Re: [PATCH] coccicheck: optionally batch spatch invocations

>
> On Mon, May 06, 2019 at 04:34:09PM +0700, Duy Nguyen wrote:
>
> > > However, it comes at a cost. The RSS of each spatch process goes from
> > > ~50MB to ~1500MB (and peak memory usage may be even higher if make runs
> >
> > 1.5G should be fine. Trying...
> >
> > Even with no -j, my htop's RES column goes up 6GB and put my laptop in
> > "swap every bit of memory out, including the bits handling the screen"
> > mode :( I don't think it was even the peak.
>
> Interesting if you have a different version of spatch. I'm using 1.0.4
> from Debian unstable.

> Ideally we'd just invoke a single instance of spatch per rule-file and
> feed it all source files. But spatch can be rather memory hungry when
> run in this way. I measured the peak RSS going from ~90MB for a single
> file to ~1900MB for all files. Multiplied by multiple rule files being
> processed at the same time (for "make -j"), this can make things slower
> or even cause them to fail (e.g., this is reported to happen on our
> Travis builds).
>
> Instead, let's provide a tunable knob. We'll leave the default at "1",
> but it can be cranked up to "999" for maximum CPU/memory tradeoff, or
> people can find points in between that serve their particular machines.
>
> Here are a few numbers running a single rule via:
>
>   SIZES='1 4 16 999'
>   RULE=contrib/coccinelle/object_id.cocci
>   for i in $SIZES; do
>     make clean
>     /usr/bin/time -o $i.out --format='%e | %U | %S | %M' \
>       make $RULE.patch SPATCH_BATCH_SIZE=$i
>   done
>   for i in $SIZES; do
>     printf '%4d | %s\n' $i "$(cat $i.out)"
>   done
>
> which yields:
>
>      1 | 97.73 | 93.38 | 4.33 | 100128
>      4 | 52.80 | 51.14 | 1.69 | 135204
>     16 | 35.82 | 35.09 | 0.76 | 284124
>    999 | 23.30 | 23.13 | 0.20 | 1903852