Re: udev hangs under high loads

[Kay Sievers <kay.sievers@vrfy.org>]

On Sun, Oct 24, 2004 at 12:27:30PM -0700, Kevin P. Fleming wrote:
> Olaf Hering wrote:
> 
> >I had not time yet to look at the udev locking bugs.
> 
> I too would be unhappy if udev was wasting this much memory for extra 
> files related to my /dev nodes (I moved to udev precisely to avoid 
> problems like this <G>).

Just use a "normal" filesysten then and everything is fine.

> Not having looked at the code my suggestion may be way off-base, but 
> wouldn't a very simple database that supports _only_ append operations 
> (no in-place editing) suffice for udev's needs? There are many 
> applications (BIND, Zope, etc.) that work just fine with databases like 
> this, where any new or changed record is appended to the file, then 
> pointers are updated to reflect the new record's presence. Seems to me 
> that given the very small amount of update activity to udev's database 
> (for most systems it will be 95+% appends when the system boots, and 
> very little activity after that) that the small amount of wasted space 
> due to "dead" records being in the database would be acceptable.

What does "update pointers" mean? How do you manage the concurrent writing
to this file if you have several thousand processes. What would _you_ do
different from the tdb code? Please be more precise.

> Then again, some of the threads about this issue seemed to relate to 
> multiple systems sharing the same /dev directory over NFS, which I don't 
> understand at all... Why would someone even want to do that (i.e. what 
> would the value be)? If changes were made to handle non-locking-capable 
> mounts for /dev, IMHO those changes should be reverted, and the 
> documentation updated to say that if someone wants to use udev in such a 
> situation, they are on their own :-)

Please read the code before making suggestions here.

Thanks,
Kay


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