrity eLearning
    www.ielearning.com


    "MikeT" <9.co.uk> wrote in message
    news:...
    > On Thu, 18 Nov 2004 08:42:29 -0800, "Mark Schupp" <>
    > wrote:
    >
    > >See Aaron's response. If that doesn't help:
    > >
    > >Is the slow page slow when called a second time with the same parameters?
    > >Does it make a difference which page is called first?
    > >
    > >restart web-server (re-boot if possible)
    > >1. call slow page
    > >2. call fast page
    > >restart web-server again
    > >3. call fast page
    > >4. call slow page

    >
    > OK Tried Aaron's idea, no joy.
    >
    > But whilst I was logged into the webserver I checked the page
    > permissions again - the "slow" page was using a domain IUSR account we
    > set up ages ago when the libraries were on a different server to the
    > current one. The "fast" page was using the default local IUSR account.
    > The library itself couldn't care less as it has Everyone: read
    > permissions.
    >
    > So - the speed difference is caused by the different authentication
    > methods. Each and every reference to oFile.Name was costing me lots of
    > time when using a domain account. Ouch. Teach me to use such similar
    > account names.
    >
    > Thanks for all the help folks. There's nobody here to talk these sort
    > of problems through with, and sometimes that's the only way to solve
    > them.
    >
    > Mike
     
    Mark Schupp, Nov 18, 2004
    #12
  13. MikeT

    MikeT Guest

    On Thu, 18 Nov 2004 09:15:54 -0800, "Mark Schupp" <>
    wrote:

    >Aaron,
    >
    >this sounds like a keeper. you do have a category on aspfaq for "weird and
    >mystifying" stuff don't you?


    When I have more time tomorrow, I'll see if I can narrow down the
    behaviour to see exactly what the difference is, but the two major
    gotchas are:

    1) if you set things like the anonymous account used for
    authentication on a page and then delete that page, a new page with
    the name will inherit the old settings.

    2) the filesystemobject appears to authenticate with every access to
    an object. Well, at least, that is the only explanation I can find for
    the behaviour I'm seeing. I'm going to be much more careful about
    making lots of fso calls inside loops from now on - I've got a bunch
    of other pages that I just thought were inherently slow that I'm going
    to go back through now. The most useful page searches through around a
    terabyte of Photoshop files so if I can speed that up, I'll be a very
    happy man.

    Mike
     
    MikeT, Nov 18, 2004
    #13
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