> After scalability problems have been detected when using the sysV ipcs, I
> have proposed to use an RCU based implementation of the IDR api instead (see
> threads
http://lkml.org/lkml/2008/4/11/212 and
>
http://lkml.org/lkml/2008/4/29/295).
>
> This resulted in many people asking to convert the idr API and make it
> rcu safe (because most of the code was duplicated and thus unmaintanable
> and unreviewable).
>
> So here is a first attempt.
>
> The important change wrt to the idr API itself is during idr removes:
> idr layers are freed after a grace period, instead of being moved to the
> free list.
>
> The important change wrt to ipcs, is that idr_find() can now be called
> locklessly inside a rcu read critical section.
>
> Here are the results I've got for the pmsg test sent by Manfred:
>
> 2.6.25-rc3-mm1 2.6.25-rc3-mm1+ 2.6.25-mm1 Patched 2.6.25-mm1
> 1 1168441 1064021 876000 947488
> 2 1094264 921059 1549592 1730685
> 3 2082520 1738165 1694370 2324880
> 4 2079929 1695521 404553 2400408
> 5 2898758 406566 391283 3246580
> 6 2921417 261275 263249 3752148
> 7 3308761 126056 191742 4243142
> 8 3329456 100129 141722 4275780
>
> 1st column: stock 2.6.25-rc3-mm1
> 2nd column: 2.6.25-rc3-mm1 + ipc patches (store ipcs into idrs)
> 3nd column: stock 2.6.25-mm1
> 4th column: 2.6.25-mm1 + this pacth series.
>
