Re: [RFC][PATCH] Add sysfs entry that displays MSI-X IRQs

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On Wed, Feb 11, 2009 at 04:32:25PM -0800, Greg KH wrote:
> > so, on 64-bit, that's 40 bytes, plus the 16 bytes for the filename,
> > an extra 56 bytes for msi_desc.  That's basically doubling the size of
> > msi_desc (while I'd much rather shrink it).
> 
> Is 56 bytes a big deal?  How many attributes are we talking about here?
> And on what size machine?

Devices can have up to 2048 MSI-X interrupts.  I don't think we've
really decided what our usage model is -- some people are looking at
one (or two) interrupt per cpu core, some are looking at one or two per
virtual machine, others are looking at crazy things like one or two per
TCP endpoint ... I don't think we can write this off as "you only use a
lot on big machines".

> > So I have a counter-proposal.  It's a bit of work though.
> > 
> > If we give sysfs_dir_operations an open and a release method, we could
> > construct directories on the fly.  I don't think we'd want to do this
> > for all sysfs directories necessarily, but for special cases like this
> > where we have a large number of files, know there can't be duplicates,
> > and can construct the files in the directory very quickly, I think it
> > could be a big win.
> 
> I don't think it's worth the complexity, but feel free to prove me wrong
> with a patch that shows otherwise :)

All righty.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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