Messages in this thread | | | Date | Wed, 11 Feb 2004 02:09:42 +0100 (CET) | From | Maciej Zenczykowski <> | Subject | Re: your mail |
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On Tue, 10 Feb 2004, Bloch, Jack wrote:
> I have a system with 2GB of memory. One of my processes calls mmap to try to > map a 100MB file into memory. This calls fails with -ENOMEM. I rebuilt the > kernel with a few debug printk statements in mmap.c to see where the failure > was occurring it occurred in the function arch_get_unmapped_area. the code > is as follows: > > for (vma = find_vma(mm, addr); ; vma = vma->vm_next) { > /* At this point: (!vma || addr < vma->vm_end). */ > unsigned long __heap_stack_gap; > if (TASK_SIZE - len < addr) > {
it's valid there's no point in searching further for an area of at least len bytes. The user area is 0 .. TASK_SIZE-1. The addr is the address currently being checked, the len is the requested length. if addr+len is greater or equal to TASK_SIZE then the current addr (which is increasing within this loop) already causes such a mapping to overflow into kernel space (exceeds the TASK_SIZE virtual address limit). This is precisely as expected.
I'd assume your program has fragmented memory to such a level that a single consecutive 100 MB area is no longer free (not that hard to do, since TASK_SIZE is 3 GB).
Cheers, MaZe.
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