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Hans Reiser wrote:
> Mike Benoit wrote:
> 
>> This seems strange, because to me this type of workload would lend
>> itself to being less fragmented then most workloads. All the box does is
>> records TV programs, so over the course of 30-60min periods I would
>> guess 95+% of the writes are sequential. 
>>
>> Why would the fragmentation be so bad? Is there a way to tell what the
>> fragmentation rate is?
>>
>> Thanks.
>>
>>  
>>
> I wonder how the bitmap optimizations that Jeff added handle this usage
> pattern.  Jeff?

That's certainly interesting. The bitmap hinting code should skip bitmap
blocks with fewer blocks that are being asked for. The first zero hint
patch was never applied to mainline. I have that in my queue as well.

Try using the attached patch. It directs the block allocator to start
the search at the first known 0 bit rather than scanning the entire
block to find it. I'm not sure if will have a meaningful performance
impact, but it's worth a try.

- -Jeff

- --
Jeff Mahoney
SUSE Labs
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