On Mar 18, 2016 9:41 PM, "Valdis Kletnieks" <Valdis.Kletnieks@xxxxxx> wrote:
>
> So I built linux-next next-20160417 with KASAN enabled:
Is that next-20160317?
> CONFIG_KASAN_SHADOW_OFFSET=0xdffffc0000000000
> CONFIG_HAVE_ARCH_KASAN=y
> CONFIG_KASAN=y
> # CONFIG_KASAN_OUTLINE is not set
> CONFIG_KASAN_INLINE=y
> CONFIG_TEST_KASAN=m
Which GCC version were you using? Are you sure it didn't accidentally enable the outline instrumentation (e.g. if the compiler is too old)?
> and saw an *amazing* slowdown.
Have you tried earlier KASAN versions? Is this a recent regression?
> For comparison, here is the time taken
> to reach various points in the dmesg:
>
> % grep -i free dmesg.0317*
> dmesg.0317:[ 1.560907] Freeing SMP alternatives memory: 28K (ffffffff93d3e000 - ffffffff93d45000)
> dmesg.0317:[ 12.041550] Freeing initrd memory: 10432K (ffff88003f5cb000 - ffff88003fffb000)
> dmesg.0317:[ 16.458451] ata1.00: ACPI cmd f5/00:00:00:00:00:00 (SECURITY FREEZE LOCK) filtered out
> dmesg.0317:[ 16.545603] ata1.00: ACPI cmd f5/00:00:00:00:00:00 (SECURITY FREEZE LOCK) filtered out
> dmesg.0317:[ 17.818934] Freeing unused kernel memory: 1628K (ffffffff93ba7000 - ffffffff93d3e000)
> dmesg.0317:[ 17.820234] Freeing unused kernel memory: 1584K (ffff880012c74000 - ffff880012e00000)
> dmesg.0317:[ 17.828426] Freeing unused kernel memory: 1524K (ffff880013483000 - ffff880013600000)
> dmesg.0317-nokasan:[ 0.028821] Freeing SMP alternatives memory: 28K (ffffffffaf104000 - ffffffffaf10b000)
> dmesg.0317-nokasan:[ 1.587232] Freeing initrd memory: 10432K (ffff88003f5cb000 - ffff88003fffb000)
> dmesg.0317-nokasan:[ 2.433557] ata1.00: ACPI cmd f5/00:00:00:00:00:00 (SECURITY FREEZE LOCK) filtered out
> dmesg.0317-nokasan:[ 2.439411] ata1.00: ACPI cmd f5/00:00:00:00:00:00 (SECURITY FREEZE LOCK) filtered out
> dmesg.0317-nokasan:[ 2.488113] Freeing unused kernel memory: 1324K (ffffffffaefb9000 - ffffffffaf104000)
> dmesg.0317-nokasan:[ 2.488518] Freeing unused kernel memory: 88K (ffff88002e9ea000 - ffff88002ea00000)
> dmesg.0317-nokasan:[ 2.489490] Freeing unused kernel memory: 388K (ffff88002ed9f000 - ffff88002ee00000)
Was KASAN reporting anything between these lines? Sometimes a recurring warning slows everything down.
> Only config difference was changing to CONFIG_KASAN=n.
>
> Is this level of slowdown expected? Or is my kernel unexpectedly off in the weeds?
How did it behave after the startup? Was it still slow?
Which machine were you using? Was it a real device or a VM?