Re: Question about the implementation of bucket_straw_choose in src/crush/mapper.c

[zhurongze <zrz4ceph@gmail.com>]

于 2012年03月29日 17:16, 胡瀚森 写道:
> Hi everyone, i'm proceeding reading source code of crush
>
> i'm reading src/crush/mapper.c which is describing the core
> implementation of crush alg.
> in reading function bucket_straw_choose, i compare the implementation
> with the idea written in the thesis and have some problem
> understanding it.
>
> in the thesis, it said that the length of straw should multiply the
> weight of bucket item so that heavier items are more likely to be
> selected.
> in bucket_straw_choose, i see bucket->straws multiplying the hash value only.
>
> next, i referred to crush.h to take a look at the data structure of
> crush_bucket_straw, and found two members named 'straws' and
> 'item_weights'.
>
> i just don't know whether 'weight' and 'straw' in the implementation
> mean the same thing as in thesis. if so, why item_weights is not used
> in bucket_straw_choose.
>
> Thanks.
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Are you chinese?  I wrote 2 articles about  CRUSH design and source code 
analysis in Chinese, I think this is useful for you.
The Link is http://toplab.sinaapp.com
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