RE: [patch] printk subsystems

From: Tom Zanussi (
Date: Tue Apr 22 2003 - 01:00:55 EST

Perez-Gonzalez, Inaky writes:
> > From: Tom Zanussi []
> >
> > It seems to me that when comparing apples to apples, namely
> > considering the complete lifecycle of an event, ... <snip>
> >
> > While kue_send_event() in itself is very simple and efficient, it's
> > only part of the story, the other parts being the copy_to_user() ...
> Agreed - my mistake here in the comparison for leaving out that stuff.
> > event. While kue can avoid this kernel-side copy, it's not possible
> > for it to avoid the copy_to_user() since its design precludes mmapping
> > the kernel data. Again, six of one, half dozen of another. kue looks
> Sure - those things, I would say, they compensate one another,
> except for that mmap() detail that pushes the balance towards relayfs
> regarding effectiveness when delivering the messages; I think that
> at the end the difference should not be too big as the copying of
> the data in kue to user space should roughly compensate by the copying
> of the data to the relayfs buffer; after all, a copy is a copy.
> No data to back this claim though, I am just thinking a mental
> schematic of the lifetime of a bit in both systems out loud.

Right. This is what I meant when I said the two were very similar
when considering the lifetime of a single event, ignoring everything
else such as bulk processing via mmap() vs. iterating through a list,
as discussed elsewhere.

> Or, again, I am missing something ...
> Iñaky Pérez-González -- Not speaking for Intel -- all opinions are my own
> (and my fault)


Tom Zanussi <> IBM Linux Technology Center/RAS

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