Netsurf Cache

There was much discussion about a year ago about the cache performance on
RISC OS, and there were some code changes, but I would like to add the
results of some investigations of the Netsurf v3.4 cache on my Iyonix,
running RISC OS 5.23 (11 Oct 2015).

In the past I had problems with the cache taking large amounts of disc
space, and the resulting long backup times for !Boot, so my current
settings are 10MB space, expiring after 2 days.

However, the actual space usage was 45MB (as measured by Filer Count),
and it contained 210 files. What was more difficult to find was that
there were 7,298 directories with 8 levels, which occupied another 14MB,
of which 6,412 contained no files at any lower level. So only 886
directories actually contained the 210 files of cached data. Enumeration
of the cache took about 2 minutes.

I decided to delete all 6,412 directories that contained no data, saving
about 12MB of disc space. More importantly, counting or enumerating all
the cache now takes about 7 seconds. There are still the same number of
files and cached bytes.

Netsurf itself still seems to work, but I have not noticed any change in
performance.

So, some questions:

- When are cached files deleted to meet the configured size & expiry?
- Are directories included in the space used?
- Are directories ever deleted? If so, when?
- Will deletion of empty directories cause any problems for Netsurf?

I have looked at the help ... but that says that files are not deleted by
Netsurf, and makes no mention of directories. It also refers to a
'Perform maintenance' button which can be used to delete redundant files
... but this is nowhere to be seen!

Martin