[systemd-devel] [Tracker] How to use cgroups for Tracker?

[Martyn Russell]

On 23/10/14 12:01, Lennart Poettering wrote:
> On Thu, 23.10.14 11:40, Martyn Russell (martyn at lanedo.com) wrote:
>> I don't really understand why it was developed as a half complete solution
>> if I am honest. It's not as if there are no examples to follow out there
>> (FSEvents) and it's not as if we didn't say what our user space requirements
>> were at the time.
>
> fanotify may be use in synchronous mode, which is useful for virus
> scanners. The asynchronous mode is just an addition on top, but
> unfortunately nobody looks after it.
>
> To my knowlegde apple's fsevents stuff isn't really the holy grail as
> it basically makes the kernel hang on userspace components. That's the
> wrong way round. userpsace may sync on kernel, and userspace on
> userspace, but kernel on userspace is just bad design.

 From what I could tell (from the article), it starts allocating memory 
if the buffer becomes too large while waiting on the user space app to 
sync and of course, there is a finite amount of that. It would be good 
to learn from their approach and perhaps update it slightly according to 
what we prefer in the kernel (as you say not depending on user space).

But what's also important to note is, not just ANY app can ask for those 
events, only trusted apps can - so it's not that bad for Apple. I don't 
think this would work for the Linux kernel because not everyone would be 
running Tracker. So yea, bad design for us, but not insurmountable to 
work around.

-- 
Regards,
Martyn