* Terry Lambert <[EMAIL PROTECTED]> [020624 19:58] wrote:
> Alfred Perlstein wrote:
> > * Terry Lambert <[EMAIL PROTECTED]> [020624 19:17] wrote:
> > >
> > > System V shared memory is allocated out of KVA space (annoying,
> > > but true).
> >
> > You keep saying this but the backing object allocated for sysvshm
> > is taken from either an OBJT_PHYS or OBJT_SWAP object.
>
> Uh, it's only ever an OBJT_SWAP; see line 532 of kern/sysv_shm.c.
Your sources seem to be really out of date...
Depending on the sysctl 'shm_use_phys' either an OBJT_PHYS or OBJT_SWAP
is allocated:
656 if (shm_use_phys) {
657 shm_handle->shm_object =
658 vm_pager_allocate(OBJT_PHYS, 0, size, VM_PROT_DEFAUL
T, 0);
659 } else {
660 shm_handle->shm_object =
661 vm_pager_allocate(OBJT_SWAP, 0, size, VM_PROT_DEFAUL
T, 0);
662 }
> > At what point does it eat KVA that is other than for the backing
> > data structures?
>
> It eats address space, not RAM. And even if the mappings are not
> active (which they usually are, because of LRU and processes
> accessing them shared), the pages containing the page table entries
> for each process are themselves not swappable; anything with a
> large VSZ is going to eat 1/4k pages in KVA there, too.
>
> Ask yourself where a shared memory segment lives when it's not in
> attached to one process address space, prior to you ipcrm'ing it.
> It has to remain referenced so it isn't reclaimed.
Yes, but not mapped into the kernel's address space right? right???
--
-Alfred Perlstein [[EMAIL PROTECTED]]
'Instead of asking why a piece of software is using "1970s technology,"
start asking why software is ignoring 30 years of accumulated wisdom.'
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