Re: [Qemu-ppc] 2x-3x tcg performance regression on ppc64 (maybe others)

[Peter Maydell]

On Tue, 5 Feb 2019 at 08:37, Howard Spoelstra <address@hidden> wrote:
>
>
>
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> On Fri, Feb 1, 2019 at 11:54 PM Cleber Rosa <address@hidden> wrote:
>>
>> While working on the "boot_linux_console.py" tests, after a given
>> rebase, I noticed that the ppc64 specific test began timing out.  The
>> original timeout set to the test was 60 seconds, and it "always" had
>> room to spare when running either on my system, or on Travis CI.
>>
> Hi,
>
> As reported on IRC on 31-01, performance loss also occurs with 
> qemu-system-ppc:
> "I noticed a substantial performance loss (~35% in processor benchmark) in 
> qemu-system-ppc running Mac OS 9.2. Bisecting shows that 
> https://github.com/qemu/qemu/commit/f7b78602fdc6c6e4befc90159da8e93900b4bcb1 
> introduces the issue. Reverting brings performance back."

Yeah; Mark Cave-Ayland did a bit more digging into this last night,
and I have a patch that fixes it. I'll send that in a moment when
I've confirmed that I've caught all the places we need to fold
the cluster index into the hash cflags value.

thanks
-- PMM