Re: [Monotone-devel] responses to some IRC discussion of 'automate'

[Nathaniel Smith]

On Mon, Aug 07, 2006 at 12:31:50AM +0200, Thomas Moschny wrote:
> On Monday 07 August 2006 00:12 Nathaniel Smith wrote :
> > > > Why should automate stdio block size be configurable?
> > >
> > > Because it is easier to make some measurements (you asked for some
> > > benchmarks when this came up last time) this way than to recompile
> > > x-times for different values of the constant ;-)
> >
> > Sure.  (Though for simple measurement it often suffices to use a quick
> > getenv() type call, and commit it on a branch if you commit it at
> > all.)
> 
> For this small change I doubt it would have been easier to get the value from 
> the environment than from the commandline.
> 
> Additionally, some quick tests show that there is no real optimum, but 
> increasing performance with increased block size over a great range of block 
> sizes.
> 
> The ideal block size might depend on automate stdio's use: For a project like 
> Guitone that only fetches metadata through this interface, a smaller block 
> size will do, while projects like TracMonotone, that also fetches file 
> contents, a big block size can really help to increase performance.

The only advantage of a small block size is that it puts a bound on
monotone's memory use.

Most of monotone's caches are sized at a few megabytes.  I don't think
anyone will object to making the stdio block size larger than 1
kilobyte :-).

Actually, I guess there is some advantage in that if you basically
never hit the block size, it is easy for a client to have undetected
bugs in its block handling... but still.

> > Probably that's our job to adjust the default, then -- in practice I
> > can't imagine that the API's users can or will track this anywhere
> > near as well as we can.
> 
> The average user won't use automate stdio anyway.

The "user" in this case is a tool developer; we still hope that there
will be many more of them than of us :-).  And we should make it as
easy as possible for them to get good results out, without having to
learn every finicky detail of what's going on.

-- Nathaniel

-- 
"But suppose I am not willing to claim that.  For in fact pianos
are heavy, and very few persons can carry a piano all by themselves."