I've bumped up the zcmd size to reduce the double ioctl() calls and we're seeing 25-40% improvement clones > 1000. This is an interim fix until we get a better fix from upstream. I'm going to SRU this once we're OK with it in Arful. Attached are the new benchmarks.
** Attachment added: "Updated benchmarks comparing old and new performance stats for large numbers of clones" https://bugs.launchpad.net/ubuntu/+source/zfs-linux/+bug/1567557/+attachment/4928925/+files/zfs-clone-performance.ods -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to zfs-linux in Ubuntu. https://bugs.launchpad.net/bugs/1567557 Title: Performance degradation of "zfs clone" Status in Native ZFS for Linux: New Status in lxd package in Ubuntu: Confirmed Status in zfs-linux package in Ubuntu: Triaged Status in lxd source package in Xenial: New Status in zfs-linux source package in Xenial: New Status in lxd source package in Zesty: New Status in zfs-linux source package in Zesty: New Status in lxd source package in Artful: Confirmed Status in zfs-linux source package in Artful: Triaged Bug description: I've been running some scale tests for LXD and what I've noticed is that "zfs clone" gets slower and slower as the zfs filesystem is getting busier. It feels like "zfs clone" requires some kind of pool-wide lock or something and so needs for all operations to complete before it can clone a new filesystem. A basic LXD scale test with btrfs vs zfs shows what I mean, see below for the reports. The test is run on a completely dedicated physical server with the pool on a dedicated SSD, the exact same machine and SSD was used for the btrfs test. The zfs filesystem is configured with those settings: - relatime=on - sync=disabled - xattr=sa So it shouldn't be related to pending sync() calls... The workload in this case is ultimately 1024 containers running busybox as their init system and udhcpc grabbing an IP. The problem gets significantly worse if spawning busier containers, say a full Ubuntu system. === zfs === root@edfu:~# /home/ubuntu/lxd-benchmark spawn --count=1024 --image=images:alpine/edge/amd64 --privileged=true Test environment: Server backend: lxd Server version: 2.0.0.rc8 Kernel: Linux Kernel architecture: x86_64 Kernel version: 4.4.0-16-generic Storage backend: zfs Storage version: 5 Container backend: lxc Container version: 2.0.0.rc15 Test variables: Container count: 1024 Container mode: privileged Image: images:alpine/edge/amd64 Batches: 128 Batch size: 8 Remainder: 0 [Apr 3 06:42:51.170] Importing image into local store: 64192037277800298d8c19473c055868e0288b039349b1c6579971fe99fdbac7 [Apr 3 06:42:52.657] Starting the test [Apr 3 06:42:53.994] Started 8 containers in 1.336s [Apr 3 06:42:55.521] Started 16 containers in 2.864s [Apr 3 06:42:58.632] Started 32 containers in 5.975s [Apr 3 06:43:05.399] Started 64 containers in 12.742s [Apr 3 06:43:20.343] Started 128 containers in 27.686s [Apr 3 06:43:57.269] Started 256 containers in 64.612s [Apr 3 06:46:09.112] Started 512 containers in 196.455s [Apr 3 06:58:19.309] Started 1024 containers in 926.652s [Apr 3 06:58:19.309] Test completed in 926.652s === btrfs === Test environment: Server backend: lxd Server version: 2.0.0.rc8 Kernel: Linux Kernel architecture: x86_64 Kernel version: 4.4.0-16-generic Storage backend: btrfs Storage version: 4.4 Container backend: lxc Container version: 2.0.0.rc15 Test variables: Container count: 1024 Container mode: privileged Image: images:alpine/edge/amd64 Batches: 128 Batch size: 8 Remainder: 0 [Apr 3 07:42:12.053] Importing image into local store: 64192037277800298d8c19473c055868e0288b039349b1c6579971fe99fdbac7 [Apr 3 07:42:13.351] Starting the test [Apr 3 07:42:14.793] Started 8 containers in 1.442s [Apr 3 07:42:16.495] Started 16 containers in 3.144s [Apr 3 07:42:19.881] Started 32 containers in 6.530s [Apr 3 07:42:26.798] Started 64 containers in 13.447s [Apr 3 07:42:42.048] Started 128 containers in 28.697s [Apr 3 07:43:13.210] Started 256 containers in 59.859s [Apr 3 07:44:26.238] Started 512 containers in 132.887s [Apr 3 07:47:30.708] Started 1024 containers in 317.357s [Apr 3 07:47:30.708] Test completed in 317.357s To manage notifications about this bug go to: https://bugs.launchpad.net/zfs/+bug/1567557/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
