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Date:   Wed, 27 Jun 2018 16:08:00 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
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        Chintan Pandya <cpandya@codeaurora.org>
Subject: Re: [PATCH v4 00/17] khwasan: kernel hardware assisted address
 sanitizer
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On Tue, 26 Jun 2018 15:15:10 +0200 Andrey Konovalov <andreyknvl@google.com> wrote:

> This patchset adds a new mode to KASAN [1], which is called KHWASAN
> (Kernel HardWare assisted Address SANitizer).
> 
> The plan is to implement HWASan [2] for the kernel with the incentive,
> that it's going to have comparable to KASAN performance, but in the same
> time consume much less memory, trading that off for somewhat imprecise
> bug detection and being supported only for arm64.

Why do we consider this to be a worthwhile change?

Is KASAN's memory consumption actually a significant problem?  Some
data regarding that would be very useful.

If it is a large problem then we still have that problem on x86, so the
problem remains largely unsolved?

> ====== Benchmarks
> 
> The following numbers were collected on Odroid C2 board. Both KASAN and
> KHWASAN were used in inline instrumentation mode.
> 
> Boot time [1]:
> * ~1.7 sec for clean kernel
> * ~5.0 sec for KASAN
> * ~5.0 sec for KHWASAN
> 
> 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?