Re: [PATCH v4 00/17] khwasan: kernel hardware assisted address sanitizer

[Andrey Konovalov]

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.

If you think it makes sense, I can also make separate measurements
with some workload. What kind of workload should I use?