From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39578) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZOozF-00065U-3T for qemu-devel@nongnu.org; Mon, 10 Aug 2015 11:27:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZOozB-00086y-Kl for qemu-devel@nongnu.org; Mon, 10 Aug 2015 11:27:41 -0400 Received: from greensocs.com ([193.104.36.180]:59089) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZOozB-00086T-9t for qemu-devel@nongnu.org; Mon, 10 Aug 2015 11:27:37 -0400 From: fred.konrad@greensocs.com Date: Mon, 10 Aug 2015 17:26:58 +0200 Message-Id: <1439220437-23957-1-git-send-email-fred.konrad@greensocs.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [RFC PATCH V7 00/19] Multithread TCG. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, mttcg@listserver.greensocs.com Cc: mark.burton@greensocs.com, a.rigo@virtualopensystems.com, guillaume.delbergue@greensocs.com, pbonzini@redhat.com, alex.bennee@linaro.org, fred.konrad@greensocs.com From: KONRAD Frederic This is the 7th round of the MTTCG patch series. It can be cloned from: git@git.greensocs.com:fkonrad/mttcg.git branch multi_tcg_v7. This patch-set try to address the different issues in the global picture = of MTTCG, presented on the wiki. =3D=3D Needed patch for our work =3D=3D Some preliminaries are needed for our work: * current_cpu doesn't make sense in mttcg so a tcg_executing flag is add= ed to the CPUState. * We need to run some work safely when all VCPUs are outside their execu= tion loop. This is done with the async_run_safe_work_on_cpu function introd= uced in this series. * QemuSpin lock is introduced (on posix only yet) to allow a faster hand= ling of atomic instruction. =3D=3D Code generation and cache =3D=3D As Qemu stands, there is no protection at all against two threads attempt= ing to generate code at the same time or modifying a TranslationBlock. The "protect TBContext with tb_lock" patch address the issue of code gene= ration and makes all the tb_* function thread safe (except tb_flush). This raised the question of one or multiple caches. We choosed to use one unified cache because it's easier as a first step and since the structure= of QEMU effectively has a =E2=80=98local=E2=80=99 cache per CPU in the form = of the jump cache, we don't see the benefit of having two pools of tbs. =3D=3D Dirty tracking =3D=3D Protecting the IOs: To allows all VCPUs threads to run at the same time we need to drop the global_mutex as soon as possible. The io access need to take the mutex. T= his is likely to change when http://thread.gmane.org/gmane.comp.emulators.qemu/3= 45258 will be upstreamed. Invalidation of TranslationBlocks: We can have all VCPUs running during an invalidation. Each VCPU is able t= o clean it's jump cache itself as it is in CPUState so that can be handled by a s= imple call to async_run_on_cpu. However tb_invalidate also writes to the TranslationBlock which is shared as we have only one pool. Hence this part of invalidate requires all VCPUs to exit before it can be= done. Hence the async_run_safe_work_on_cpu is introduced to handle this case. =3D=3D Atomic instruction =3D=3D For now only ARM on x64 is supported by using an cmpxchg instruction. Specifically the limitation of this approach is that it is harder to supp= ort 64bit ARM on a host architecture that is multi-core, but only supports 32= bit cmpxchg (we believe this could be the case for some PPC cores). For now = this case is not correctly handled. The existing atomic patch will attempt to = execute the 64 bit cmpxchg functionality in a non thread safe fashion. Our intent= ion is to provide a new multi-thread ARM atomic patch for 64bit ARM on effective= 32bit hosts. This atomic instruction part has been tested with Alexander's atomic stre= ss repo available here: https://lists.gnu.org/archive/html/qemu-devel/2015-06/msg05585.html The execution is a little slower than upstream probably because of the di= fferent VCPU fight for the mutex. Swaping arm_exclusive_lock from mutex to spin_l= ock reduce considerably the difference. =3D=3D Testing =3D=3D A simple double dhrystone test in