Re: Garbage Collection with Weak References
From: J.Marsch (jeremy_at_ctcdeveloper.com)
Date: 02/19/04
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Date: Thu, 19 Feb 2004 09:48:28 -0600
Well, it could be that the initial parse of the XML is costing you temporary
memory. As Willy noted, the O/S will reclaim memory on a minimize.
Are these XML files just serialized datasets, or are they XML files that you
have created, and are "manually" reading into datasets? If it's the latter,
you might try using some different technology to read the XML files. If you
load it up as a DOM object, (at least, this is the way the COM XML parsers
work, someone correct me if .Net is different), the whole document must be
loaded into memory and parsed, so large XML files can be very expensive.
You might try an alternative technology, like SAX, which loads the XML
progressively, and fires events as new elements are read.
"Derrick" <derrick1298@excite.com> wrote in message
news:%23CNy2Rn9DHA.1428@TK2MSFTNGP12.phx.gbl...
> Thanks for the info, I had been calling GC.Collect with 0 after reading a
> little today, still didn't help.
>
> I still don't understand why the mem usage stat in windows task manager
> drops to almost nothing when the app is minimized, and then grows
relatively
> slowly upon maximizing and navigating data. Is that expected?
>
> I'm not running out of memory on my machine, but am worried about clients
> running on older machines with much less memory available. The dataset
I'm
> prototyping with is one of our smaller sets, xml file about 20m. They can
> get up to 300m....
>
> "J.Marsch" <jeremy@ctcdeveloper.com> wrote in message
> news:uZ5dqGn9DHA.340@tk2msftngp13.phx.gbl...
> > Unless you are running out of memory, I would advise that you let the GC
> do
> > it's job uninterrupted and without intervention. The application is
going
> > to use as much memory as it needs, but the GC will automatically start
> > collecting more aggressively if system memory comes under pressure.
> >
> > Oh, one other thing: Manually calling GC.Collect() might have some
> > unintended consquences for you: depending upon whats going on with your
> app
> > at the time that you call it, that might actually cause memory to be
> > released less efficiently. The GC operates on the principle that longer
> > lived objects are collected less frequently than shortlived objects, so
> each
> > time an object survives a GC (because there is a reference to it), it is
> > promoted to a higher generation. There are 3 generations: 0, 1, and 2.
> The
> > GC won't try to collect an object in generation 1 unless not enough
memory
> > was released with a gen 0 collection. Gen 2 collections are even more
> rare,
> > and are very expensive, as the GC must freeze all threads and examine
> every
> > object in memory. By calling GC.Collect() manually, you might be
> > artificially promoting some of your objects to Gen 1 or even Gen 2, and
> > thereby increasing the amount of time that the memory will be held (and
> > increasing the expense of destroying them)
> >
> > Rico Mariani (performance optimizer guy for MS) has an interesting blog
> > entry on the topic:
> > http://weblogs.asp.net/ricom/archive/2003/12/02/40780.aspx
> >
> >
> > "Derrick" <derrick1298@excite.com> wrote in message
> > news:epAnDWm9DHA.2044@TK2MSFTNGP10.phx.gbl...
> > > I'm loading a boatload of data into a DataSet. The memory usage grows
> and
> > > grows for the app while loading that data. Calling GC.Collect()
reduces
> > the
> > > consumption slightly. When I minimize the app though, the usage goes
to
> > > about 500k, and then grows when maximizing the app and working with
> > DataSet.
> > > The DataSet still appears to have all data when mem footprint was many
> > many
> > > megs at the end of loading it.
> > >
> > > Two questions:
> > > 1) I'm guessing DataSet employs weak references to all data, and that
> > weak
> > > referenced data is GC'ed when the app minimizes. Can anyone
> confirm/deny
> > > that?
> > > 2) If that is the case, is there a "GC.AgressivelyCollect()" type
call
> I
> > > can make while I'm loading data so the footprint stays in a somewhat
> sane
> > > range?
> > >
> > > Thanks in advance!
> > >
> > > Derrick
> > >
> > >
> >
> >
>
>
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