[lkml]   [2001]   [Jun]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Subjectre: disk-based fds in select/poll
Pierre Phaneuf <> wrote:
> It's fairly widely-known that select/poll returns immediately when
> testing a filesystem-based file descriptor for writability or
> readability.
> On top of this, even when in non-blocking mode, read() could block if
> the pages needed aren't in core. sendfile() behaves in a similar way.
> What would be needed to alleviate this?
> ...
> I remember seeing a suggestion by Linus for an event-based I/O
> interface, similar to kqueue on FreeBSD but much simpler. I'd just say
> "I want it too!", ok? :-)
> SGI's AIO might be a solution here, does it use threads? I'm trying to
> avoid context switching as much as possible, to keep the CPU cache as
> warm as possible.

IMHO, you want AIO. SGI's is fine for now. I hear rumors that there will be
something even better coming in 2.5, though I have no details.

Or you could use explicit userspace threads... say, divide up your
network connections among 8 or so threads. Then if one thread blocks,
the others are there to usefully soak up the CPU time.

Readiness events for readahead completion on disk files used to
seem like a neat idea to me, but now AIO seems more appealing
in the long run, since they handle random access properly.

- Dan
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 12:54    [W:0.033 / U:0.188 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site