Cache usage
AWeb uses a special caching system, partially in memory and partially
on disk, to reduce the number of network accesses.
Note that the AWeb cache is a cache, not a proxy system.
This means that the cache is cleared when AWeb finishes. Also, the cache
doesn't take the HTTP expiration date into account. This might change in
later versions of AWeb.
Documents
Documents that can be displayed by AWeb are initially loaded in memory.
When the document cache is full, the least recently displayed document is
swapped out to disk, thereby freeing memory. If a swapped-out page must
be displayed again, it is swapped back into memory, thereby probably
swapping out other pages.
The swapped documents are stored in AWeb's
temporary directory. It should be
clear that this would be only meaningful if the temporary directory isn't
in RAM. So, if you are using a temporary directory in RAM, be sure to set
the document cache memory size large enough.
When the total size of swapped out documents is larger than the
document cache disk size, the least recently displayed documents
are deleted.
Images
Inlined images are treated completely differently. Images are stored in
the temporary directory when they are loaded. If the image is received
completely, the datatype will process the file, resulting in a
displayable image in chip memory (the image cache). When the
image cache is full, undisplayed images in memory are removed, but the disk
file remains. If the image must be displayed later, the disk file is
processed again, but no network access is needed.
Because the datatype locks the file, the disk file must remain while the
image is in memory.
When the total size of image files is larger than the image cache
disk size, the least recently displayed images are deleted.
To avoid crashes when running out of memory (caused by the datatypes or
other external programs), AWeb tries to leave at least some amount of
memory free. Whenever there is less memory free than a configurable minimum,
AWeb will start to swap out documents, even if the document cache isn't full
yet. Displayed documents will never be swapped out. If this still haven't
freed up enough memory, AWeb will start flushing images from memory,
even if they are being displayed. As long as the image disk cache isn't full,
they remain on disk.
Setting the cache sizes
You can set the cache sizes from the
Program 3: Cache page in the
settings requester.
If you are using a 2MB Amiga, have a look at the
2MB tips.
Otherwise, you will probably want to use a
- temporary directory in RAM;
- a document memory cache large enough,
- a document disk cache of size 0;
- a reasonably sized image memory cache (this will take
up chip memory),
- a large image disk cache.
Of course, you can use other settings if you like. You can fine-tune the
memory and disk usage by changing these settings.
If you use AWeb on a native screen, you will want to keep some chip
memory free as a work space for the datatypes.
On CyberGraphics systems images will go in fast memory, so you will
want to leave some fast memory free on those systems. The exact
amount depends on the number of colours on the CyberGfx screen, and
of course on the total amount of memory.
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