ZFS slowness (not using cache?)
davidt at yadt.co.uk
Sun Nov 4 05:18:37 PST 2007
On Sun, 04 Nov 2007, Kris Kennaway wrote:
> David Taylor wrote:
>>Hmm. That prompted me to have a look at the arcstats, and I'm now rather
>>confused. It seems to have plenty of cache free, but not actually using
>>I'm running i386 for now (on an amd64 motherboard), with 4GB of RAM
>>(~3.5Gb usable) and the following settings in loader.conf:
>>This results in (sysctl):
>>vm.kmem_size_max: 335544320 # I have just noticed this is about 300MB,
>> # far lower than vm.kmem_size. Is that a
> No but you can't set kmem to 1500MB without first increasing the kernel
> address space (1GB on i386) to some suitably larger value via KVA_PAGES.
Sorry, I should have mentioned that I have KVA_PAGES=512.
>>Regardless of what I do, I can't seem to get arcstats.size to exceed
>>100MB. It initially goes up with disk usage, but then starts to
>>drop again, causing it to hold steady around 70-90MB. Something
>>seems to be agressively pushing data out of the cache, despite it
>>being <20% full, which seems rather fishy.
>>Does anyone know what's going on?
> Try increasing kern.maxvnodes.
Increasing this from 100k to 1M seems to have made no difference.
vfs.numvnodes is now growing to 150k and beyond, but arcstats.size
is still sitting at ~70MB.
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