Re: aio completion notification?

On Wed, Jun 11, 2008, Henrik Nordstrom wrote:

> > All the callback does is read into a temp buffer, and re-schedules for
> > read IO.
>
> Yes..
>
> The point of this wakeup is to break the select/poll/epoll/kqueue sleep.

I found that in the CVS history.

> It could obviously be optimized to only call this callback if there was
> a wakeup event on the pipe (or whatever the store_dir is using). It's
> done this way because the pipe was added after the storeDirCallback()
> API framework was in place.
>
> diskd should also have a similar event descriptor, not sure it has
> today.

How would it work? The diskd queues are all sysv msgq's which can't be
polled as filedescriptors. What would wake up the main Squid process?

(I'm a big fan of removing diskd entirely btw, once the performance issues
that people complain about with aufs vs diskd are resolved.)

> Proposal: Drop storeDirCallback() (and it's corresponding
> SwapDir->callback), and let each store_dir (or driver if not having per
> cache_dir queues) register it's own wakeup event to process the
> callbacks.

We can't for diskd. Suggestions welcome.

> > http://www.creative.net.au/diffs/20080711-cacheboy-aufs-callback.diff
> >
> > It should apply against 2.6, 2.7 and 2.HEAD as well as Cacheboy-HEAD.
> > aioCheckCallbacks() is now being called much, much less frequently than
> > it was before; more in line with how many operation requests there are.
>
> If you clean it up to get rid of storeDirCallback() entirely then it's a
> +1 from me.

Ok.

> The next step is to clean up aiops to have a set of worker threads per
> store instead of the global pool it has today. Would open up for proper
> load scheduling and also make it possibe to add fault management if a
> disk fails..

Thats another problem entirely; one which I'll probably attack in cacheboy
after I sort through disassocating all the comm and aiops code from the
main source tree.

Adrian

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