[v7] tcg: CPUTLBEntryFull and TARGET_TB_PCREL

[PATCH v7 01/18] cpu: cache CPUClass in CPUState for hot code paths

Richard Henderson posted 18 patches 3 years, 4 months ago

Diff against v5 v6
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Maintainers: Richard Henderson <richard.henderson@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, Eduardo Habkost <eduardo@habkost.net>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, "Philippe Mathieu-Daudé" <f4bug@amsat.org>, Yanan Wang <wangyanan55@huawei.com>, "Alex Bennée" <alex.bennee@linaro.org>, Alexandre Iooss <erdnaxe@crans.org>, Mahmoud Mandour <ma.mandourr@gmail.com>, Peter Maydell <peter.maydell@linaro.org>, Michael Rolnik <mrolnik@gmail.com>, "Edgar E. Iglesias" <edgar.iglesias@gmail.com>, Taylor Simpson <tsimpson@quicinc.com>, Song Gao <gaosong@loongson.cn>, Xiaojuan Yang <yangxiaojuan@loongson.cn>, Laurent Vivier <laurent@vivier.eu>, Aurelien Jarno <aurelien@aurel32.net>, Jiaxun Yang <jiaxun.yang@flygoat.com>, Aleksandar Rikalo <aleksandar.rikalo@syrmia.com>, Chris Wulff <crwulff@gmail.com>, Marek Vasut <marex@denx.de>, Stafford Horne <shorne@gmail.com>, "Cédric Le Goater" <clg@kaod.org>, Daniel Henrique Barboza <danielhb413@gmail.com>, David Gibson <david@gibson.dropbear.id.au>, Greg Kurz <groug@kaod.org>, Palmer Dabbelt <palmer@dabbelt.com>, Alistair Francis <alistair.francis@wdc.com>, Bin Meng <bin.meng@windriver.com>, Yoshinori Sato <ysato@users.sourceforge.jp>, Cornelia Huck <cohuck@redhat.com>, Thomas Huth <thuth@redhat.com>, David Hildenbrand <david@redhat.com>, Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>, Artyom Tarasenko <atar4qemu@gmail.com>, Bastian Koppelmann <kbastian@mail.uni-paderborn.de>, Max Filippov <jcmvbkbc@gmail.com>, Stefan Hajnoczi <stefanha@redhat.com>

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[PATCH v7 01/18] cpu: cache CPUClass in CPUState for hot code paths

Posted by Richard Henderson 3 years, 4 months ago

From: Alex Bennée <alex.bennee@linaro.org>

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 <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220811151413.3350684-3-alex.bennee@linaro.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20220923084803.498337-3-clg@kaod.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/hw/core/cpu.h | 9 +++++++++
 cpu.c                 | 9 ++++-----
 2 files changed, 13 insertions(+), 5 deletions(-)

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;
diff --git a/cpu.c b/cpu.c
index 584ac78baf..14365e36f3 100644
--- a/cpu.c
+++ b/cpu.c
@@ -131,9 +131,8 @@ const VMStateDescription vmstate_cpu_common = {
 
 void cpu_exec_realizefn(CPUState *cpu, Error **errp)
 {
-#ifndef CONFIG_USER_ONLY
-    CPUClass *cc = CPU_GET_CLASS(cpu);
-#endif
+    /* cache the cpu class for the hotpath */
+    cpu->cc = CPU_GET_CLASS(cpu);
 
     cpu_list_add(cpu);
     if (!accel_cpu_realizefn(cpu, errp)) {
@@ -151,8 +150,8 @@ void cpu_exec_realizefn(CPUState *cpu, Error **errp)
     if (qdev_get_vmsd(DEVICE(cpu)) == NULL) {
         vmstate_register(NULL, cpu->cpu_index, &vmstate_cpu_common, cpu);
     }
-    if (cc->sysemu_ops->legacy_vmsd != NULL) {
-        vmstate_register(NULL, cpu->cpu_index, cc->sysemu_ops->legacy_vmsd, cpu);
+    if (cpu->cc->sysemu_ops->legacy_vmsd != NULL) {
+        vmstate_register(NULL, cpu->cpu_index, cpu->cc->sysemu_ops->legacy_vmsd, cpu);
     }
 #endif /* CONFIG_USER_ONLY */
 }
-- 
2.34.1