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Subject[PATCH v2 5/5] perf/kvm: HCALL events analysis
Date
This patch adds KVM hypervisor call analysis to perf for powerpc.
- Trace hcall events :
perf kvm stat record

- Show the results :
perf kvm stat report --event=hcall

The results show the number of hypervisor calls from the guest grouped
into their respective reasons displayed with the frequency.

This patch makes use of two additional tracepoints "kvm_hv:kvm_hcall_enter"
and "kvm_hv:kvm_hcall_exit". It uses the pSeries hypervisor codes
exported through uapi to classify the hcalls into their respective reasons.

# pgrep qemu
A sample output :
19378
60515

2 VMs running.

# perf kvm stat record -a
^C[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 4.153 MB perf.data.guest (39624 samples) ]

# perf kvm stat report -p 60515 --event=hcall
Analyze events for pid(s) 60515, all VCPUs:

HCALL-EVENT Samples Samples% Time% Min Time Max Time Avg time

H_VIO_SIGNAL 1034 38.44% 15.77% 0.36us 1.59us 0.44us ( +- 0.66% )
H_SEND_CRQ 652 24.24% 10.97% 0.39us 1.84us 0.49us ( +- 1.20% )
H_IPI 523 19.44% 62.05% 1.35us 19.70us 3.44us ( +- 2.88% )
H_PUT_TERM_CHAR 411 15.28% 8.03% 0.38us 3.77us 0.57us ( +- 1.61% )
H_GET_TERM_CHAR 50 1.86% 0.99% 0.40us 0.98us 0.57us ( +- 3.37% )
H_EOI 20 0.74% 2.19% 2.22us 4.72us 3.17us ( +- 5.96% )

Total Samples:2690, Total events handled time:2896.94us.

Signed-off-by: Hemant Kumar <hemant@linux.vnet.ibm.com>
---
arch/powerpc/include/uapi/asm/kvm_perf.h | 4 +++
tools/perf/arch/powerpc/util/kvm-stat.c | 61 ++++++++++++++++++++++++++++++++
2 files changed, 65 insertions(+)

diff --git a/arch/powerpc/include/uapi/asm/kvm_perf.h b/arch/powerpc/include/uapi/asm/kvm_perf.h
index 30fa670..440902e 100644
--- a/arch/powerpc/include/uapi/asm/kvm_perf.h
+++ b/arch/powerpc/include/uapi/asm/kvm_perf.h
@@ -3,6 +3,7 @@

#include <asm/trace_book3s.h>
#include <asm/kvm.h>
+#include <asm/trace_hcall.h>

#define DECODE_STR_LEN 20

@@ -11,5 +12,8 @@
#define KVM_ENTRY_TRACE "kvm_hv:kvm_guest_enter"
#define KVM_EXIT_TRACE "kvm_hv:kvm_guest_exit"
#define KVM_EXIT_REASON "trap"
+#define KVM_HCALL_ENTRY_TRACE "kvm_hv:kvm_hcall_enter"
+#define KVM_HCALL_EXIT_TRACE "kvm_hv:kvm_hcall_exit"
+#define KVM_HCALL_REASON "req"

#endif /* _ASM_POWERPC_KVM_PERF_H */
diff --git a/tools/perf/arch/powerpc/util/kvm-stat.c b/tools/perf/arch/powerpc/util/kvm-stat.c
index 62cdcc1..685201c 100644
--- a/tools/perf/arch/powerpc/util/kvm-stat.c
+++ b/tools/perf/arch/powerpc/util/kvm-stat.c
@@ -1,7 +1,9 @@
#include "../../util/kvm-stat.h"
#include <asm/kvm_perf.h>
+#include "../../util/debug.h"

define_exit_reasons_table(hv_exit_reasons, kvm_trace_symbol_exit);
+define_exit_reasons_table(hcall_reasons, kvm_trace_symbol_hcall);

static struct kvm_events_ops exit_events = {
.is_begin_event = exit_event_begin,
@@ -10,14 +12,73 @@ static struct kvm_events_ops exit_events = {
.name = "VM-EXIT"
};

+static void hcall_event_get_key(struct perf_evsel *evsel,
+ struct perf_sample *sample,
+ struct event_key *key)
+{
+ key->info = 0;
+ key->key = perf_evsel__intval(evsel, sample, KVM_HCALL_REASON);
+}
+
+static const char *get_exit_reason(u64 exit_code)
+{
+ struct exit_reasons_table *tbl = hcall_reasons;
+
+ while (tbl->reason != NULL) {
+ if (tbl->exit_code == exit_code)
+ return tbl->reason;
+ tbl++;
+ }
+
+ pr_err("Unknown kvm hcall exit code: %lld\n",
+ (unsigned long long)exit_code);
+ return "UNKNOWN";
+}
+
+static bool hcall_event_end(struct perf_evsel *evsel,
+ struct perf_sample *sample __maybe_unused,
+ struct event_key *key __maybe_unused)
+{
+ return (!strcmp(evsel->name, KVM_HCALL_EXIT_TRACE));
+}
+
+static bool hcall_event_begin(struct perf_evsel *evsel,
+ struct perf_sample *sample, struct event_key *key)
+{
+ if (!strcmp(evsel->name, KVM_HCALL_ENTRY_TRACE)) {
+ hcall_event_get_key(evsel, sample, key);
+ return true;
+ }
+
+ return false;
+}
+static void hcall_event_decode_key(struct perf_kvm_stat *kvm __maybe_unused,
+ struct event_key *key,
+ char *decode)
+{
+ const char *hcall_reason = get_exit_reason(key->key);
+
+ scnprintf(decode, DECODE_STR_LEN, "%s", hcall_reason);
+}
+
+static struct kvm_events_ops hcall_events = {
+ .is_begin_event = hcall_event_begin,
+ .is_end_event = hcall_event_end,
+ .decode_key = hcall_event_decode_key,
+ .name = "HCALL-EVENT",
+};
+
const char *const kvm_events_tp[] = {
"kvm_hv:kvm_guest_exit",
"kvm_hv:kvm_guest_enter",
+ "kvm_hv:kvm_hcall_enter",
+ "kvm_hv:kvm_hcall_exit",
NULL,
};

struct kvm_reg_events_ops kvm_reg_events_ops[] = {
{ .name = "vmexit", .ops = &exit_events },
+ { .name = "hcall", .ops = &hcall_events },
{ NULL, NULL },
};

--
1.9.3


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