On Fri, Jun 29, 2018 at 02:45:08PM +0200, Andrey Konovalov wrote: > On Thu, Jun 28, 2018 at 9:40 PM, Andrew Morton > <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Thu, 28 Jun 2018 20:29:07 +0200 Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > > >> >> Slab memory usage after boot [2]: > >> >> * ~40 kb for clean kernel > >> >> * ~105 kb + 1/8th shadow ~= 118 kb for KASAN > >> >> * ~47 kb + 1/16th shadow ~= 50 kb for KHWASAN > >> >> > >> >> Network performance [3]: > >> >> * 8.33 Gbits/sec for clean kernel > >> >> * 3.17 Gbits/sec for KASAN > >> >> * 2.85 Gbits/sec for KHWASAN > >> >> > >> >> Note, that KHWASAN (compared to KASAN) doesn't require quarantine. > >> >> > >> >> [1] Time before the ext4 driver is initialized. > >> >> [2] Measured as `cat /proc/meminfo | grep Slab`. > >> >> [3] Measured as `iperf -s & iperf -c 127.0.0.1 -t 30`. > >> > > >> > The above doesn't actually demonstrate the whole point of the > >> > patchset: to reduce KASAN's very high memory consumption? > >> > >> You mean that memory usage numbers collected after boot don't give a > >> representative picture of actual memory consumption on real workloads? > >> > >> 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. Could you elaborate on where that SLAB overhead comes from? IIUC that's not for the shadow itself (since it's allocated up-front and not accounted to SLAB), and that doesn't take into account the quarantine, so what's eating that space? Thanks, Mark.
