> As far as I understand what happens when I start a Linux program, the
> executable file is mmaped into memory and the execution of the code
> itself prompts Linux to load the required pages of the program.
>
> I expect that this could cause unwanted delays during program execution
> when a function that has never been used (nor loaded into memory) is
> called. This delay could be bigger than 10ms while the 2.6 kernel is
> usually quite predictable thanks to Ingo Molnar and others' work.
>
> Is Linux really using on-demand loading ?
Yes.
> Is it very different from what I described in the first paragraph ?
No, not really (it's not different). The pages are mapped, and brought
in via page faults. There is read-ahead code, so if you start hitting
sequential pages, it'll read more than is immediately necessary in the
hope of keeping up.
> Can on-demand loading be disabled ? (This would seem convenient for my
> applications since I generally start a program that is meant to run as
> predictably as possible for months.)
Well, the easy way to disable on-demand loading is munmap().
Then the data won't be loaded and you'll get SIGSEGV.
However, I don't think that's what you mean.
If you want to keep code in memory, so it can't suffer a page
fault, either on initial load or by being swapped out to make
room for something else, use mlock() or mlockall().
If you just want to encourage (but not *insist*) code to be in memory,
I think Linux implements madvise(MADV_WILLNEED) sensibly.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
