KVM: ppc: Implement in-kernel exit timing statistics
Existing KVM statistics are either just counters (kvm_stat) reported for
KVM generally or trace based aproaches like kvm_trace.
For KVM on powerpc we had the need to track the timings of the different exit
types. While this could be achieved parsing data created with a kvm_trace
extension this adds too much overhead (at least on embedded PowerPC) slowing
down the workloads we wanted to measure.
Therefore this patch adds a in-kernel exit timing statistic to the powerpc kvm
code. These statistic is available per vm&vcpu under the kvm debugfs directory.
As this statistic is low, but still some overhead it can be enabled via a
.config entry and should be off by default.
Since this patch touched all powerpc kvm_stat code anyway this code is now
merged and simplified together with the exit timing statistic code (still
working with exit timing disabled in .config).
Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/powerpc/kvm/timing.c b/arch/powerpc/kvm/timing.c
new file mode 100644
index 0000000..f42d272
--- /dev/null
+++ b/arch/powerpc/kvm/timing.c
@@ -0,0 +1,262 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * Copyright IBM Corp. 2007
+ *
+ * Authors: Hollis Blanchard <hollisb@us.ibm.com>
+ * Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/fs.h>
+#include <linux/seq_file.h>
+#include <linux/debugfs.h>
+#include <linux/uaccess.h>
+
+#include "timing.h"
+#include <asm/time.h>
+#include <asm-generic/div64.h>
+
+void kvmppc_init_timing_stats(struct kvm_vcpu *vcpu)
+{
+ int i;
+
+ /* pause guest execution to avoid concurrent updates */
+ local_irq_disable();
+ mutex_lock(&vcpu->mutex);
+
+ vcpu->arch.last_exit_type = 0xDEAD;
+ for (i = 0; i < __NUMBER_OF_KVM_EXIT_TYPES; i++) {
+ vcpu->arch.timing_count_type[i] = 0;
+ vcpu->arch.timing_max_duration[i] = 0;
+ vcpu->arch.timing_min_duration[i] = 0xFFFFFFFF;
+ vcpu->arch.timing_sum_duration[i] = 0;
+ vcpu->arch.timing_sum_quad_duration[i] = 0;
+ }
+ vcpu->arch.timing_last_exit = 0;
+ vcpu->arch.timing_exit.tv64 = 0;
+ vcpu->arch.timing_last_enter.tv64 = 0;
+
+ mutex_unlock(&vcpu->mutex);
+ local_irq_enable();
+}
+
+static void add_exit_timing(struct kvm_vcpu *vcpu,
+ u64 duration, int type)
+{
+ u64 old;
+
+ do_div(duration, tb_ticks_per_usec);
+ if (unlikely(duration > 0xFFFFFFFF)) {
+ printk(KERN_ERR"%s - duration too big -> overflow"
+ " duration %lld type %d exit #%d\n",
+ __func__, duration, type,
+ vcpu->arch.timing_count_type[type]);
+ return;
+ }
+
+ vcpu->arch.timing_count_type[type]++;
+
+ /* sum */
+ old = vcpu->arch.timing_sum_duration[type];
+ vcpu->arch.timing_sum_duration[type] += duration;
+ if (unlikely(old > vcpu->arch.timing_sum_duration[type])) {
+ printk(KERN_ERR"%s - wrap adding sum of durations"
+ " old %lld new %lld type %d exit # of type %d\n",
+ __func__, old, vcpu->arch.timing_sum_duration[type],
+ type, vcpu->arch.timing_count_type[type]);
+ }
+
+ /* square sum */
+ old = vcpu->arch.timing_sum_quad_duration[type];
+ vcpu->arch.timing_sum_quad_duration[type] += (duration*duration);
+ if (unlikely(old > vcpu->arch.timing_sum_quad_duration[type])) {
+ printk(KERN_ERR"%s - wrap adding sum of squared durations"
+ " old %lld new %lld type %d exit # of type %d\n",
+ __func__, old,
+ vcpu->arch.timing_sum_quad_duration[type],
+ type, vcpu->arch.timing_count_type[type]);
+ }
+
+ /* set min/max */
+ if (unlikely(duration < vcpu->arch.timing_min_duration[type]))
+ vcpu->arch.timing_min_duration[type] = duration;
+ if (unlikely(duration > vcpu->arch.timing_max_duration[type]))
+ vcpu->arch.timing_max_duration[type] = duration;
+}
+
+void kvmppc_update_timing_stats(struct kvm_vcpu *vcpu)
+{
+ u64 exit = vcpu->arch.timing_last_exit;
+ u64 enter = vcpu->arch.timing_last_enter.tv64;
+
+ /* save exit time, used next exit when the reenter time is known */
+ vcpu->arch.timing_last_exit = vcpu->arch.timing_exit.tv64;
+
+ if (unlikely(vcpu->arch.last_exit_type == 0xDEAD || exit == 0))
+ return; /* skip incomplete cycle (e.g. after reset) */
