RE: XFS and journalling filesystems

Vilain, Sam (sam.vilain@nz.unisys.com)
Sat, 29 May 1999 06:48:19 -0400

>>XFS is 50,000 odd lines of mainframe class filing system code. Its
unlikely
>>to be the ideal fs for a small appliance or a desktop at home even if
>>it kicks butt as a server fs.
>More like 100,000 lines+. But, I'm not sure what will wind up in Linux.
>There are two directory formats (old/new) and only one should go into
Linux.
>This should save about 10K. Other stuff is on the side like the extended
>attributes and they really don't impact the main code.
>Why do lines of code restrict what makes an fs ideal for an appliance or
>desktop?

As a dangerous rule of thumb, LOC ~ code size. More code size = bigger
kernel = less (buffercache|user memory). <flamesuit>This is a fear of Linux
kernel developers - Linux ending up as slow as say, Solaris on low end
machines (even if it kicks butt on 6144-way SMP).</flamesuit>

Numbers are often good in arguments like this. ie, how big is the ext2fs
module under Linux/MIPS, compared to the xfs module under Irix? [Comparing
with Linux/i386 should probably be avoided, because i386 code is (generally)
more instructions/word, even if you need a few extra million transistors to
decode it :)].

In summary, I guess it is important that the filesystem not only performs at
incredible speeds on high end SMP, but also it's best and average case
performance on limited memory and IO machines is also good.

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