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SubjectRe: multiply files in one (was GNU/Linux stance by Richard Stallman)
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The point here is that even with all the readahead in the world, the disk
is still the slowest part of the system. If you can reduce the about of
data (number of sectors) you need to get off of the drive you win. It
doesn't matter that they will then take up the same amount of space im
memory becouse memory is fast.

example
512 100 byte (ave size) files

with the tarfs you have
1 inode
~50 blocks (which are probably togeather as it is one file)

with ext2fs you have
512 inodes
512 blocks (which may be scattered as they are all seperate files)

so with tarfs you are reading 51 blocks rather then 1024 blocks a 20:1
advantage! (in real life milage will vary of course)

when reading this is a hugh advantage. when writing you need support at
the filesystem level (like reiserfs is doing) so that writes can be done
reasonably. (probably something along the lines of treat the files in
memory as normal files and they dn't get mashed back togeather until the
buffers are flushed and they get written back to disk)

David Lang


On Mon, 29 Mar 1999, Larry McVoy wrote:

> Date: Mon, 29 Mar 1999 22:15:14 -0800
> From: Larry McVoy <lm@bitmover.com>
> To: Richard Gooch <rgooch@atnf.csiro.au>
> Cc: linux-kernel@vger.rutgers.edu
> Subject: Re: multiply files in one (was GNU/Linux stance by Richard Stallman)
>
> : But those were just done under SunOS, right? I wonder whether your
> : results reflect that tarfs is a very good idea, or that SunOS is
> : slow. This reminds me of the recurrent "let's implement swapfs for
> : Linux" thread. Swapfs is good for SunOS because SunOS is slow. Swapfs
> : for Linux is probably pointless because ext2fs and Linux are so fast.
>
> Do the math. If you did the math, instead of asking me to do the math,
> then you would already know the answer. I find this whole conversation
> extremely frustrating. Nothing I tell you is good enough and when I
> tell you to go reason it out and come up with the same (or different,
> I could care less which) answers on your own, you come back and ask
> me to tell you again what I've already told you. That's an endless
> loop and only you can break out of it - go think about it. Model it.
> Figure out exactly how long it takes to read a bunch of little files
> all in their own blocks and contrast that with how long it would take
> to read all those blocks in one large I/O.
>
> I can't think for you. Please think for yourself and then we can have
> a reasonable (and very enjoyable, I might add) conversation.
>
> -
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>

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