[asdf-devel] Faster loading for deployed systems?

[Faré]

Dear Erik,

> I am trying to implement a method of using a "batteries included" lisp image
> (ccl, linux, 64bit) which can be used for running a variety of lisp tasks in
> a batch mode. I chose to pre-load the image because it was just too slow to
> load the individual fasl files at run time, either via asdf or through a
> generated load-list.
>
At ITA, we also deliver applications as dumped images with lots of systems.
But I admit that during incremental development,
we recompile files individually with SLIME
rather than load entire systems with ASDF.

> I'm using ASDF to load a small system at run-time, but finding that even
> with small system (say, one file), performance is sluggish, over 2 seconds.
>
First, how big are that small system's dependencies?
Because they will all be scanned.
Second, how much time is spent in initialize-source-registry?
Because if you reset it when dumping an image
(which you probably should
unless the source is guaranteed to be at the same place at runtime),
it will scan all the declared source trees.

> It looks like the problem crops up when there are many dependencies. Poking
> around the asdf code this appears to be because operate always traverses the
> system dependencies, and pokes the asd files to find if they have changed.
>
> This makes sense for asdf in development mode, since it needs to discover
> changed systems. Not so good for a deployed system.
>
Well, what do you propose ASDF should do?
Have some option to operate and/or traverse
to skip checking some dependencies if they are already loaded,
kind of a :force-not complement to :force ?
I suppose I'll accept a patch that does it.

> ASDF assumes that since the system def file has not changed, the system
> hasn't been changed either (I know there has been discussion of this
> assumption.) But lets assume that at least part of the reason for that is
> because it is very time consuming to check the entire set of files every
> time the developer wants to recompile and load just a single file.
>
I don't think that's true, but my head hurts just thinking about it.

> Why not assume in a deployment mode that NO system will have changed if it
> is already loaded in memory, and unless the application has asked that it be
> reloaded? This would be for performance as well as for safety -- we really
> don't want dependency checking to result in any filesystem checks, etc.
>
Because that's wrong? I don't have as many dependencies as you do when
I reload a system with asdf, but usually, I do want the dependencies
to be reloaded.

> I feel that this problem is really pushing my grokking of asdf, but I'm
> delving ahead anyway.
>
> I haven't tested it extensively, but I did just waste a perfect sunday
> morning fiddling with this:
>
> extended module with a slot "up-to-date-p", but surely there is a better
> name, this I just chose while in early play mode:
>
> added these methods:
>
> (defmethod operation-done-p ((o load-op) (c module))
>   (module-up-to-date-p c))
>
> (defmethod mark-operation-done ((operation load-op) (c module))
>   (setf (module-up-to-date-p c) t))
>
> tweaked the operate method so that it exits early if the module has been
> marked as up-to-date
>
>  (if (operation-done-p op system)
>  (return-from operate (values op nil)))
>
> and do-traverse to only collect "kids" if it is not done
>
> (unless (operation-done-p operation c)
>  (while-collecting (internal-collect)
>
I think that's quite wrong.
How are you to maintain the up-to-date-ness of your modules?

> Note that this code goes in the special section of operate for handling
> modules.
>
> I think that is all that I did.
>
> I found that the time to handle the require for my current project dropped
> from about 2 1/2 to about 1/2 second.
>
I'd rather you implement a :force-not. It sounds cleaner to me.

> Thoughts?
>
I imagine a far future where an XCVB daemon watches changes to the filesystem
to detect which registered builds require an update. Not quite there yet.

—♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org
The older I grow, the more I distrust the familiar doctrine that age
brings wisdom.  — H.L. Mencken
(Plus je vieillis, moins je crois en l'idée commune que l'age apporte
la sagesse.)