Re: reiser4: first impression (vs xfs and jfs)

[Tom Vier <tmv@comcast.net>]

On Tue, Jun 06, 2006 at 12:25:15PM -0700, Hans Reiser wrote:
> Maybe I should ask the following: is the slow drive using reiser4?  If

No, it was ext2.

> reiser4, was the slow drive image created by copying from a reiser4
> image or an ext3 image?   (Standard benchmarking mistake: creating an
> image for a test from a filesystem not the one that is being tested. 
> readdir order matters.)

Would that really make much difference?

I think the problem here is a general problem with delayed allocation,
regardless of which fs impliments it. The fs'es need to stream out writes.
If it's possible (i don't know if fs'es are allowed this info from the vfs),
i think after a short timeout of a file no longer being open for writing, it
should be written. Maybe have a longer delay for smaller files, so they pack
better. Past a certain size threshold, once a file is closed (or only opened
read-only) i think it should be flushes without much delay. Especially if
the blk dev is idle (but knowing that at the fs level may well be impossible
w/o modding the vfs api). I think linux (and other os'es) are in need of
more intelligent io scheduling (higher level than just sector elevators).

One problem with my suggestion is that apps don't always close or reopen
read-only after they write a file.

-- 
Tom Vier <tmv@comcast.net>
DSA Key ID 0x15741ECE