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.

Low memory

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.

Back to index.