Re: reiser4 plugins

[Valdis.Kletnieks@vt.edu]

On Mon, 27 Jun 2005 02:07:46 CDT, David Masover said:
> > Exactly the same sort of thing - traditionally it's been more or less ignored
> > in the system accounting, because A would usually average out to causing as
> > many I/Os as B did, and they were roughly equal in cost so it was a wash.
> 
> Even if A is doing A/V work and B is programming?

I said "traditionally" - it's been a "oh well, we can't do much about it"
problem for a *long* time (for instance, time spent in an interrupt handler
has usually been charged off against whoever's timeslide the interrupt handler
took a chunk out of).  It's only been tolerated so far because (a) the costs
for both users are about equal and (b) you rarely have a heavy I/O DB and a
number cruncher on the same box, or a user doing A/V work and a user doing
programming - if it's not a single-use machine, there's *multiple* number
crunchers, DBs, or programmers, and they tend to balance out.

Said tendency can dissapear quite easily here....

> How do we get over quota errors, btw?  Can we get them from write()
> calls?  If so, I don't see a Problem(TM), just an annoyance.

One gotcha here is that it means that you can't do delayed allocation on
writes - you *have* to allocate disk space at each write and then update
the quotas. (And yes, I know that 'man 2 close' says that bad stuff can
happen to your data even after your program exits - that doesn't mean we
should go out of our way to make things worse.. ;)

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