Re: Syslets, Threadlets, generic AIO support, v6

[Jeff Garzik <jeff@garzik.org>]

Zach Brown wrote:
> I'm pleased to announce the availability of version 6 of the syslet subsystem.
> Ingo and I agreed that I'll handle syslet releases while he's busy with CFS.  I
> copied the cc: list from Ingo's v5 announcement.  If you'd like to be dropped
> (or added), please let me know.
> 
> The v6 patch series against 2.6.21 can be downloaded from:
> 
>   http://oss.oracle.com/~zab/syslets/v6/
> 
> Example applications and previous syslet releases can be found at:
> 
>  http://people.redhat.com/~mingo/syslet-patches/
>   
> The syslet subsystem aims to provide user-space with an efficient interface for
> managing the asynchronus submission and completion of existing system calls.
> 
> The only changes since v5 are small changes that I made to support the
> experimental aio patch described below.
> 
> My syslet subsystem todo list is as follows, in no particular order:
> 
>  - replace WARN_ON() calls with error handling or avoidance
>  - split the x86_64-async.patch into more specific patches
>  - investigate integration with ptrace
>  - investigate rare ./syslet-test cpu spinning
>  - provide distro kernel rpms and documentation for developers
>  - compat design problems, still? http://lkml.org/lkml/2007/3/7/523
> 
> Included in this patch series is an experimental patch which reworks fs/aio.c
> to reuse the syslet subsystem to process iocb requests from user space.  The
> intent of this work is to simplify the code and broaden aio functionality.  
> 
> Many issues need to be addressed before this aio work could be merged:
> 
>  - support cancellation by sending signals to async_threads 
>  - figure out what to do about signals from handlers, like SIGXFSZ
>  - verify that heavy loads do not consume excessive cpu or memory 
>  - concurrent dio writes
>  - cfq gets confused, share io_context amongst threads?
>  - restrict allowed operations like .aio_{r,w} methods used to
> 
> More details on this work in progress can be found in the patch.
> 
> Any and all feedback is welcome and encouraged!

You should pick up the kevent work :)

Having async request and response rings would be quite useful, and most 
closely match what is going on under the hood in the kernel and hardware.

	Jeff