On 04/10/2017 07:20 PM, Alex Bennée wrote: > > Cédric Le Goater <c...@kaod.org> writes: > >> On 04/07/2017 08:07 AM, Cédric Le Goater wrote: >>> On 04/07/2017 07:24 AM, Nikunj A Dadhania wrote: >>>> Cédric Le Goater <c...@kaod.org> writes: >>>> >>>>> Hello Nikunj, >>>>> >>>>> On 04/06/2017 12:22 PM, Nikunj A Dadhania wrote: >>>>>> The series enables Multi-Threaded TCG on PPC64 >>>>>> >>>>>> Patch 01: Use atomic_cmpxchg in store conditional >>>>>> 02: Handle first write to page during atomic operation >>>>>> 03: Generate memory barriers for sync/isync and load/store >>>>>> conditional >>>>>> >>>>>> Patches are based on ppc-for-2.10 >>>>>> >>>>>> Tested using following: >>>>>> ./ppc64-softmmu/qemu-system-ppc64 -cpu POWER8 -vga none -nographic >>>>>> -machine pseries,usb=off -m 2G -smp 8,cores=8,threads=1 -accel >>>>>> tcg,thread=multi f23.img >>>>> >>>>> I tried it with a Ubuntu 16.04.2 guest using stress --cpu 8. It looked >>>>> good : the CPU usage of QEMU reached 760% on the host. >>>> >>>> Cool. >>>> >>>>>> Todo: >>>>>> * Enable other machine types and PPC32. >>>>> >>>>> I am quite ignorant on the topic. >>>>> Have you looked at what it would take to emulate support of the HW >>>>> threads ? >>>> >>>> We would need to implement msgsndp (doorbell support for IPI between >>>> threads of same core) >>> >>> ok. I get it. Thanks, >>> >>>>> and the PowerNV machine ? >>>> >>>> Haven't tried it, should work. Just give a shot, let me know if you see >>>> problems. >>> >>> sure. pnv is still on 2.9, so I will rebase on 2.10, merge your >>> patches and tell you. >> >> The system seems to be spinning in skiboot in cpu_idle/relax when >> starting the linux kernel. It finally boots, but it is rather long. >> David has merged enough to test if you want to give it a try. > > Does PPC have Wait-for-irq or similar "sleeping" instructions? > > We had to ensure we were not jumping out of the cpu loop and suspend > normally.
I really don't know. Ben, now that we have mttcg activated by default on ppc, it takes a while for the linux kernel to do the early setup. I think we are in the code section where we spin loop the secondaries. Most of the time is spent in skiboot under cpu_idle/relax. Any idea where that could come from ? > See c22edfebff29f63d793032e4fbd42a035bb73e27 for an example. Thanks for the hint. C.
