Date: Wed, 18 Apr 2018 12:50:08 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Kees Cook <keescook@...omium.org> Cc: Michal Hocko <mhocko@...nel.org>, Andy Lutomirski <luto@...nel.org>, Laura Abbott <labbott@...hat.com>, Rasmus Villemoes <rasmus.villemoes@...vas.dk>, LKML <linux-kernel@...r.kernel.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com> Subject: Re: [PATCH v2] fork: Unconditionally clear stack on fork On Wed, 18 Apr 2018 09:38:07 -0700 Kees Cook <keescook@...omium.org> wrote: > >> So some quite careful quantitative testing is needed here, methinks. > > > > Well, I did some more with perf and cycle counts on running 100,000 > > execs of /bin/true. > > > > before: > > Cycles: 218858861551 218853036130 214727610969 227656844122 224980542841 > > Mean: 221015379122.60 > > Std Dev: 4662486552.47 > > > > after: > > Cycles: 213868945060 213119275204 211820169456 224426673259 225489986348 > > Mean: 217745009865.40 > > Std Dev: 5935559279.99 > > > > It continues to look like it's faster, though the deviation is rather > > wide, but I'm not sure what I could do that would be less noisy. I'm > > open to ideas! > > Friendly ping. Andrew, can you add this to -mm? I did so on Feb 21 but didn't merge it up because I'd told myself that careful perf testing is needed. I guess we've sufficiently ticked that box. Kind of. Maybe. Oh well, it's easy enough to revert. I'll add it to the next batch-for-Linus.
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