[Pvfs2-developers] bstream bucket spreading

Rob Ross rross at mcs.anl.gov
Mon Jan 21 15:24:44 EST 2008


New versions will still be able to find bstream files for files  
created by old servers? -- Rob

On Jan 18, 2008, at 12:42 PM, Pete Wyckoff wrote:

> slang at mcs.anl.gov wrote on Fri, 18 Jan 2008 11:51 -0600:
>> On Jan 17, 2008, at 3:26 PM, Pete Wyckoff wrote:
>>
>>> I just noticed this bit in trove-dbpf/dbpf.h.  The code carefully
>>> builds ((<collid> << 24) | <handleid>) then does a modulo against
>>> a power of 2, effectively stripping off all but the low bits of
>>> the handleid.
>>>
>>> The collid is not used in the hash at all.  Just in case anybody
>>> thought this was important.  I've ever only used one collection per
>>> server.
>>>
>>
>> KEYVAL_GET_BUCKET is left over from the days when we did a keyval  
>> DB per
>> file.  With just one keyval DB now, we don't use that macro --  
>> there's no
>> where in the code it gets called -- so you could safely remove it  
>> if you
>> want.
>>
>> As for BSTREAM_GET_BUCKET, that's funny that the coll-id isn't used  
>> in the
>> hash, but it turns out not to matter.  The buckets end up as  
>> directories
>> that allow us to keep the bstream directories smaller, but here  
>> too, all
>> those directories are within a directory for the entire  
>> collection.  Go
>> ahead and pull out the coll_id bits of the hash if you want.
>
> I killed the extranneous stuff.  Maybe it'll save somebody else some
> head scratching in the future.
>
> 		-- Pete
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