Messages in this thread |  | | | Date | 30 Jan 2006 07:00:11 -0500 | | From | linux@horizon ... | | Subject | Re: Can on-demand loading of user-space executables be disabled ? |
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> 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 majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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