qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH v3] qemu-log: add log category for MMU info


From: Alexander Graf
Subject: Re: [Qemu-devel] [PATCH v3] qemu-log: add log category for MMU info
Date: Thu, 6 Nov 2014 11:23:47 +0100



> Am 06.11.2014 um 09:11 schrieb Antony Pavlov <address@hidden>:
> 
> 
>>> Running barebox on qemu-system-mips* with '-d unimp' overloads
>>> stderr by very very many mips_cpu_handle_mmu_fault() messages:
>>> 
>>>  mips_cpu_handle_mmu_fault address=b80003fd ret 0 physical 00000000180003fd 
>>> prot 3
>>>  mips_cpu_handle_mmu_fault address=a0800884 ret 0 physical 0000000000800884 
>>> prot 3
>>>  mips_cpu_handle_mmu_fault pc a080cd80 ad b80003fd rw 0 mmu_idx 0
>>> 
>>> So it's very difficult to find LOG_UNIMP message.
>>> 
>>> The mips_cpu_handle_mmu_fault() messages appears on enabling ANY
>>> logging! It's not very handy.
>>> 
>>> Adding separate log category for *_cpu_handle_mmu_fault()
>>> logging fixes the problem.
>>> 
>>> Signed-off-by: Antony Pavlov <address@hidden>
>> 
>> Have you benchmarked the performance delta with this patch applied? Just
>> boot up a random small PPC guest that shuts down immediately and "time"
>> it with and without the patch applied.
> 
> Here is my simple benchmark.
> 
> I have used buildroot with qemu_ppc64_pseries_defconfig configuration.
> 
> After successfull rootfs image build I patched inittab for halting-after-boot:
> 
> --- a/output/images/rootfs.ext2/etc/inittab       2014-11-06 
> 10:21:25.024198993 +0300
> +++ b/output/images/rootfs.ext2/etc/inittab       2014-11-06 
> 10:20:57.089421643 +0300
> @@ -23,10 +23,11 @@
> # now run any rc scripts
> ::sysinit:/etc/init.d/rcS
> 
> -::askfirst:-/bin/sh
> +::sysinit:/sbin/halt
> +#::askfirst:-/bin/sh
> 
> # Put a getty on the serial port
> -hvc0::respawn:/sbin/getty -L  hvc0 115200 vt100 # GENERIC_SERIAL
> +#hvc0::respawn:/sbin/getty -L  hvc0 115200 vt100 # GENERIC_SERIAL
> 
> # Stuff to do for the 3-finger salute
> ::ctrlaltdel:/sbin/reboot
> 
> 
> Here is my qemu cmdline:
> 
> buildroot$ time ~/qemu.git/ppc64-softmmu/qemu-system-ppc64 -M pseries -cpu 
> POWER7 -m 256 -kernel output/images/vmlinux -append 'console=hvc0 
> root=/dev/sda' -drive file=output/images/rootfs.ext2,if=scsi,index=0 -serial 
> stdio  -nographic -monitor none
> 
> 
> I use my 'not-very-busy' AMD Opteron 6176 SE-based server for testing.
> 
> Three 'time' command outputs; qemu with "qemu-log: add log category for MMU 
> info" patch:
> 
>    real    0m39.744s
>    user    0m36.940s
>    sys     0m1.216s
> 
>    real    0m39.552s
>    user    0m37.200s
>    sys     0m0.924s
> 
>    real    0m39.585s
>    user    0m37.340s
>    sys     0m0.704s
> 
> 
> Three 'time' command outputs; qemu without "qemu-log: add log category for 
> MMU info" patch:
> 
>    real    0m39.732s
>    user    0m37.484s
>    sys     0m0.756s
> 
>    real    0m40.077s
>    user    0m37.920s
>    sys     0m0.744s
> 
>    real    0m39.766s
>    user    0m37.304s
>    sys     0m1.032s
> 
> 
> So the performance delta is less than experimental error.

Ok, works for me then :).

Ackef-by: Alexander Graf <address@hidden>

Alex




reply via email to

[Prev in Thread] Current Thread [Next in Thread]