On 04/02/2016 05:33, Peter Jeremy wrote:
On 2016-Feb-03 18:23:13 +1030, Shane Ambler <free...@shaneware.biz> wrote:
Any chance you get high wired allocations?
A high wired allocation is normal for ZFS - ARC shows up as "wired"
memory.
Sometimes several times in a day I see the wired amount shown in top
rise to over 6GB (of 8GB) bringing the system to a crawl. When wired
gets over 7GB the system rarely recovers.
The ARC limit defaults to 1GB less than physical RAM so 6GB wired on
an 8GB system isn't unexpected (my home system currently has 30GB
wired out of 32GB). If this is causing problems for your workload, it
sounds like you may need to explicitly reduce vfs.zfs.arc_max (note
that this is a soft limit).
I have vfs.zfs.arc_max=2G - and now realise I also had set
vfs.zfs.arc_min=500M some time ago. Don't recall where I got it but I
also have vfs.zfs.dirty_data_max=200M
Going by figures shown in top, ARC is usually in the 1500M to 2000M
range but when wired gets over 6GB I often see ARC drop to 500MB which
I now realise matches arc_min.
When wired gets over 6GB apps start to stop responding, I then try to
push out some wired by running a script that allocates 4G, 9 times out
of 10 this drops wired to under 4GB and everything keeps working.
If I notice wired over 7GB there's usually no recover. I don't always
get to see the figures before it totally locks up.
On desktop1 I leave a terminal running top and another ready to run my
script to allocate some ram. When an app stops responding I go to
desktop1 and depending on what I see I manually allocate some ram to
flush things out.
Currently I have an uptime of 9 days 9 hours - I have manually allocated
4GB 30 times in that time.
--
FreeBSD - the place to B...Software Developing
Shane Ambler
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