Re: [PATCH v2 4/8] scripts: add glimpse.sh for indexing the kernel

[Julia Lawall]

On Sat, 18 Jun 2016, Luis R. Rodriguez wrote:

> On Fri, Jun 17, 2016 at 05:35:26PM +0200, Julia Lawall wrote:
> > On Fri, 17 Jun 2016, Luis R. Rodriguez wrote:
> > 
> > > On Fri, Jun 17, 2016 at 11:44:26AM +0200, Julia Lawall wrote:
> > > > I'm not sure that this is worth it.  It adds a dependency on a tool that
> > > > seems not to be well maintained.  In terms of Coccinelle, I'm not sure
> > > > that it gives a big benefit.
> > > >
> > > > Attached is a graph showing the file selection time for Coccinelle for a
> > > > selection of fairly complex semantic patches.  Coccigrep is just a
> > > > line-by-line regexp search implemented in ocaml, gitgrep uses git grep.
> > > > In most cases, glimpse is clearly faster.
> > > >
> > > > On the other hand, it seems that glimpse often selects more files.
> > > > Sometimes a few more, eg 16 vs 14, and sometimes quite a lot more, eg 538
> > > > vs 236.  I suspect that this is because glimpse considers _ to be a space,
> > > > and thus it can have many false positives.  There are, however, a few
> > > > cases where glimpse also selects fewer files.
> > > >
> > > > The file processing time (ie parsing the file, searching for, matches of
> > > > the semantic patch in the file, and performing the transformation) is
> > > > normally much higher than the file selection time.
> > > >
> > > > So it seems that git grep is currently a better option for the kernel.
> > >
> > > Great, thanks, consider this patch dropped, do we want the heuristics
> > > for the cache index in place though or should I drop that as well ?
> > 
> > I assume you mean this patch:
> > 
> > [PATCH v2 3/8] coccicheck: add indexing enhancement options
> > 
> > I think it should be dropped.  It adds complexity and git grep works
> > pretty well.
> 
> Hmm but coccicheck does not make use of --git-grep even.
> 
> > If people want to use something else, they can use SPARGS,
> > or a .cocciconfig file, eg:
> > 
> > [spatch]
> > options = --use-glimpse
> 
> Neat will these be used last and thus override anything?

Good point.  If it is in the home directory, it is overrided by 
everything.  So make coccicheck shouldn't have an option related to this 
issue.

> If so, what 
> about just adding an upstream .cocciconfig with --use-gitgrep -- only 
> issue then is what if a user wants to use idutils ? How do we let them 
> override?

If we have an upstream .cocciconfig with --use-gitgrep, then the user can 
specify an SPARGS with --use-idutils and override.

If we are making an upstream .cocciconfig, I would put a timeout in it 
too.  In my experience, 120 (seconds) is fine.  Maybe 200 to give a little 
more margin.  Again, this can be overridden on the command line.

julia