+
+ /* update statistics for average and standard deviation */
+ add_exit_timing(vcpu, (enter - exit), vcpu->arch.last_exit_type);
+ /* enter -> timing_last_exit is time spent in guest - log this too */
+ add_exit_timing(vcpu, (vcpu->arch.timing_last_exit - enter),
+ TIMEINGUEST);
+}
+
+static const char *kvm_exit_names[__NUMBER_OF_KVM_EXIT_TYPES] = {
+ [MMIO_EXITS] = "MMIO",
+ [DCR_EXITS] = "DCR",
+ [SIGNAL_EXITS] = "SIGNAL",
+ [ITLB_REAL_MISS_EXITS] = "ITLBREAL",
+ [ITLB_VIRT_MISS_EXITS] = "ITLBVIRT",
+ [DTLB_REAL_MISS_EXITS] = "DTLBREAL",
+ [DTLB_VIRT_MISS_EXITS] = "DTLBVIRT",
+ [SYSCALL_EXITS] = "SYSCALL",
+ [ISI_EXITS] = "ISI",
+ [DSI_EXITS] = "DSI",
+ [EMULATED_INST_EXITS] = "EMULINST",
+ [EMULATED_MTMSRWE_EXITS] = "EMUL_WAIT",
+ [EMULATED_WRTEE_EXITS] = "EMUL_WRTEE",
+ [EMULATED_MTSPR_EXITS] = "EMUL_MTSPR",
+ [EMULATED_MFSPR_EXITS] = "EMUL_MFSPR",
+ [EMULATED_MTMSR_EXITS] = "EMUL_MTMSR",
+ [EMULATED_MFMSR_EXITS] = "EMUL_MFMSR",
+ [EMULATED_TLBSX_EXITS] = "EMUL_TLBSX",
+ [EMULATED_TLBWE_EXITS] = "EMUL_TLBWE",
+ [EMULATED_RFI_EXITS] = "EMUL_RFI",
+ [DEC_EXITS] = "DEC",
+ [EXT_INTR_EXITS] = "EXTINT",
+ [HALT_WAKEUP] = "HALT",
+ [USR_PR_INST] = "USR_PR_INST",
+ [FP_UNAVAIL] = "FP_UNAVAIL",
+ [DEBUG_EXITS] = "DEBUG",
+ [TIMEINGUEST] = "TIMEINGUEST"
+};
+
+static int kvmppc_exit_timing_show(struct seq_file *m, void *private)
+{
+ struct kvm_vcpu *vcpu = m->private;
+ int i;
+ u64 min, max;
+
+ for (i = 0; i < __NUMBER_OF_KVM_EXIT_TYPES; i++) {
+ if (vcpu->arch.timing_min_duration[i] == 0xFFFFFFFF)
+ min = 0;
+ else
+ min = vcpu->arch.timing_min_duration[i];
+ if (vcpu->arch.timing_max_duration[i] == 0)
+ max = 0;
+ else
+ max = vcpu->arch.timing_max_duration[i];
+
+ seq_printf(m, "%12s: count %10d min %10lld "
+ "max %10lld sum %20lld sum_quad %20lld\n",
+ kvm_exit_names[i], vcpu->arch.timing_count_type[i],
+ vcpu->arch.timing_min_duration[i],
+ vcpu->arch.timing_max_duration[i],
+ vcpu->arch.timing_sum_duration[i],
+ vcpu->arch.timing_sum_quad_duration[i]);
+ }
+ return 0;
+}
+
+static ssize_t kvmppc_exit_timing_write(struct file *file,
+ const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ size_t len;
+ int err;
+ const char __user *p;
+ char c;
+
+ len = 0;
+ p = user_buf;
+ while (len < count) {
+ if (get_user(c, p++))
+ err = -EFAULT;
+ if (c == 0 || c == '\n')
+ break;
+ len++;
+ }
+
+ if (len > 1) {
+ err = -EINVAL;
+ goto done;
+ }
+
+ if (copy_from_user(&c, user_buf, sizeof(c))) {
+ err = -EFAULT;
+ goto done;
+ }
+
+ if (c == 'c') {
+ struct seq_file *seqf = (struct seq_file *)file->private_data;
+ struct kvm_vcpu *vcpu = seqf->private;
+ /* write does not affect out buffers previsously generated with
+ * show. Seq file is locked here to prevent races of init with
+ * a show call */
+ mutex_lock(&seqf->lock);
+ kvmppc_init_timing_stats(vcpu);
+ mutex_unlock(&seqf->lock);
+ err = count;
+ } else {
+ err = -EINVAL;
+ goto done;
+ }
+
+done:
+ return err;
+}
+
+static int kvmppc_exit_timing_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, kvmppc_exit_timing_show, inode->i_private);
+}
+
+static struct file_operations kvmppc_exit_timing_fops = {
+ .owner = THIS_MODULE,
+ .open = kvmppc_exit_timing_open,
+ .read = seq_read,
+ .write = kvmppc_exit_timing_write,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+void kvmppc_create_vcpu_debugfs(struct kvm_vcpu *vcpu, unsigned int id)
+{
+ static char dbg_fname[50];
+ struct dentry *debugfs_file;
+
+ snprintf(dbg_fname, sizeof(dbg_fname), "vm%u_vcpu%03u_timing",
+ current->pid, id);
+ debugfs_file = debugfs_create_file(dbg_fname, 0666,
+ kvm_debugfs_dir, vcpu,
+ &kvmppc_exit_timing_fops);
+
+ if (!debugfs_file) {
+ printk(KERN_ERR"%s: error creating debugfs file %s\n",
+ __func__, dbg_fname);
+ return;
+ }
+
+ vcpu->arch.debugfs_exit_timing = debugfs_file;
+}
+
+void kvmppc_remove_vcpu_debugfs(struct kvm_vcpu *vcpu)
+{
+ if (vcpu->arch.debugfs_exit_timing) {
+ debugfs_remove(vcpu->arch.debugfs_exit_timing);
+ vcpu->arch.debugfs_exit_timing = NULL;
+ }
+}