Re: Pending AIO work/patches

From: Benjamin LaHaise
Date: Mon Jun 20 2005 - 13:11:08 EST

On Mon, Jun 20, 2005 at 05:31:54PM +0530, Suparna Bhattacharya wrote:
> (1) Updating AIO to use wait-bit based filtered wakeups (me/wli)
> Status: Updated to 2.6.12-rc6, needs review
> (2) Buffered filesystem AIO read/write (me/Ben)
> Status: aio write: Updated to 2.6.12-rc6, needs review
> Status: aio read : Needs rework against readahead changes in mainline

I've looked over the patches from today and they seem quite sane. Comments

> (3) POSIX AIO support (Bull: Laurent/Sebastian or Oracle: Joel)
> Status: Needs review and discussion ?

The latest version incorporates changes from the last round of feedback
(great work Sebastien!) and updates the library license, so people should
definately take a closer look. This includes the necessary changes for
in-kernel signal support, as well as minimal conversion done on iocbs (the
layout matches the in-kernel iocb).

A quick reading shows that most of it looks quite good. I have to stare
at the cancellation code a bit more closely, though.

> (4) AIO for pipes (Chris Mason)
> Status: Needs update to latest kernels

This likely needs a rewrite with whatever the final semaphore operations
turn out to look like, as it gets very easy to convert down() into
aio_down() and that minimises the changes to the code.

> (5) Asynchronous semaphore implementation (Ben/Trond?)
> Status: Posted - under development & discussion

I got the aio_down() variant working with cancellation now, and should be
able to post an updated series of patches against 2.6.12 shortly.

> (6) epoll - AIO integration (Zach Brown/Feng Zhou/wli)
> Status: Needs resurrection ?

What are folks thoughts in this area? Zach's patches took the approach of
making multishot iocbs possible, which helped avoid the overhead of plain
aio_poll's command setup, which was quite visible in pipetest. Zach -- did
you do any benchmarking on your aio-epoll patches?

> (7) Vector AIO (aio readv/writev) (Yasushi Saito)
> Status: Needs resurrection ?

Zach also made some noises about this recently...

"Time is what keeps everything from happening all at once." -- John Wheeler
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