From: tip-bot for Alexey Makhalov <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, tglx@linutronix.de,
mingo@kernel.org, akataria@vmware.com, amakhalov@vmware.com
Subject: [tip:x86/platform] x86/vmware: Add paravirt sched clock
Date: Sun, 30 Oct 2016 18:18:23 -0700 [thread overview]
Message-ID: <tip-80e9a4f21fd7ccce7e9b8439986fd028c9946dda@git.kernel.org> (raw)
In-Reply-To: <20161028075432.90579-4-amakhalov@vmware.com>
Commit-ID: 80e9a4f21fd7ccce7e9b8439986fd028c9946dda
Gitweb: http://git.kernel.org/tip/80e9a4f21fd7ccce7e9b8439986fd028c9946dda
Author: Alexey Makhalov <amakhalov@vmware.com>
AuthorDate: Fri, 28 Oct 2016 00:54:32 -0700
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 30 Oct 2016 08:57:08 +0100
x86/vmware: Add paravirt sched clock
The default sched_clock() implementation is native_sched_clock(). It
contains code to handle non constant frequency TSCs, which creates
overhead for systems with constant frequency TSCs.
The vmware hypervisor guarantees a constant frequency TSC, so
native_sched_clock() is not required and slower than a dedicated function
which operates with one time calculated conversion factors.
Calculate the conversion factors at boot time from the tsc frequency and
install an optimized sched_clock() function via paravirt ops.
The paravirtualized clock can be disabled on the kernel command line with
the new 'no-vmw-sched-clock' option.
Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
Cc: linux-doc@vger.kernel.org
Cc: pv-drivers@vmware.com
Cc: corbet@lwn.net
Cc: virtualization@lists.linux-foundation.org
Link: http://lkml.kernel.org/r/20161028075432.90579-4-amakhalov@vmware.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
Documentation/kernel-parameters.txt | 4 ++++
arch/x86/kernel/cpu/vmware.c | 42 +++++++++++++++++++++++++++++++++++++
2 files changed, 46 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 098a524..cdbe38b 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -24,10 +24,15 @@
#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>
+
+#undef pr_fmt
+#define pr_fmt(fmt) "vmware: " fmt
#define CPUID_VMWARE_INFO_LEAF 0x40000000
#define VMWARE_HYPERVISOR_MAGIC 0x564D5868
@@ -62,10 +67,47 @@ 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_sched_clock_setup(void)
+{
+ struct cyc2ns_data *d = &vmware_cyc2ns;
+ unsigned long long tsc_now = rdtsc();
+
+ clocks_calc_mult_shift(&d->cyc2ns_mul, &d->cyc2ns_shift,
+ vmware_tsc_khz, NSEC_PER_MSEC, 0);
+ d->cyc2ns_offset = mul_u64_u32_shr(tsc_now, d->cyc2ns_mul,
+ d->cyc2ns_shift);
+
+ pv_time_ops.sched_clock = vmware_sched_clock;
+ pr_info("using sched offset of %llu ns\n", d->cyc2ns_offset);
+}
+
static void __init vmware_paravirt_ops_setup(void)
{
pv_info.name = "VMware hypervisor";
pv_cpu_ops.io_delay = paravirt_nop;
+
+ if (vmware_tsc_khz && vmw_sched_clock)
+ vmware_sched_clock_setup();
}
#else
#define vmware_paravirt_ops_setup() do {} while (0)
next prev parent reply other threads:[~2016-10-31 1:18 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-26 5:20 [PATCH 0/3] x86/vmware guest improvements Alexey Makhalov
2016-10-26 5:20 ` [PATCH 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu() Alexey Makhalov
2016-10-26 5:26 ` [PATCH 2/3] x86/vmware: Add basic paravirt ops support Alexey Makhalov
2016-10-26 20:47 ` Tim Mann
2016-10-26 20:47 ` Thomas Gleixner
2016-10-27 19:44 ` [RESEND PATCH 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu() Alexey Makhalov
2016-10-27 19:44 ` [RESEND PATCH 2/3] x86/vmware: Add basic paravirt ops support Alexey Makhalov
2016-10-27 19:44 ` [RESEND PATCH 3/3] x86/vmware: Add paravirt sched clock Alexey Makhalov
2016-10-27 22:10 ` Thomas Gleixner
2016-10-27 21:44 ` [RESEND PATCH 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu() Thomas Gleixner
2016-10-28 7:54 ` [PATCH v3 0/3] x86/vmware guest improvements Alexey Makhalov
2016-10-28 7:54 ` [PATCH v3 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu() Alexey Makhalov
2016-10-31 1:17 ` [tip:x86/platform] " tip-bot for Alexey Makhalov
2016-10-28 7:54 ` [PATCH v3 2/3] x86/vmware: Add basic paravirt ops support Alexey Makhalov
2016-10-31 1:17 ` [tip:x86/platform] " tip-bot for Alexey Makhalov
2016-10-28 7:54 ` [PATCH v3 3/3] x86/vmware: Add paravirt sched clock Alexey Makhalov
2016-10-31 1:18 ` tip-bot for Alexey Makhalov [this message]
2016-10-26 5:26 ` [PATCH " Alexey Makhalov
2016-10-26 10:18 ` Thomas Gleixner
2016-10-26 16:51 ` [PATCH v2 " Alexey Makhalov
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