> 2010/2/26 Otto Moerbeek <[email protected]>: > >> 2. > ... > >> I think that we may introduce some variable - sysctl variable or > >> malloc.conf flag - which will prevent sys_mmap() or uvm_map_hint() > > If fragmentation really is a problem for you, my first reaction is: > > use a machine with a bigger adress spacce. > > No deal. amd64, for example, use same semantics - 2G userspace, If I > remember correctly. > But anyhow, it is not so good way. Let's see - I have i386 machine > with 2G ram. But I can't use more than 1G because postgres's > allocations may start faililg. It is not so funny. > > Sysadmin must have the possibility to change this behavour. > > > IMO, a flag for malloc(3) is not a good idea. Memory layout policy is a > > kernel task. > So, what is better? > > > As for reducing the gaps: if gaps area few pages max, in effect you > > are reducing randomness and increasing predictability of memory > > layout. I would hate too loose that. > I said about this - yes, it reduces and increases... but "sysadmin > must have the possibility to change this". Let he decide his needs. > Again, there are cases when you NEED use memory, and you agreed to pay > reducing randomness for that. Let sysadmin decide. > > And there are already some funny sysctl's - machdep.allowaperture, > machdep.userldt. > Probably it is not so scared to add variable for "shrink randomness"? > > 2010/2/26 Theo de Raadt <[email protected]>: > > I know what you want. You, me, we all want faster software. But at > > the cost of encouraging the software to become less reliable, less > > maintainable, less debuggable? No, you don't want that. When > > software crashes, I want to be able to fix it on the spot because the > > bug is obvious. So that you don't hit the bug. > > Totally agreed. And I do not argue that current behavour must be > changed. Let it be as it is by default! > > But I just want to add POSSIBILITY to change this. Let sysadmin decide > that in some case it NEED "shrink randomness", doesn't matter which > bugs _may_ will show themselfs. > Make sysadmin hack through kernel sources is not good. > Let it be sysctl variable. Or maybe kernel config option (remember > pptp port recommendations about kernel?). It must be some switch.
No. We choose to not do that because people like you exist -- people who think they can choose between choose weakness for free, over strength with a cost. You can't choose; you'll always choose weakness. The right way to solve this is to find clever modifications for the vm system. But nooo. You just want a button to say "weaken my system". There's lots of buttons like that, provided by other operating systems.
