Hi all, I noticed that sysv ipc now uses very special locking: first a global rw-semaphore, then within that semaphore rcu: > linux-2.6.25-rc3:/ipc/util.c:ids->rw_mutex is a per-namespace (i.e.: usually global) semaphore. Thus ipc_lock writes into a global cacheline. Everything else is based on per-object locking, especially sysv sem doesn't contain a single global lock/statistic counter/... That can't be the Right Thing (tm): Either there are cases where we need the scalability (then using IDRs is impossible), or the scalability is never needed (then the remaining parts from RCU should be removed). I don't have a suitable test setup, has anyone performed benchmarks recently? Is sysv semaphore still important, or have all apps moved to posix semaphores/futexes? Nadia: Do you have access to a suitable benchmark? A microbenchmark on a single-cpu system doesn't help much (except that 2.6.25 is around factor 2 slower for sysv msg ping-pong between two tasks compared to the numbers I remember from older kernels....) -- Manfred --
| Tarkan Erimer | Re: Dual-Licensing Linux Kernel with GPL V2 and GPL V3 |
| Steven Rostedt | Re: Major regression on hackbench with SLUB |
| Nick Piggin | 2.6.24-rc2 slab vs slob tbench numbers |
| Paul Jackson | Re: cpuset-remove-sched-domain-hooks-from-cpusets |
git: | |
| David Miller | Re: [GIT]: Networking |
| Gerrit Renker | [PATCH 27/37] dccp: Integration of dynamic feature activation - part 2 (server side) |
| Jarek Poplawski | [PATCH] pkt_sched: Destroy gen estimators under rtnl_lock(). |
| Frans Pop | svc: failed to register lockdv1 RPC service (errno 97). |
