From 6fbdff870620705042a5b2d87491659487b3f4e2 Mon Sep 17 00:00:00 2001 From: Alex Bennée Date: Fri, 23 Sep 2022 10:47:59 +0200 Subject: cpu: cache CPUClass in CPUState for hot code paths The class cast checkers are quite expensive and always on (unlike the dynamic case who's checks are gated by CONFIG_QOM_CAST_DEBUG). To avoid the overhead of repeatedly checking something which should never change we cache the CPUClass reference for use in the hot code paths. Signed-off-by: Alex Bennée Reviewed-by: Richard Henderson Message-Id: <20220811151413.3350684-3-alex.bennee@linaro.org> Signed-off-by: Cédric Le Goater Message-Id: <20220923084803.498337-3-clg@kaod.org> Signed-off-by: Richard Henderson --- include/hw/core/cpu.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/hw') diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h index 500503da13..1a7e1a9380 100644 --- a/include/hw/core/cpu.h +++ b/include/hw/core/cpu.h @@ -51,6 +51,13 @@ typedef int (*WriteCoreDumpFunction)(const void *buf, size_t size, */ #define CPU(obj) ((CPUState *)(obj)) +/* + * The class checkers bring in CPU_GET_CLASS() which is potentially + * expensive given the eventual call to + * object_class_dynamic_cast_assert(). Because of this the CPUState + * has a cached value for the class in cs->cc which is set up in + * cpu_exec_realizefn() for use in hot code paths. + */ typedef struct CPUClass CPUClass; DECLARE_CLASS_CHECKERS(CPUClass, CPU, TYPE_CPU) @@ -317,6 +324,8 @@ struct qemu_work_item; struct CPUState { /*< private >*/ DeviceState parent_obj; + /* cache to avoid expensive CPU_GET_CLASS */ + CPUClass *cc; /*< public >*/ int nr_cores; -- cgit v1.2.3-55-g7522