Re: New Feature Idea: Compress swap file

Emil Briggs (
Wed, 25 Feb 1998 00:37:20 -0500 (EST)

>> I'm not sure though how to check how good the correlation is,
>> particularly since the drive firmware might be doing some
>> sort of geometry translation as well.
>Usually it's quite good. Only bad block replacements and
>very strange (read: exotic) drive mappings spoil the scheme.
>But since bad block remappings are getting rarer and rarer
>(the technology keeps improving) and nobody seems to like
>exotic mappings, I think it's worth it to cluster I/O.
>(Digital Unix does it, and DEC usually researches something
>before they put a major effort into it)

Judging by the nonsequential way the block numbers were
varying in bdflush in my tests I think it could be a big
performance win then. I can see how to implement the
clustering in bdflush but I'm not sure what to do about
the swapping -- seems like there's a potential for
interference. It could be done at a lower level --
buffer block writes and then do them in an efficiently
ordered way but are there any other side effects from
doing that?


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