On Thu, Jul 22, 2010 at 9:48 AM, Chen Yufei <cyfde...@gmail.com> wrote: > On 2010-7-22, at 上午1:04, Stefan Weil wrote: > >> Am 21.07.2010 09:03, schrieb Chen Yufei: >>> On 2010-7-21, at 上午5:43, Blue Swirl wrote: >>> >>> >>>> On Sat, Jul 17, 2010 at 10:27 AM, Chen Yufei<cyfde...@gmail.com> wrote: >>>> >>>>> We are pleased to announce COREMU, which is a "multicore-on-multicore" >>>>> full-system emulator built on Qemu. (Simply speaking, we made Qemu >>>>> parallel.) >>>>> >>>>> The project web page is located at: >>>>> http://ppi.fudan.edu.cn/coremu >>>>> >>>>> You can also download the source code, images for playing on sourceforge >>>>> http://sf.net/p/coremu >>>>> >>>>> COREMU is composed of >>>>> 1. a parallel emulation library >>>>> 2. a set of patches to qemu >>>>> (We worked on the master branch, commit >>>>> 54d7cf136f040713095cbc064f62d753bff6f9d2) >>>>> >>>>> It currently supports full-system emulation of x64 and ARM MPcore >>>>> platforms. >>>>> >>>>> By leveraging the underlying multicore resources, it can emulate up to >>>>> 255 cores running commodity operating systems (even on a 4-core machine). >>>>> >>>>> Enjoy, >>>>> >>>> Nice work. Do you plan to submit the improvements back to upstream QEMU? >>>> >>> It would be great if we can submit our code to QEMU, but we do not know the >>> process. >>> Would you please give us some instructions? >>> >>> -- >>> Best regards, >>> Chen Yufei >>> >> >> Some hints can be found here: >> http://wiki.qemu.org/Contribute/StartHere >> >> Kind regards, >> Stefan Weil > > The patch is in the attachment, produced with command > git diff 54d7cf136f040713095cbc064f62d753bff6f9d2 > > In order to separate what need to be done to make QEMU parallel, we created a > separate library, and the patched QEMU need to be compiled and linked with > that library. To submit our enhancement to QEMU, maybe we need to incorporate > this library into QEMU. I don't know what would be the best solution. > > Our approach to make QEMU parallel can be found at > http://ppi.fudan.edu.cn/coremu > > I will give a short summary here: > > 1. Each emulated core thread runs a separate binary translator engine and has > private code cache. We marked some variables in TCG as thread local. We also > modified the TB invalidation mechanism. > > 2. Each core has a queue holding pending interrupts. The COREMU library > provides this queue, and interrupt notification is done by sending realtime > signals to the emulated core thread. > > 3. Atomic instruction emulation has to be modified for parallel emulation. We > use lightweight memory transaction which requires only compare-and-swap > instruction to emulate atomic instruction. > > 4. Some code in the original QEMU may cause data race bug after we make it > parallel. We fixed these problems. > > > > > -- > Best regards, > Chen Yufei
Looking at the patch it seems there is a global lock for hardware access via coremu_spin_lock(&cm_hw_lock). How many cores have you tried running and do you have lock contention data for cm_hw_lock? Have you thought about making hardware emulation concurrent? These are issues that qemu-kvm faces today since it executes vcpu threads in parallel. Both qemu-kvm and the COREMU patches could benefit from a solution for concurrent hardware access. Stefan
