Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool

[Gerd Hoffmann]

Andrea Arcangeli wrote:
> On Thu, Dec 11, 2008 at 05:11:08PM +0100, Gerd Hoffmann wrote:
>> Yes.  But kernel aio requires O_DIRECT, so aio users are affected
>> nevertheless.
> 
> Are you sure? It surely wasn't the case...

Tons of docs say so, but might be they are wrong, I didn't check.

>> Kernel side looks easy, attached patch + syscall table windup in all
>> archs ...
> 
> So should we depend on this?

I suspect we will end up with multiple implementations anyway.

So one could be preadv+threads.  Probably quite portable if we manage to
get the syscalls into linux kernel and glibc.  All *BSDs have it
already, for solaris I've found a feature request on that.  Dunno for MacOS.

Additionally we could have OS-specific bits such as linux-aio.  Maybe
also posix-aio for the *BSD family in case their kernel support for that
is better than what glibc provides (i.e. can handle multiple requests in
parallel without the fdpool hack).

cheers,
  Gerd