* Poul-Henning Kamp <[EMAIL PROTECTED]> [000320 12:03] wrote:
> In message <[EMAIL PROTECTED]>, Alfred Perlstein writes:
> >* Poul-Henning Kamp <[EMAIL PROTECTED]> [000320 11:45] wrote:
> >> In message <[EMAIL PROTECTED]>, Alfred Perlstein writes:
> >>
> >> >Keeping the currect cluster code is a bad idea, if the drivers were
> >> >taught how to traverse the linked list in the buf struct rather
> >> >than just notice "a big buffer" we could avoid a lot of page
> >> >twiddling and also allow for massive IO clustering ( > 64k )
> >>
> >> Before we redesign the clustering, I would like to know if we
> >> actually have any recent benchmarks which prove that clustering
> >> is overall beneficial ?
> >
> >Yes it is really benificial.
>
> I would like to see some numbers if you have them.
No I don't have numbers.
Committing a 64k block would require 8 times the overhead of bundling
up the RPC as well as transmission and reply, it may be possible
to pipeline these commits because you don't really need to wait
for one to complete before issueing another request, but it's still
8x the amount of traffic.
You also complicate and penalize drivers because not all drivers
can add an IO request to an already started transaction, those
devices will need to start new transactions for each buffer instead
of bundling up the list and passing it all along.
Maybe I'm missing something.
Is there something to provide a clean way to cluster IO, can you
suggest something that won't have this sort of impact on NFS (and
elsewhere) if the clustering code was removed?
Bruce, what part of the clustering code makes you think of it as
hurting us, I thought it was mapping code?
> --
> Poul-Henning Kamp FreeBSD coreteam member
> [EMAIL PROTECTED] "Real hackers run -current on their laptop."
> FreeBSD -- It will take a long time before progress goes too far!
--
-Alfred Perlstein - [[EMAIL PROTECTED]|[EMAIL PROTECTED]]
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