Re: [Xen-devel] [RFC][PATCH] Use ioemu block drivers through blktap

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Kevin Wolf writes ("Re: [Xen-devel] [RFC][PATCH] Use ioemu block drivers 
through blktap"):
> Ian Jackson schrieb:
> > If this cleanup is really necessary, then that will cause problems for
> > future runs.  If not then the cleanup isn't really necessary :-).
> 
> I think in your classification they are "not really necessary" cleanups.
> But that's no reason not to do them, right?

Yes, but to avoid gradually accumulating an ever increasing amount of
cruft, that cleanup mechanism ought to be capable of cleaning up even
`lost' garbage of one kind or another.  And once you've got such a
garbage collecting cleanup arrangement, you don't need any separate
atexit-like arrangement which cleans up specifically after the current
run.

It is best just to run the garbage collector at a suitable point.  Do
you have a garbage collector which deletes pipes from stale domains ?

> As for uniqueness, they have the domain ID as part of their filename. If
> a pipe already exists it is reused, so no real problem here, it's just
> not nice to leave too many of them lying around IMHO.

The cost of a handful of leftover pipes for a short period of time is
tiny: a few inodes and a miniscule increase in directory search time.

OTOH if you write special-case code like this then you have the costs
of writing extra code.  Code costs effort to maintain and typically
has a nonzero bug rate, causing actual problems when it goes wrong.

Ian.

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