support was missing in the previous version of the AIO code. More
tunables added, and very efficient support for VCHR files has been added.
Kernel threads are not used for VCHR files, all work for such files is
done for the requesting process directly. Some attempt has been made to
charge the requesting process for resource utilization, but more work
is needed. aio_fsync is still missing (but the original fsync system
call can be used for now.) aio_cancel is essentially a noop, but that
is okay per POSIX. More aio_cancel functionality can be added later,
if it is found to be needed.
The functions implemented include:
aio_read, aio_write, lio_listio, aio_error, aio_return,
aio_cancel, aio_suspend.
The code has been implemented to support the POSIX spec 1003.1b
(formerly known as POSIX 1003.4 spec) features of the above. The
async I/O features are truly async, with the VCHR mode of operation
being essentially the same as physio (for appropriate files) for
maximum efficiency. This code also supports the signal capability,
is highly tunable, allowing management of resource usage, and
has been written to allow a per process usage quota.
Both the O'Reilly POSIX.4 book and the actual POSIX 1003.1b document
were the reference specs used. Any filedescriptor can be used with
these new system calls. I know of no exceptions where these
system calls will not work. (TTY's will also probably work.)
it in struct proc instead.
This fixes a boatload of compiler warning, and removes a lot of cruft
from the sources.
I have not removed the /*ARGSUSED*/, they will require some looking at.
libkvm, ps and other userland struct proc frobbing programs will need
recompiled.
Distribute all but the most fundamental malloc types. This time I also
remembered the trick to making things static: Put "static" in front of
them.
A couple of finer points by: bde
now corrected. New tunables/instrumentation added. The code is now
likely "good enough to use." I will add the userland support soon.
The "high performance" mode for raw devices is still missing, and will
be added next. POSIX system calls that now appear to work:
aio_cancel, aio_error, aio_read, aio_return, aio_suspend, aio_write,
lio_listio. Missing, but to be added soon: aio_fsync.
POSIX.4. Additionally, there is some initial code that supports LIO.
This code supports AIO/LIO for all types of file descriptors, with
few if any restrictions. There will be a followup very soon that
will support significantly more efficient operation for VCHR type
files (raw.) This code is also dependent on some kernel features
that don't work under SMP yet. After I commit the changes to the
kernel to support proper address space sharing on SMP, this code
will also work under SMP.
