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[Qemu-devel] [PULL 51/60] kvm: support -overcommit cpu-pm=on|off
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 51/60] kvm: support -overcommit cpu-pm=on|off |
Date: |
Thu, 28 Jun 2018 22:05:01 +0200 |
From: "Michael S. Tsirkin" <address@hidden>
With this flag, kvm allows guest to control host CPU power state. This
increases latency for other processes using same host CPU in an
unpredictable way, but if decreases idle entry/exit times for the
running VCPU, so to use it QEMU needs a hint about whether host CPU is
overcommitted, hence the flag name.
Follow-up patches will expose this capability to guest
(using mwait leaf).
Based on a patch by Wanpeng Li <address@hidden> .
Signed-off-by: Michael S. Tsirkin <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
include/sysemu/sysemu.h | 1 +
qemu-options.hx | 24 ++++++++++++++++++++++++
target/i386/kvm.c | 23 +++++++++++++++++++++++
vl.c | 32 +++++++++++++++++++++++++++++++-
4 files changed, 79 insertions(+), 1 deletion(-)
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index e893f72..b921c6f 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -128,6 +128,7 @@ extern bool boot_strict;
extern uint8_t *boot_splash_filedata;
extern size_t boot_splash_filedata_size;
extern bool enable_mlock;
+extern bool enable_cpu_pm;
extern uint8_t qemu_extra_params_fw[2];
extern QEMUClockType rtc_clock;
extern const char *mem_path;
diff --git a/qemu-options.hx b/qemu-options.hx
index 3e45483..81b1e99 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3325,6 +3325,30 @@ mlocking qemu and guest memory can be enabled via
@option{mlock=on}
(enabled by default).
ETEXI
+DEF("overcommit", HAS_ARG, QEMU_OPTION_overcommit,
+ "--overcommit [mem-lock=on|off][cpu-pm=on|off]\n"
+ " run qemu with overcommit hints\n"
+ " mem-lock=on|off controls memory lock support (default:
off)\n"
+ " cpu-pm=on|off controls cpu power management (default:
off)\n",
+ QEMU_ARCH_ALL)
+STEXI
address@hidden -overcommit mem-lock=on|off
address@hidden -overcommit cpu-pm=on|off
address@hidden -overcommit
+Run qemu with hints about host resource overcommit. The default is
+to assume that host overcommits all resources.
+
+Locking qemu and guest memory can be enabled via @option{mem-lock=on} (disabled
+by default). This works when host memory is not overcommitted and reduces the
+worst-case latency for guest. This is equivalent to @option{realtime}.
+
+Guest ability to manage power state of host cpus (increasing latency for other
+processes on the same host cpu, but decreasing latency for guest) can be
+enabled via @option{cpu-pm=on} (disabled by default). This works best when
+host CPU is not overcommitted. When used, host estimates of CPU cycle and power
+utilization will be incorrect, not taking into account guest idle time.
