Re: Scalability requirements for sysv ipc (+namespaces broken withSEM_UNDO)

[Manfred Spraul]

Mike Galbraith wrote:
> On Sat, 2008-03-22 at 20:08 +0100, Manfred Spraul wrote:
>
>   
> > just the normal performance of 2.6.25-rc3 is abyssimal, 55 to 60% slower 
> > than 2.6.18.8:
> >     
>
> After manually reverting 3e148c79938aa39035669c1cfa3ff60722134535,
> 2.6.25.git scaled linearly
We can't just revert that patch: with IDR, a global lock is mandatory :-(
We must either revert the whole idea of using IDR or live with the 
reduced scalability.

Actually, there are further bugs: the undo structures are not 
namespace-aware, thus semop with SEM_UNDO, unshare, create new array 
with same id, but more semaphores, another semop with SEM_UNDO will 
corrupt kernel memory :-(
I'll try to clean up the bugs first, then I'll look at the scalability 
again.

--
   Manfred
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