Programming

Yes, my program just read the file sequentially without bouncing back and forward.

I really doubt physical memory on which the application will run will have enough memory
to contain the whole file.

By the way, is there a syscall for linux to get the total amount of free physical memory?

Thanks guys for your help.

Really appreciated.

I just stumbled across linux syscall readahead().

Do you think it can be used to improve performances even further ?
Or is it just an alternative way of setvbuf ?

Thanks again.

It can improve read performance - see also preload (a system service or daemon) and madvise.

madavise seem interesting.

So it's either
mmap + madavise( MADV_SEQUENTIAL )orsetvbuf + readahead + fread

although I'm not sure I understood how readahead is supposed to be used,
that is, can I tell him I wanna read the whole file (magnitude of giga bytes)
or should I tell him chunk by chunk?

It's becoming an interesting thread btw. :-)

Thanks to all of you guys.

Yes you are on the right track as you need to figure out first the total amount of free physical memory available before you start coding the mmap call and no I don't know how to get that information on Linux but others may be able to tell you that.

I don't know Linux but I Google'd the readahead call and it seems to be the system equivalent of the mmap call. Only difference seems to be that while mmap loads the file contents into the user process readahead does the same thing but puts it all into the system buffer cache in units of pagesize.