+ETEXI
+
DEF("gdb", HAS_ARG, QEMU_OPTION_gdb, \
"-gdb dev wait for gdb connection on 'dev'\n", QEMU_ARCH_ALL)
STEXI
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 2d174f3..dc991f6 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -1387,6 +1387,29 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
smram_machine_done.notify = register_smram_listener;
qemu_add_machine_init_done_notifier(&smram_machine_done);
}
+
+ if (enable_cpu_pm) {
+ int disable_exits = kvm_check_extension(s, KVM_CAP_X86_DISABLE_EXITS);
+ int ret;
+
+/* Work around for kernel header with a typo. TODO: fix header and drop. */
+#if defined(KVM_X86_DISABLE_EXITS_HTL) && !defined(KVM_X86_DISABLE_EXITS_HLT)
+#define KVM_X86_DISABLE_EXITS_HLT KVM_X86_DISABLE_EXITS_HTL
+#endif
+ if (disable_exits) {
+ disable_exits &= (KVM_X86_DISABLE_EXITS_MWAIT |
+ KVM_X86_DISABLE_EXITS_HLT |
+ KVM_X86_DISABLE_EXITS_PAUSE);
+ }
+
+ ret = kvm_vm_enable_cap(s, KVM_CAP_X86_DISABLE_EXITS, 0,
+ disable_exits);
+ if (ret < 0) {
+ error_report("kvm: guest stopping CPU not supported: %s",
+ strerror(-ret));
+ }
+ }
+
return 0;
}
diff --git a/vl.c b/vl.c
index 7c9f19a..ef6cfce 100644
--- a/vl.c
+++ b/vl.c
@@ -142,6 +142,7 @@ ram_addr_t ram_size;
const char *mem_path = NULL;
int mem_prealloc = 0; /* force preallocation of physical target memory */
bool enable_mlock = false;
+bool enable_cpu_pm = false;
int nb_nics;
NICInfo nd_table[MAX_NICS];
int autostart;
@@ -390,6 +391,22 @@ static QemuOptsList qemu_realtime_opts = {
},
};
+static QemuOptsList qemu_overcommit_opts = {
+ .name = "overcommit",
+ .head = QTAILQ_HEAD_INITIALIZER(qemu_overcommit_opts.head),
+ .desc = {
+ {
+ .name = "mem-lock",
+ .type = QEMU_OPT_BOOL,
+ },
+ {
+ .name = "cpu-pm",
+ .type = QEMU_OPT_BOOL,
+ },
+ { /* end of list */ }
+ },
+};
+
static QemuOptsList qemu_msg_opts = {
.name = "msg",
.head = QTAILQ_HEAD_INITIALIZER(qemu_msg_opts.head),
@@ -3906,7 +3923,20 @@ int main(int argc, char **argv, char **envp)
if (!opts) {
exit(1);
}
- enable_mlock = qemu_opt_get_bool(opts, "mlock", true);
+ /* Don't override the -overcommit option if set */
+ enable_mlock = enable_mlock ||
+ qemu_opt_get_bool(opts, "mlock", true);
+ break;
+ case QEMU_OPTION_overcommit:
+ opts = qemu_opts_parse_noisily(qemu_find_opts("overcommit"),
+ optarg, false);
+ if (!opts) {
+ exit(1);
+ }
+ /* Don't override the -realtime option if set */
+ enable_mlock = enable_mlock ||
+ qemu_opt_get_bool(opts, "mem-lock", false);
+ enable_cpu_pm = qemu_opt_get_bool(opts, "cpu-pm", false);
break;
case QEMU_OPTION_msg:
opts = qemu_opts_parse_noisily(qemu_find_opts("msg"), optarg,
--
1.8.3.1
- [Qemu-devel] [PULL 37/60] pr-manager-helper: report event on connection/disconnection, (continued)
- [Qemu-devel] [PULL 37/60] pr-manager-helper: report event on connection/disconnection, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 41/60] WHPX: register for unrecognized MSR exits, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 43/60] target-i386: Add NMI interception to SVM, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 42/60] memory/hmp: Print owners/parents in "info mtree", Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 48/60] ioapic: some proper indents when dump info, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 46/60] doc: another fix to "info pic", Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 44/60] target-i386: Allow interrupt injection after STGI, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 45/60] target-i386: Mark cpu_vmexit noreturn, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 47/60] ioapic: support "info pic", Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 49/60] ioapic: support "info irq", Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 51/60] kvm: support -overcommit cpu-pm=on|off,
Paolo Bonzini <=
- [Qemu-devel] [PULL 52/60] i386/cpu: make -cpu host support monitor/mwait, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 54/60] dump: use system context in Windows dump, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 56/60] dump: add Windows live system dump, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 53/60] dump: add Windows dump format to dump-guest-memory, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 55/60] dump: add fallback KDBG using in Windows dump, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 50/60] hmp: obsolete "info ioapic", Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 58/60] hw/scsi: centralize SG_IO calls into single function, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 60/60] tests/boot-serial: Do not delete the output file in case of errors, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 59/60] hw/scsi: add VPD Block Limits emulation, Paolo Bonzini, 2018/06/28
- [Qemu-devel] [PULL 57/60] hw/scsi: cleanups before VPD BL emulation, Paolo Bonzini, 2018/06/28