zfs primarycache and secondarycache properties [PSARC/2008/393 FastTrack timeout 06/27/2008]

[Mark Maybee]

Jeff Bonwick wrote:
>>>>(1) If *anyone* wants the block cached, it is cached.
>>>>(2) If *anyone* doesn't want the block cached, it is not cached.
>>>>(3) It might or might not be cached depending who gets there first.
>>>>
>>>>To me, (1) is the only policy that makes sense, or is even defensible.
>>>
>>>Agreed.  Seems like this could be accomplished in the above scenario by 
>>>having C set L2ARC_IS_CACHEABLE when it hits in the cache.
>>>
>>
>>Indeed... and looking back at the actual webrev (instead of relying on
>>my memory) I see that Eric actually implemented something like (2)
>>above.  That is, he uses a ARC_DONT_L2CACHE flag and sets it when NC
>>gets a hit.
> 
> 
> OK.  So it seems like the solution is to invert the logic there,
> and OR in ARC_DO_L2CACHE on any secondarily-cacheable cache hit.
> Everyone cool with that?
> 
Works for me.