Re: [PATCH v3] coccicheck: process every source file at once

[Jeff King <peff@peff.net>]

On Sat, Oct 06, 2018 at 10:42:57AM +0200, René Scharfe wrote:

> > That's OK, too, assuming people would actually want to use it. I'm also
> > OK shipping this (with the "make -j" fix you suggested) and seeing if
> > anybody actually complains. I assume there are only a handful of people
> > running coccicheck in the first place.
> 
> FWIW, my development environment is a virtual machine with 1200MB RAM
> and 900MB swap space.  coccicheck takes almost eight minutes
> sequentially, and four and a half minutes with -j4.
> 
> Unsurprisingly, it fails after almost three minutes with the patch,
> reporting that it ran out of memory.  With 2900MB it fails after almost
> two minutes, with 3000MB it succeeds after a good two minutes.
> 
> time(1) says (for -j1):
> 
> 433.30user 36.17system 7:49.84elapsed 99%CPU (0avgtext+0avgdata 108212maxresident)k
> 192inputs+1512outputs (0major+16409056minor)pagefaults 0swaps
> 
> 129.74user 2.06system 2:13.27elapsed 98%CPU (0avgtext+0avgdata 1884568maxresident)k
> 236896inputs+1096outputs (795major+462129minor)pagefaults 0swaps
> 
> So with the patch it's more than three times faster, but needs more
> than seventeen times more memory.  And I need a bigger VM. :-/

Yuck. :) So if we want to take this as a complaint, then I guess we can
jump straight to implementing the fallback to the existing behavior
(though it may be worth it for you to expand your VM to get the
decreased CPU time).

I'm still puzzled by Gábor's counter-intuitive CI numbers, though.

-Peff