On Mon, 2 Jul 2018 13:22:23 -0700 Evgenii Stepanov <eugenis@xxxxxxxxxx> wrote: > On Mon, Jul 2, 2018 at 12:21 PM, Andrew Morton > <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Mon, 2 Jul 2018 12:16:42 -0700 Evgenii Stepanov <eugenis@xxxxxxxxxx> wrote: > > > >> On Fri, Jun 29, 2018 at 7:41 PM, Andrew Morton > >> <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > >> > On Fri, 29 Jun 2018 14:45:08 +0200 Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > >> > > >> >> >> What kind of memory consumption testing would you like to see? > >> >> > > >> >> > Well, 100kb or so is a teeny amount on virtually any machine. I'm > >> >> > assuming the savings are (much) more significant once the machine gets > >> >> > loaded up and doing work? > >> >> > >> >> So with clean kernel after boot we get 40 kb memory usage. With KASAN > >> >> it is ~120 kb, which is 200% overhead. With KHWASAN it's 50 kb, which > >> >> is 25% overhead. This should approximately scale to any amounts of > >> >> used slab memory. For example with 100 mb memory usage we would get > >> >> +200 mb for KASAN and +25 mb with KHWASAN. (And KASAN also requires > >> >> quarantine for better use-after-free detection). I can explicitly > >> >> mention the overhead in %s in the changelog. > >> >> > >> >> If you think it makes sense, I can also make separate measurements > >> >> with some workload. What kind of workload should I use? > >> > > >> > Whatever workload people were running when they encountered problems > >> > with KASAN memory consumption ;) > >> > > >> > I dunno, something simple. `find / > /dev/null'? > >> > > >> > >> Looking at a live Android device under load, slab (according to > >> /proc/meminfo) + kernel stack take 8-10% available RAM (~350MB). > >> Kasan's overhead of 2x - 3x on top of it is not insignificant. > >> > > > > (top-posting repaired. Please don't) > > > > For a debugging, not-for-production-use feature, that overhead sounds > > quite acceptable to me. What problems is it known to cause? > > Not having this overhead enables near-production use - ex. running > kasan/khasan kernel on a personal, daily-use device to catch bugs that > do not reproduce in test configuration. These are the ones that often > cost the most engineering time to track down. > > CPU overhead is bad, but generally tolerable. RAM is critical, in our > experience. Once it gets low enough, OOM-killer makes your life > miserable. OK, anecdotal experience works for me. But this is all stuff that should have been in the changelog from day zero, please. It describes the reason for the patchset's existence!
