Mike Galbraith wrote:
On Sun, 2008-03-30 at 16:12 +0200, Manfred Spraul wrote:
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.
Yeah, I looked at the problem, but didn't know what the heck to do about
it, so just grabbed my axe to verify/quantify.
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.
Great!
-Mike
I could get better results with the following solution:
wrote an RCU-based idr api (layers allocation is managed similarly to the radix-tree one)
Using it in the ipc code makes me get rid of the read lock taken in ipc_lock() (the one introduced in 3e148c79938aa39035669c1cfa3ff60722134535).
You'll find the results in attachment (kernel is 2.6.25-rc3-mm1).
output.25_rc3_mm1.ref.8 --> pmsg output for the 2.6.25-rc3-mm1
plot.25_rc3_mm1.ref.8 --> previous file results for use by gnuplot
output.25_rc3_mm1.ridr.8 --> pmsg output for the 2.6.25-rc3-mm1
+ rcu-based idrs
plot.25_rc3_mm1.ridr.8 --> previous file results for use by gnuplot
I think I should be able to send a patch next week. It is presently an uggly code: I copied idr.c and idr.h into ridr.c and ridr.h to go fast, so didn't do any code factorization.
Regards
Nadia