From 8d04fb55dec381bc5105cb47f29d918e579e8cbd Mon Sep 17 00:00:00 2001 From: Jan Kiszka Date: Thu, 23 Feb 2017 18:29:11 +0000 Subject: tcg: drop global lock during TCG code execution MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This finally allows TCG to benefit from the iothread introduction: Drop the global mutex while running pure TCG CPU code. Reacquire the lock when entering MMIO or PIO emulation, or when leaving the TCG loop. We have to revert a few optimization for the current TCG threading model, namely kicking the TCG thread in qemu_mutex_lock_iothread and not kicking it in qemu_cpu_kick. We also need to disable RAM block reordering until we have a more efficient locking mechanism at hand. Still, a Linux x86 UP guest and my Musicpal ARM model boot fine here. These numbers demonstrate where we gain something: 20338 jan 20 0 331m 75m 6904 R 99 0.9 0:50.95 qemu-system-arm 20337 jan 20 0 331m 75m 6904 S 20 0.9 0:26.50 qemu-system-arm The guest CPU was fully loaded, but the iothread could still run mostly independent on a second core. Without the patch we don't get beyond 32206 jan 20 0 330m 73m 7036 R 82 0.9 1:06.00 qemu-system-arm 32204 jan 20 0 330m 73m 7036 S 21 0.9 0:17.03 qemu-system-arm We don't benefit significantly, though, when the guest is not fully loading a host CPU. Signed-off-by: Jan Kiszka Message-Id: <1439220437-23957-10-git-send-email-fred.konrad@greensocs.com> [FK: Rebase, fix qemu_devices_reset deadlock, rm address_space_* mutex] Signed-off-by: KONRAD Frederic [EGC: fixed iothread lock for cpu-exec IRQ handling] Signed-off-by: Emilio G. Cota [AJB: -smp single-threaded fix, clean commit msg, BQL fixes] Signed-off-by: Alex Bennée Reviewed-by: Richard Henderson Reviewed-by: Pranith Kumar [PM: target-arm changes] Acked-by: Peter Maydell --- qom/cpu.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'qom') diff --git a/qom/cpu.c b/qom/cpu.c index ed87c50cea..58784bcbea 100644 --- a/qom/cpu.c +++ b/qom/cpu.c @@ -113,9 +113,19 @@ static void cpu_common_get_memory_mapping(CPUState *cpu, error_setg(errp, "Obtaining memory mappings is unsupported on this CPU."); } +/* Resetting the IRQ comes from across the code base so we take the + * BQL here if we need to. cpu_interrupt assumes it is held.*/ void cpu_reset_interrupt(CPUState *cpu, int mask) { + bool need_lock = !qemu_mutex_iothread_locked(); + + if (need_lock) { + qemu_mutex_lock_iothread(); + } cpu->interrupt_request &= ~mask; + if (need_lock) { + qemu_mutex_unlock_iothread(); + } } void cpu_exit(CPUState *cpu) -- cgit v1.2.1