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SubjectRe: [take19 1/4] kevent: Core files.
On Tue, Oct 17, 2006 at 12:59:47AM -0500, Chase Venters (chase.venters@clientec.com) wrote:
> On Tuesday 17 October 2006 00:09, Johann Borck wrote:
> > Regarding mukevent I'm thinking of a event-type specific struct, that is
> > filled by the originating code, and placed into a per-event-type ring
> > buffer (which requires modification of kevent_wait).
>
> I'd personally worry about an implementation that used a per-event-type ring
> buffer, because you're still left having to hack around starvation issues in
> user-space. It is of course possible under the current model for anyone who
> wants per-event-type ring buffers to have them - just make separate kevent
> sets.
>
> I haven't thought this through all the way yet, but why not have variable
> length event structures and have the kernel fill in a "next" pointer in each
> one? This could even be used to keep backwards binary compatibility while

Why do we want variable size structures in mmap ring buffer?

> adding additional fields to the structures over time, though no space would
> be wasted on modern programs. You still end up with a question of what to do
> in case of overflow, but I'm thinking the thing to do in that case might be
> to start pushing overflow events onto a linked list which can be written back
> into the ring buffer when space becomes available. The appropriate behavior
> would be to throw new events on the linked list if the linked list had any
> events, so that things are delivered in order, but write to the mapped buffer
> directly otherwise.

I think in a similar way.
Kevent actually do not require such list, since it has already queue of
the ready events.

--
Evgeniy Polyakov
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