On Mon, Jan 11, 2016 at 04:22:28PM -0800, Linus Torvalds wrote:

On Mon, Jan 11, 2016 at 2:07 PM, Benjamin LaHaise [off-list ref] wrote:

quoted

Another blocking operation used by applications that want aio
functionality is that of opening files that are not resident in memory.
Using the thread based aio helper, add support for IOCB_CMD_OPENAT.

So I think this is ridiculously ugly.

AIO is a horrible ad-hoc design, with the main excuse being "other,
less gifted people, made that design, and we are implementing it for
compatibility because database people - who seldom have any shred of
taste - actually use it".

But AIO was always really really ugly.

Now you introduce the notion of doing almost arbitrary system calls
asynchronously in threads, but then you use that ass-backwards nasty
interface to do so.

[ ... ]

I'm adding Ingo the to cc, because I think Ingo had a "run this list
of system calls" patch at one point - in order to avoid system call
overhead. I don't think that was very interesting (because system call
overhead is seldom all that noticeable for any interesting system
calls), but with the "let's do the list asynchronously" addition it
might be much more intriguing. Ingo, do I remember correctly that it
was you? I might be confused about who wrote that patch, and I can't
find it now.

Zach Brown and Ingo traded a bunch of ideas.  There were chicklets and
syslets?  A little search, it looks like acall was a slightly different
iteration, but the patches didn't make it off oss.oracle.com:

https://lwn.net/Articles/316806/

-chris

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