PVE 5.1 and ZFS, L2 ARC header size not shown

mbaldini

Well-Known Member
Nov 7, 2015
170
22
58
Hello.

I'm starting to update various servers from 5.0 to PVE 5.1, in most of them I have ZFS and a L2 ARC cache on SSD or NVME, usually I check arcstats l2_hdr_size to see if l2 arc header is using too much of my ARC memory.
With the new ZFS packages and kernel mod version 0.7.2-1 (from /sys/module/zfs/version) I have to report that l2_hdr_size is always 0, even if cache device is used.

Cache device is enabled and used:
Code:
$ zpool iostat -v
               capacity     operations     bandwidth
pool         alloc   free   read  write   read  write
-----------  -----  -----  -----  -----  -----  -----
rpool        18.3G  3.61T      0     25  2.98K   309K
  mirror     9.22G  1.80T      0     11  1.53K   126K
    sda2         -      -      0      5    795  63.2K
    sdb2         -      -      0      5    771  63.2K
  mirror     9.05G  1.80T      0     14  1.45K   183K
    sdc2         -      -      0      7    750  91.3K
    sdd2         -      -      0      7    736  91.3K
cache            -      -      -      -      -      -
  nvme0n1p3   569M  79.4G      0      1     26   116K
-----------  -----  -----  -----  -----  -----  -----


ARC is being used, actually low use because it's a test server with only a idle Windows VM
Code:
$ arcstat
    time  read  miss  miss%  dmis  dm%  pmis  pm%  mmis  mm%  arcsz     c
18:38:59     0     0      0     0    0     0    0     0    0   1.4G   24G

Content of arcstats, l2_hdr_size is 0
Code:
$ cat /proc/spl/kstat/zfs/arcstats | grep l2_
evict_l2_cached                 4    0
evict_l2_eligible               4    199680
evict_l2_ineligible             4    2048
evict_l2_skip                   4    0
l2_hits                         4    0
l2_misses                       4    679711
l2_feeds                        4    423232
l2_rw_clash                     4    0
l2_read_bytes                   4    0
l2_write_bytes                  4    2450306048
l2_writes_sent                  4    66737
l2_writes_done                  4    66737
l2_writes_error                 4    0
l2_writes_lock_retry            4    13
l2_evict_lock_retry             4    0
l2_evict_reading                4    0
l2_evict_l1cached               4    125079
l2_free_on_write                4    6135
l2_abort_lowmem                 4    0
l2_cksum_bad                    4    0
l2_io_error                     4    0
l2_size                         4    875388416
l2_asize                        4    597329920
l2_hdr_size                     4    0

Is something changed from older version of ZFS?
I'm on the latest upgrades
Code:
$ pveversion -v
proxmox-ve: 5.1-25 (running kernel: 4.13.4-1-pve)
pve-manager: 5.1-36 (running version: 5.1-36/131401db)
pve-kernel-4.13.4-1-pve: 4.13.4-25
pve-kernel-4.10.17-4-pve: 4.10.17-24
pve-kernel-4.10.17-2-pve: 4.10.17-20
libpve-http-server-perl: 2.0-6
lvm2: 2.02.168-pve6
corosync: 2.4.2-pve3
libqb0: 1.0.1-1
pve-cluster: 5.0-15
qemu-server: 5.0-17
pve-firmware: 2.0-3
libpve-common-perl: 5.0-20
libpve-guest-common-perl: 2.0-13
libpve-access-control: 5.0-7
libpve-storage-perl: 5.0-16
pve-libspice-server1: 0.12.8-3
vncterm: 1.5-2
pve-docs: 5.1-12
pve-qemu-kvm: 2.9.1-2
pve-container: 2.0-17
pve-firewall: 3.0-3
pve-ha-manager: 2.0-3
ksm-control-daemon: 1.2-2
glusterfs-client: 3.8.8-1
lxc-pve: 2.1.0-2
lxcfs: 2.0.7-pve4
criu: 2.11.1-1~bpo90
novnc-pve: 0.6-4
smartmontools: 6.5+svn4324-1
zfsutils-linux: 0.7.2-pve1~bpo90
 
not the case here:
Code:
cat /proc/spl/kstat/zfs/arcstats | grep l2_
evict_l2_cached                 4    15819211264
evict_l2_eligible               4    54116298752
evict_l2_ineligible             4    16418545664
evict_l2_skip                   4    0
l2_hits                         4    3092
l2_misses                       4    5918210
l2_feeds                        4    238925
l2_rw_clash                     4    0
l2_read_bytes                   4    19409920
l2_write_bytes                  4    10497453568
l2_writes_sent                  4    180396
l2_writes_done                  4    180396
l2_writes_error                 4    0
l2_writes_lock_retry            4    0
l2_evict_lock_retry             4    0
l2_evict_reading                4    0
l2_evict_l1cached               4    0
l2_free_on_write                4    179
l2_abort_lowmem                 4    0
l2_cksum_bad                    4    0
l2_io_error                     4    0
l2_size                         4    15513328128
l2_asize                        4    9990983680
l2_hdr_size                     4    175798656
 

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