On Tue, Sep 14, 1999 at 04:40:37PM -0400, Christopher Sedore wrote:
>
>
> On Mon, 13 Sep 1999, Jayson Nordwick wrote:
>
> > While reading through (at least trying to... I wish there was some sort of
> > kernel documentation available, the entry fee is very high) the aio_* calls,
> > I had a few questions to clear up my understanding:
> >
> > 1) Do they only work on files? The only implementation I see is in
> > the VFS layer.
>
> Any read()/write()'able descriptor should work.
>
> > 2) It is my understanding that it uses an aio daemon running as a kernel
> > thread (the aio_daemon() call kind of give that one away). It seems as
> > if this can be almost entirely done in user space. More important to what
> > I am trying to do, it seems as if aio_* does not give peak latency
> > or throughput performace, since the aio_daemon has to compete for resources
> > along with all other processes.
> >
> > Should aio_* be used for applications that have high performance
> > requirements? What does aio_* get you above having a seperate
> > thread pumping in/out data?
>
> The aio_* stuff (I use a custom patched version in 4.x) offers performance
> advantages over select() with large numbers of descriptors. In terms of
> efficiency, I don't have any trouble saturating full-duplex 100mbit link
> with aio routines on a reasonably fast box (PII-400 512MB).
>
> As more work gets done to the aio stuff, there are some potential early
> advantages available to multiprocessor machines (since the program
> 'driving' the aio could run concurrently with the kernel code moving
> network or disk data).
>
> -Chris
Do you by any change have an idea how to fix PR kern/13075
(signal is not posted for async I/O on raw devices)
Thanks,
--
Ruslan Ermilov Sysadmin and DBA of the
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