On Wed, Apr 15, 2015 at 03:32:02PM -0400, Anna Schumaker wrote: > I just ran some more tests comparing the directio case across > different filesystem types. These tests used three 1G files: > 100% data, 100% hole, and mixed file with alternating 4k data and > hole segments. The mixed case seems to be consistently slower > compared to NFS v4.1, and I'm at a loss for anything I could do to > make it faster. Here are my numbers: > > ########### > # # > # XFS # > # # > ########### > > > NFS v4.1: > Trial > |---------|---------|---------|---------|---------|---------|---------| > | | 1 | 2 | 3 | 4 | 5 | Average | > |---------|---------|---------|---------|---------|---------|---------| > | Data | 1.883s | 1.808s | 1.781s | 1.685s | 1.591s | 1.746s | > | Hole | 1.815s | 1.635s | 1.682s | 1.698s | 1.653s | 1.697s | > | Mixed | 2.089s | 2.024s | 1.970s | 1.925s | 2.049s | 2.011s | > |---------|---------|---------|---------|---------|---------|---------| > > > NFS v4.2: > Trial > |---------|---------|---------|---------|---------|---------|---------| > | | 1 | 2 | 3 | 4 | 5 | Average | > |---------|---------|---------|---------|---------|---------|---------| > | Data | 1.849s | 1.879s | 1.852s | 1.799s | 1.781s | 1.832s | > | Hole | 0.668s | 0.600s | 0.611s | 0.619s | 0.617s | 0.623s | > | Mixed | 5.913s | 5.811s | 5.952s | 5.962s | 5.806s | 5.889s | > |---------|---------|---------|---------|---------|---------|---------| What that says to me is that the READ_PLUS when there are (worst case) mixed holes is either burning a lot more CPU than we expected or it is serialising somewhere (not sure where, everything in XFS should be shared locks on read/seek). Can you run a perf profile (even just a snapshot from perf top) on the server so we can see a bit about what is happening on the CPU for the different workloads? Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