SMP 2 with vexpress-a15 in a linux gues= t show a good performance progression: it takes basically 18s upstream to comple= te vs 10s with MTTCG. Testing image is available here: https://cloud.greensocs.com/index.php/s/CfHSLzDH5pmTkW3 Then simply: ./configure --target-list=3Darm-softmmu make -j8 ./arm-softmmu/qemu-system-arm -M vexpress-a15 -smp 2 -kernel zImage -initrd rootfs.ext2 -dtb vexpress-v2p-ca15-tc1.dtb --nographic --append "console=3DttyAMA0" login: root The dhrystone command is the last one in the history. "dhrystone 10000000 & dhrystone 10000000" The atomic spinlock benchmark from Alexander shows that atomic basically = work. Just follow the instruction here: https://lists.gnu.org/archive/html/qemu-devel/2015-06/msg05585.html =3D=3D Known issues =3D=3D * GDB stub: GDB stub is not tested right now it will probably requires some changes= to work. * deadlock on exit: When exiting QEMU Ctrl-C some VCPU's thread are not able to exit and co= ntinue execution. http://git.greensocs.com/fkonrad/mttcg/issues/1 * memory_region_rom_device_set_romd from pflash01 just crashes the TCG co= de. Strangely this happen only with "-smp 4" and 2 in the DTB. http://git.greensocs.com/fkonrad/mttcg/issues/2 Changes V6 -> V7: * global_lock: * Don't protect softmmu read/write helper as it's now done in adress_space_rw. * tcg_exec_flag: * Make the flag atomically test and set through an API. * introduce async_safe_work: * move qemu_cpu_kick_thread to avoid prototype declaration. * use the work_mutex. * async_work: * protect it with a mutex (work_mutex) against concurent access. * tb_lock: * protect tcg_malloc_internal as well. * signal the VCPU even of current_cpu is NULL. * added PSCI patch. * rebased on v2.4.0-rc0 (6169b60285fe1ff730d840a49527e721bfb30899). Changes V5 -> V6: * Introduce async_safe_work to do the tb_flush and some part of tb_inva= lidate. * Introduce QemuSpin from Guillaume which allow a faster atomic instruc= tion (6s to pass Alexander's atomic test instead of 30s before). * Don't take tb_lock before tb_find_fast. * Handle tb_flush with async_safe_work. * Handle tb_invalidate with async_work and async_safe_work. * Drop the tlb_flush_request mechanism and use async_work as well. * Fix the wrong lenght in atomic patch. * Fix the wrong return address for exception in atomic patch. Alex Benn=C3=A9e (1): target-arm/psci.c: wake up sleeping CPUs (MTTCG) Guillaume Delbergue (1): add support for spin lock on POSIX systems exclusively KONRAD Frederic (17): cpus: protect queued_work_* with work_mutex. cpus: add tcg_exec_flag. cpus: introduce async_run_safe_work_on_cpu. replace spinlock by QemuMutex. remove unused spinlock. protect TBContext with tb_lock. tcg: remove tcg_halt_cond global variable. Drop global lock during TCG code execution cpu: remove exit_request global. tcg: switch on multithread. Use atomic cmpxchg to atomically check the exclusive value in a STREX add a callback when tb_invalidate is called. cpu: introduce tlb_flush*_all. arm: use tlb_flush*_all translate-all: introduces tb_flush_safe. translate-all: (wip) use tb_flush_safe when we can't alloc more tb. mttcg: signal the associated cpu anyway. cpu-exec.c | 98 +++++++++------ cpus.c | 295 +++++++++++++++++++++++++-------------= ------ cputlb.c | 81 ++++++++++++ include/exec/exec-all.h | 8 +- include/exec/spinlock.h | 49 -------- include/qemu/thread-posix.h | 4 + include/qemu/thread-win32.h | 4 + include/qemu/thread.h | 7 ++ include/qom/cpu.h | 57 +++++++++ linux-user/main.c | 6 +- qom/cpu.c | 20 +++ target-arm/cpu.c | 21 ++++ target-arm/cpu.h | 6 + target-arm/helper.c | 58 +++------ target-arm/helper.h | 4 + target-arm/op_helper.c | 128 ++++++++++++++++++- target-arm/psci.c | 2 + target-arm/translate.c | 101 +++------------ target-i386/mem_helper.c | 16 ++- target-i386/misc_helper.c | 27 +++- tcg/i386/tcg-target.c | 8 ++ tcg/tcg.h | 14 ++- translate-all.c | 217 +++++++++++++++++++++++++++----- util/qemu-thread-posix.c | 45 +++++++ util/qemu-thread-win32.c | 30 +++++ vl.c | 6 + 26 files changed, 934 insertions(+), 378 deletions(-) delete mode 100644 include/exec/spinlock.h --=20 1.9.0