[fpc-devel] Memory consumed by strings

[Mattias Gaertner]

On Sat, 22 Nov 2008 23:05:43 +0200
listmember <listmember at letterboxes.org> wrote:

> Is there a way to determine how much memory is consumed by strings by
> a running application?
> 
> I'd like to know this, in particular, for FPC ana Lazarus --to begin
> with.
> 
> And, the reason I'd like to know this is this: Whenever I suggest
> that char size be increased to 4, the idea gets opposed on the grouds
> that it will need huge memory --4 times as much.
> 
> There's of course some merit in that arguement, but I have no idea
> what it is '4 times' of.
> 
> This is not very engineer-like --it being unmeasured.
> 
> Can anyone suggest a way to measure the memory load caused by strings?

The exact amount depends on the application, but think about loading
text files of 100mb into strings. This will need at least the
100mb plus the overhead for each string (at least 12 bytes). With 2 byte
chars an extra of 100mb would be needed and with 4 byte chars 300mb
additional mem would be needed. 

For example the lazarus IDE typically holds 50 to 200mb sources in
memory. If this would be changed to unicodestring (2 byte per char) then
the IDE would need 50 to 200mb more memory. And because many time
consuming tasks are already bound by the memory bandwidth of current
computers, the IDE would become twice as slow. Do the math for 4 byte
per char.


Mattias