Re: [libvirt] NFS over RDMA small block DIRECT_IO bug

That is expected behaviour. DIRECT_IO over RDMA needs to be page aligned so that it can use the more efficient RDMA READ and RDMA WRITE memory semantics (instead of the SEND/RECEIVE channel semantics).

> I want to run my KVM guests on top of NFS over RDMA. My guests cannot create filesystems. > > Thanks, > > Andrew. > > bug report: https://bugzilla.linux-nfs.org/show_bug.cgi?id=228 > > [root@node001 mnt]# for f in 512 1024 2048 4096 8192 16384 32768 65536 131072; do dd bs="$f" if=CentOS-6.3-x86_64-netinstall.iso of=hello iflag=direct oflag=direct && md5sum hello && rm -f hello; done > > 409600+0 records in > 409600+0 records out > 209715200 bytes (210 MB) copied, 62.3649 s, 3.4 MB/s > aadd0ffe3c9dfa35d8354e99ecac9276 hello -- 512 byte block > > 204800+0 records in > 204800+0 records out > 209715200 bytes (210 MB) copied, 41.3876 s, 5.1 MB/s > 336f6da78f93dab591edc18da81f002e hello -- 1K block > > 102400+0 records in > 102400+0 records out > 209715200 bytes (210 MB) copied, 21.1712 s, 9.9 MB/s > f4cefe0a05c9b47ba68effdb17dc95d6 hello -- 2k block > > 51200+0 records in > 51200+0 records out > 209715200 bytes (210 MB) copied, 10.9631 s, 19.1 MB/s > 690138908de516b6e5d7d180d085c3f3 hello -- 4k block > > 25600+0 records in > 25600+0 records out > 209715200 bytes (210 MB) copied, 5.4136 s, 38.7 MB/s > 690138908de516b6e5d7d180d085c3f3 hello > > 12800+0 records in > 12800+0 records out > 209715200 bytes (210 MB) copied, 3.1448 s, 66.7 MB/s > 690138908de516b6e5d7d180d085c3f3 hello > > 6400+0 records in > 6400+0 records out > 209715200 bytes (210 MB) copied, 1.77304 s, 118 MB/s > 690138908de516b6e5d7d180d085c3f3 hello > > 3200+0 records in > 3200+0 records out > 209715200 bytes (210 MB) copied, 1.4331 s, 146 MB/s > 690138908de516b6e5d7d180d085c3f3 hello > > 1600+0 records in > 1600+0 records out > 209715200 bytes (210 MB) copied, 0.922167 s, 227 MB/s > 690138908de516b6e5d7d180d085c3f3 hello > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo(a)vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust(a)netapp.com www.netapp.com -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html