Set pv_time_ops.sched_clock to vmware_sched_clock(). It is simplified
version of native_sched_clock() without ring buffer of mult/shift/offset
triplets and preempt toggling.
Since VMware hypervisor provides constant tsc we can use constant
mult/shift/offset triplet calculated at boot time.
no-vmw-sched-clock kernel parameter is added to switch back to the
native_sched_clock() implementation.
Signed-off-by: Alexey Makhalov <amakhalov@xxxxxxxxxx>
Acked-by: Alok N Kataria <akataria@xxxxxxxxxx>
---
Documentation/kernel-parameters.txt | 4 ++++
arch/x86/kernel/cpu/vmware.c | 38 +++++++++++++++++++++++++++++++++++++
2 files changed, 42 insertions(+)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 37babf9..b3b2ec0 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2754,6 +2754,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
fault handling.
+ no-vmw-sched-clock
+ [X86,PV_OPS] Disable paravirtualized VMware scheduler
+ clock and use the default one.
+
no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
steal time is computed, but won't influence scheduler
behaviour
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index e3fb320..6ef22c1 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -24,10 +24,12 @@
#include <linux/dmi.h>
#include <linux/init.h>
#include <linux/export.h>
+#include <linux/clocksource.h>
#include <asm/div64.h>
#include <asm/x86_init.h>
#include <asm/hypervisor.h>
#include <asm/apic.h>
+#include <asm/timer.h>
#define CPUID_VMWARE_INFO_LEAF 0x40000000
#define VMWARE_HYPERVISOR_MAGIC 0x564D5868
@@ -62,10 +64,46 @@ static unsigned long vmware_get_tsc_khz(void)
}
#ifdef CONFIG_PARAVIRT
+static struct cyc2ns_data vmware_cyc2ns __ro_after_init;
+
+static int vmw_sched_clock __initdata = 1;
+static __init int setup_vmw_sched_clock(char *s)
+{
+ vmw_sched_clock = 0;
+ return 0;
+}
+early_param("no-vmw-sched-clock", setup_vmw_sched_clock);
+
+static unsigned long long vmware_sched_clock(void)
+{
+ unsigned long long ns;
+
+ ns = mul_u64_u32_shr(rdtsc(), vmware_cyc2ns.cyc2ns_mul,
+ vmware_cyc2ns.cyc2ns_shift);
+ ns -= vmware_cyc2ns.cyc2ns_offset;
+ return ns;
+}
+
static void __init vmware_paravirt_ops_setup(void)
{
pv_info.name = "VMware";
pv_cpu_ops.io_delay = paravirt_nop;
+
+ if (vmware_tsc_khz && vmw_sched_clock) {
+ unsigned long long tsc_now = rdtsc();
+
+ clocks_calc_mult_shift(&vmware_cyc2ns.cyc2ns_mul,
+ &vmware_cyc2ns.cyc2ns_shift,
+ vmware_tsc_khz,
+ NSEC_PER_MSEC, 0);
+ vmware_cyc2ns.cyc2ns_offset =
+ mul_u64_u32_shr(tsc_now, vmware_cyc2ns.cyc2ns_mul,
+ vmware_cyc2ns.cyc2ns_shift);
+
+ pv_time_ops.sched_clock = vmware_sched_clock;
+ pr_info("vmware: using sched offset of %llu ns\n",
+ vmware_cyc2ns.cyc2ns_offset);
+ }
}
#else
#define vmware_paravirt_ops_setup() do {} while (0)
--
2.10.1
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