On Fri, Oct 27, 2023 at 03:34:35PM +0200, Ronald Klop wrote:
What stands out to me is that you do quite a lot of writes on the disk. (I
might be mistaken.)
The max. number of IOPS for HDD is around 80 for consumer grade harddisks. I
think this counts for USB connected disks.
https://en.wikipedia.org/wiki/IOPS#Mechanical_hard_drives
From the stats you posted it looks like you are almost always doing 50+
writes/second already. That does not leave much IOPS for the find process.
ZFS tries to bundle the writes every 5 seconds to leave room for the reads. See
"sysctl vfs.zfs.txg.timeout". Unless it has too much data to write or a sync
request comes in.
% sysctl vfs.zfs.txg.timeout
vfs.zfs.txg.timeout: 5
do I need to tune this?
Here's equivalent output from my setup (I ran periodic daily again)
#device r/s w/s kr/s kw/s ms/r ms/w ms/o ms/t qlen %b
da0 16 18 191.9 557.9 50 8 144 29 10 24
da0 107 0 699.7 0.0 52 0 0 52 1 99
da0 102 0 409.2 0.0 71 0 0 71 2 98
da0 65 6 259.6 49.4 101 143 0 105 12 101
da0 57 14 227.7 123.9 153 163 0 155 12 100
da0 40 19 158.8 285.8 205 103 0 172 12 98
da0 46 30 191.1 441.9 180 58 0 132 11 91
da0 63 4 261.6 16.1 162 250 239 170 6 112
da0 67 10 273.7 83.6 99 66 0 95 12 91
da0 32 21 129.4 177.9 223 102 0 175 5 97
da0 48 16 191.9 261.3 173 130 0 162 9 109
da0 38 19 152.2 191.3 168 61 292 139 8 104
da0 92 0 366.9 0.0 104 0 0 104 4 100
da0 73 10 291.7 87.9 76 99 0 79 12 97
da0 49 15 195.2 270.9 156 129 0 150 11 103
da0 53 15 212.3 248.3 139 128 0 137 12 92
da0 54 22 216.1 272.1 151 81 92 130 8 107
da0 80 4 320.9 16.0 74 201 125 80 3 100
da0 55 10 218.8 72.9 89 73 0 87 11 82
^C
% zpool iostat 1
capacity operations bandwidth
pool alloc free read write read write
---------- ----- ----- ----- ----- ----- -----
zroot 93.6G 818G 13 16 161K 506K
zroot 93.6G 818G 91 0 367K 0
zroot 93.6G 818G 113 0 454K 0
zroot 93.6G 818G 102 0 411K 0
zroot 93.6G 818G 98 0 422K 0
zroot 93.6G 818G 67 18 271K 171K
zroot 93.6G 818G 43 16 173K 252K
zroot 93.6G 818G 43 28 173K 376K
zroot 93.6G 818G 78 3 315K 15.9K
zroot 93.6G 818G 94 0 378K 0
zroot 93.6G 818G 103 0 414K 0
zroot 93.6G 818G 102 0 658K 0
zroot 93.6G 818G 98 0 396K 0
zroot 93.6G 818G 109 0 438K 0
zroot 93.6G 818G 101 0 404K 0
zroot 93.6G 818G 47 13 191K 91.4K
zroot 93.6G 818G 52 11 209K 126K
zroot 93.6G 818G 50 20 202K 301K
zroot 93.6G 818G 46 12 186K 128K
zroot 93.6G 818G 86 0 346K 3.93K
zroot 93.6G 818G 45 18 183K 172K
zroot 93.6G 818G 42 15 172K 343K
zroot 93.6G 818G 43 24 173K 211K
zroot 93.6G 818G 87 0 596K 0
^C
So if my observation is right it might be interesting to find out what is writing.
would ktrace and/or truss be useful? something else? The truss -p output of the
find PID produces massive amounts of output, all like this:
fstatat(AT_FDCWD,"5e70d5f895ccc92af6a7d5226f818b-81464.o",{ mode=-rw-r--r--
,inode=367004,size=10312,blksize=10752 },AT_SYMLINK_NOFOLLOW) = 0 (0x0)
with the filename changing each time
(later...)
that file is in ccache!!!
locate 5e70d5f895ccc92af6a7d5226f818b-81464.o
/var/cache/ccache/f/5/5e70d5f895ccc92af6a7d5226f818b-81464.o
maybe if I can exclude that dir (and /usr/obj) it'll lessen the periodic
runtime.
But i don't know yet whats calling find(1) when periodic daily runs. If I can,
I might be able to tell it not to walk certain heirarchies.
I had similar issues after the number of jails on my RPI4 increased and they all
were doing a little bit of writing which accumulated in quite a lot of writing.
I'm at a loss as to what's doing the writing. The system runs the following:
poudriere-devel # for aarch64 and armv7
apcupsd # for ups monitoring
vnstat # bandwidth use, writes to its db in /var/db/vnstat
sshd
exim (local)
pflogd # right now it's behind a firewall, on NAT so it's not doing
much
pf # same
ntpd
powerd
nginx # this serves the poudriere web frontend, and that's it (http-only)
syslogd
My solution was to add an SSD.
I have an nfs alternative. The LAN is 1GB. But I think the fix will be to tell
find
to not search some paths. just need to work out how to do it.
What would the effect be of increasing or decreasing the txg delta with system
performance?
--
