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Old 09-21-08, 02:01 PM   #5
norbot
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Join Date: Feb 2007
Posts: 9
Default Re: zfs and nvidia on FreeBSD x86?

A little background. The kmem setting controls how much memory is available for various kernel tasks. kmem is a shared memory pool. If one kernel task uses a lot, less is available to others. When the kernel runs of this type of memory, it panics and crashes.

Kernel tasks typically use different amounts of kmem at different times. They will allocate more when they need it and release it when they are done. ZFS is very hungry for this type of memory. The "arc" settings try to put a limit on how much ZFS will try to claim. Unfortunately, these limits are not absolute, they are targets. ZFS will sometimes exceed these limits for short periods of time.

In my workload (general desktop), another large consumer of kmem is the nvidia driver. The driver will allocate kmem to support graphic applications. When I experience panics, it is typically because both ZFS and nvidia are exerting memory pressure at the same time.


Quote:
Originally Posted by spaghetti View Post
when you say reasonable uptimes do you mean days, weeks or months...?
Many days if I am careful about what I am doing.


Quote:
Originally Posted by spaghetti View Post
When it finally does crash is there any risk of data corruption?
I use ZFS for (almost) everything. ZFS is very robust when it comes to crashes. I have not yet experienced any data loss or corruption.

ZFS is great. This the reason why I subject myself to this instability. It is very unfortunate that ZFS and nvidia do not play nicely together. If only the nvidia driver supported larger KVA_PAGES settings ...
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