Re: [PATCH v4 seccomp 5/5] seccomp/cache: Report cache data through /proc/pid/seccomp_cache

YiFei Zhu
2020-11-04T11:41:09Z

On Tue, Nov 3, 2020 at 6:29 PM Kees Cook <keescook@chromium.org> wrote:
> Yeah, this is very interesting. That there is anything measurably _slower_
> with the cache is surprising. Though with only 4 runs, I wonder if it's
> still noisy? What happens at 10 runs -- more importantly what is the
> standard deviation?

I could do that. it just takes such a long time. Each run takes about
20 minutes so with 10 runs per environment, 3 environments (native + 2
docker) per boot, and 4 boots (2 bootparam * 2 compile config), it's
27 hours of compilation. I should probably script it at that point.

> I assume this is from Indirect Branch Prediction Barrier (IBPB) and
> Single Threaded Indirect Branch Prediction (STIBP) (which get enabled
> for threads under seccomp by default).
>
> Try booting with "spectre_v2_user=prctl"

Hmm, to make sure, boot with just "spectre_v2_user=prctl" on the
command line and test the performance of that?

YiFei Zhu