KERNEXEC/bts: 35% slowdown

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KERNEXEC/bts: 35% slowdown

Alex Efros-4
Hi!

I'm using 4.8.17-hardened-r2, Core i7-2600K @ 4.5GHz, nvidia&virtualbox.

Because of nvidia-drivers I had to switch off CONFIG_PAX_RAP.
Because of virtualbox-modules I had to switch off CONFIG_PAX_RANDKSTACK
and CONFIG_PAX_MEMORY_UDEREF.
Because of both I can't use KERNEXEC method "or".
All other options which increase security without noticeable performance
penalty (like memory sanitize) are switched on.

The question is, while I was expecting SOME slowdown because of enabled
KERNEXEC with method "bts", I was surprised to see 35% slowdown - it this
expected to be that high, or it is a problem with my configuration?

The actual numbers for running
    make distclean && cp ../config.backup .config && time make -j8
second time after boot into single-user mode:

- with KERNEXEC/bts:
real    5m46.685s
user    36m4.736s
sys     3m26.478s
- without KERNEXEC:
real    4m17.914s
user    27m52.945s
sys     2m35.560s

--
                        WBR, Alex.

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