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[Launchpad Bug Tracker <1567557@xxxxxxxxxxxxxxxxxx>]

This bug was fixed in the package zfs-linux - 0.6.5.11-1ubuntu2

---------------
zfs-linux (0.6.5.11-1ubuntu2) artful; urgency=medium

  * Improve cloning performance for large numbers of clones (LP: #1567557)
    Bump zcmd buffer from 16K to 256K.

 -- Colin Ian King <colin.king@xxxxxxxxxxxxx>  Tue, 8 Aug 2017 17:19:21
+0100

** Changed in: zfs-linux (Ubuntu Artful)
       Status: Triaged => Fix Released

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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:
  Fix Released
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:
  Fix Released

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

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