Hans
Larry McVoy writes:
> :
> : Larry McVoy writes:
> : > : What I was getting at
> : > : was that if you pack the data together, then read-ahead will yield
> : > : more complete files, which translates to less transactions in the end.
> : >
> : > Read ahead really doesn't solve the problem for two reasons:
> : >
> : > 1) the allocation policies in almost all file systems is file
> : > centric - it's careful to get *a* file contiguous but isn't
> : > careful to get multiple files in the same directory all next
> : > to each other
> :
> : 1) is solved in reiserfs.
> :
> : >
> : > 2) even if (1) was solved, the file system needs to know that it
> : > bring in more data. If the file it is reading is 1K long,
> : > why should it brin in the next 5MB of data?
> :
> : I don't understand. How does this differ from any other sort of
> : read-ahead?
>
> We need read ahead algs on directories where the data being read ahead is
> the file data, not the directory data. I.e., I read on file in this
> directory, then the next, then the next, then the next, screw it, I'm
> reading the whole directory including all of its files.
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