Re: HEADS UP: New ZFS in the tree.

From: Nikolay Denev <ndenev_at_gmail.com>
Date: Thu, 27 Nov 2008 13:11:03 +0200
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Hi Pawel,

  I don't know if this is going to be helpful, but I did the following  
experiment :

  I've disabled all tuning in loader.conf, all values for arc_max,  
kmem_size and kmem_size_max are
  the defaults computed for amd64 machine with 4G of RAM.
  I've put debug printf()'s in the loop in vm/vm_kern.c:kern_malloc()  
printing the number of loops.
  I've increased the loop count in kern_malloc() from 8 to 100.
  I've also put debug printf()'s in the arc_lowmem() function in zfs's  
ARC cache,
  this should be the function that is called when the "vm_lowmem"  
event fires.

  Then I started one bonnie++ process and watched /var/log/messages.
  Several times the loopcount in kern_malloc() jumped from 0 to 2 or 3  
maximum, and everything
  continued to work, but after 20-30 minutes they started to increase  
steadily and it took
  the machine another maybe 20 minutes to reach 99 loops and then  
panic again with kmem_map too small.

  I hope this makes sense.

- --
Regards,
Nikolay Denev




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Received on Thu Nov 27 2008 - 10:11:09 UTC

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