Re: [libvirt] [PATCH v2 3/8] perf: implement a set of util functions for perf event

8 Dec 2015


      On Mon, Dec 07, 2015 at 03:53:54PM +0800, Qiaowei Ren wrote:
...
This patch implement a set of interfaces for perf event. Based on
these interfaces, we can implement internal driver API for perf,
and get the results of perf conuter you care about.
Signed-off-by: Qiaowei Ren <qiaowei.ren@intel.com>
---
 include/libvirt/virterror.h |   1 +
 src/Makefile.am             |   1 +
 src/libvirt_private.syms    |  12 ++
 src/util/virerror.c         |   1 +
 src/util/virperf.c          | 298 ++++++++++++++++++++++++++++++++++++++++++++
 src/util/virperf.h          |  61 +++++++++
 6 files changed, 374 insertions(+)
 create mode 100644 src/util/virperf.c
 create mode 100644 src/util/virperf.h

...
+VIR_ENUM_IMPL(virPerfEvent, VIR_PERF_EVENT_LAST,
+              "cmt");
+
+struct virPerfEvent {
+    int type;
+    int fd;
+    bool enabled;
+    union {
+        /* cmt */
+        struct {
+            int scale;
+        } cmt;
+    } efields;
+};
+typedef struct virPerfEvent *virPerfEventPtr;
+
+struct virPerf {
+    struct virPerfEvent events[VIR_PERF_EVENT_LAST];
+};
+
+virPerfPtr
+virPerfNew(void)
+{
+    size_t i;
+    virPerfPtr perf;
+
+    if (VIR_ALLOC(perf) < 0)
+        return NULL;
+
+    for (i = 0; i < VIR_PERF_EVENT_LAST; i++) {
+        perf->events[i].type = i;
+        perf->events[i].fd = -1;
+        perf->events[i].enabled = false;
+    }
+
+    return perf;
+}
+
+void
+virPerfFree(virPerfPtr perf)
+{
+    size_t i;
+
+    if (perf == NULL)
+        return;
+
+    for (i = 0; i < VIR_PERF_EVENT_LAST; i++) {
+        if (perf->events[i].enabled)
+            virPerfEventDisable(perf, i);
+    }
+
+    VIR_FREE(perf);
+}
+
+#if defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)
+
+# include <linux/perf_event.h>
+
+static virPerfEventPtr
+virPerfGetEvent(virPerfPtr perf,
+                virPerfEventType type)
+{
+    if (type >= VIR_PERF_EVENT_LAST) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Event '%d' is not supported"),
+                       type);
+        return NULL;
+    }
+
+    return perf->events + type;
+}
+
+static int
+virPerfCmtEnable(virPerfEventPtr event,
+                 pid_t pid)
+{
+    struct perf_event_attr cmt_attr;
+    int event_type;
+    FILE *fp = NULL;
+    FILE *fp_scale = NULL;
+    int scale = 0;
+
+    fp = fopen("/sys/devices/intel_cqm/type", "r");
+    if (!fp) {
+        virReportSystemError(errno, "%s",
+                             _("CMT is not available on this host"));
+        return -1;
+    }
+    if (fscanf(fp, "%d", &event_type) != 1) {
+        virReportSystemError(errno, "%s",
+                             _("Unable to read event type file."));
+        goto cleanup;
+    }
Scanf has pretty poor error reporting, so we'd usually do

   char *buf;
   if (virFileReadAll("/path", 100, &buf) < 0)
        return -1;

   if (virStrToLong_ui(buf, NULL, 10, &scale) < 0) {
       VIR_FREE(buf);
        ....report error...
	return -1;
   }

   VIR_FREE(buf);
...
+
+    fp_scale = fopen("/sys/devices/intel_cqm/events/llc_occupancy.scale", "r");
+    if (!fp_scale) {
+        virReportSystemError(errno, "%s",
+                             _("Unable to open CMT scale file"));
+        goto cleanup;
+    }
+    if (fscanf(fp_scale, "%d", &scale) != 1) {
+        virReportSystemError(errno, "%s",
+                             _("Unable to read CMT scale file"));
+        goto cleanup;
+    }
Same comment here.
...
+    event->efields.cmt.scale = scale;
+
+    memset(&cmt_attr, 0, sizeof(cmt_attr));
+    cmt_attr.size = sizeof(cmt_attr);
+    cmt_attr.type = event_type;
+    cmt_attr.config = 1;
+    cmt_attr.inherit = 1;
+    cmt_attr.disabled = 1;
+    cmt_attr.enable_on_exec = 0;
+
+    event->fd = syscall(__NR_perf_event_open, &cmt_attr, pid, -1, -1, 0);
+    if (event->fd < 0) {
+        virReportSystemError(errno,
+                             _("Unable to open perf type=%d for pid=%d"),
+                             event_type, pid);
+        goto cleanup;
+    }
+
+    if (ioctl(event->fd, PERF_EVENT_IOC_ENABLE) < 0) {
+        virReportSystemError(errno, "%s",
+                             _("Unable to enable perf event for CMT"));
+        goto cleanup;
+    }
+
+    event->enabled = true;
+    return 0;
+
+ cleanup:
+    if (fp)
+        VIR_FORCE_FCLOSE(fp);
+    if (fp_scale)
+        VIR_FORCE_FCLOSE(fp_scale);
+    if (event->fd >= 0)
+        VIR_FORCE_CLOSE(event->fd);
+    return -1;
...
+int
+virPerfEventDisable(virPerfPtr perf,
+                    virPerfEventType type)
+{
+    virPerfEventPtr event = virPerfGetEvent(perf, type);
+    if (event == NULL)
+        return -1;
+
+    if (ioctl(event->fd, PERF_EVENT_IOC_DISABLE) < 0) {
+        virReportSystemError(errno,
+                             _("Unable to disable perf event type=%d"),
+                             event->type);
+        return -1;
+    }
Since we're closing the file handle next, is there any benefit
in doing this ioctl() ?
...
+
+    event->enabled = false;
+    VIR_FORCE_CLOSE(event->fd);
+    return 0;
+}
Regards,
Daniel
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Re: [libvirt] [PATCH v2 3/8] perf: implement a set of util functions for perf event

Daniel P. Berrange