Re: [LSF/MM TOPIC][ATTEND] Improving async io, specifically io_submit latencies

[Ankit Jain <jankit@suse.de>]

On 03/01/2013 02:33 AM, Kent Overstreet wrote:
> On Fri, Mar 01, 2013 at 01:37:55AM +0530, Ankit Jain wrote:
>> Hi,
>>
>> I'm interested in discussing how to improve async io api in the kernel,
>> specifically io_submit latencies.
>>
>> I am working on trying to make io_submit non-blocking. I had posted a
>> patch[1] for this earlier on fsdevel and there was some discussion on
>> it. I have made some of the improvements suggested there.
>>
>> The approach attempted in that patch essentially tries to service the
>> requests on a separate kernel thread. It was pointed out that this would
>> need to ensure that there aren't any unknown task_struct references or
>> dependencies under f_op->aio* which might get confused because of the
>> kernel thread. Would this kinda full audit be enough or would be it
>> considered too fragile?
> 
> Was just talking about this.  Completely agreed that we need to do
> something about it, but personally I don't think punting everything to
> workqueue is a realistic solution.

Sure. Like you and others mentioned on this thread, there are possible
ways to solve this. I think it would be useful to discuss those and
figure out an approach to try for this, at the conference.

Thanks,
-- 
Ankit Jain
SUSE Labs