On Mon, Apr 01, 2013 at 07:38:43AM -0500, Serge Hallyn wrote: > Quoting Glauber Costa (glommer@xxxxxxxxxxxxx): > > Hi, > > > > Notes: > > ====== > > > > This is v2 of memcg-aware LRU shrinking. I've been testing it extensively > > and it behaves well, at least from the isolation point of view. However, > > I feel some more testing is needed before we commit to it. Still, this is > > doing the job fairly well. Comments welcome. > > Do you have any performance tests (preferably with enough runs with and > without this patchset to show 95% confidence interval) to show the > impact this has? Certainly the feature sounds worthwhile, but I'm > curious about the cost of maintaining this extra state. The reason for the node-aware LRUs in the first place is performance. i.e. to remove the global LRU locks from the shrinkers and LRU list operations. For XFS (at least) the VFS LRU operations are significant sources of contention at 16p, and at high CPU counts they can basically cause spinlock meltdown. I've done performance testing on them on 16p machines with fake-numa=4 under such contention generating workloads (e.g. 16-way concurrent fsmark workloads) and seen that the LRU locks disappear from the profiles. Performance improvement at this size of machine under these workloads is still within the run-to-run variance of the benchmarks I've run, but the fact the lock is no longer in the profiles at all suggest that scalability for larger machines will be significantly improved. As for the memcg side of things, I'll leave that to Glauber.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
