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Date: Thu, 30 Aug 2012 12:29:25 -0600
From: David Ahern <dsahern@...il.com>
To: Dong Hao <haodong@...ux.vnet.ibm.com>
CC: avi@...hat.com, acme@...radead.org, mtosatti@...hat.com,
mingo@...e.hu, xiaoguangrong@...ux.vnet.ibm.com,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v7 3/3] KVM: perf: kvm events analysis tool
In addition to Andrew's comment about making the stats struct and
functions generic...
On 8/27/12 3:51 AM, Dong Hao wrote:
---8<---
> +static void exit_event_decode_key(struct event_key *key, char decode[20])
> +{
> + const char *exit_reason = get_exit_reason(key->key);
> +
> + snprintf(decode, 20, "%s", exit_reason);
> +}
Use scnprintf rather than snprintf.
---8<---
> +static bool kvm_event_expand(struct kvm_event *event, int vcpu_id)
> +{
> + int old_max_vcpu = event->max_vcpu;
> +
> + if (vcpu_id < event->max_vcpu)
> + return true;
> +
> + while (event->max_vcpu <= vcpu_id)
> + event->max_vcpu += DEFAULT_VCPU_NUM;
> +
> + event->vcpu = realloc(event->vcpu,
> + event->max_vcpu * sizeof(*event->vcpu));
> + if (!event->vcpu) {
If realloc fails you leak memory by overwriting the current pointer.
---8<---
> +static double event_stats_stddev(int vcpu_id, struct kvm_event *event)
> +{
> + struct event_stats *stats = &event->total;
> + double variance, variance_mean, stddev;
> +
> + if (vcpu_id != -1)
> + stats = &event->vcpu[vcpu_id];
> +
> + BUG_ON(!stats->count);
> +
> + variance = stats->M2 / (stats->count - 1);
> + variance_mean = variance / stats->count;
> + stddev = sqrt(variance_mean);
> +
> + return stddev * 100 / stats->mean;
> +}
perf should be consistent in the stddev it shows the user. Any reason to
dump relative stddev versus stddev used by perf-stat?
---8<---
> +/* returns left most element of result, and erase it */
> +static struct kvm_event *pop_from_result(void)
> +{
> + struct rb_node *node = result.rb_node;
> +
> + if (!node)
> + return NULL;
> +
> + while (node->rb_left)
> + node = node->rb_left;
Use rb_first().
---8<---
> + /*
> + * Append "-a" only if "-p"/"--pid" is not specified since they
> + * are mutually exclusive.
> + */
> + if (!kvm_record_specified_guest(argc, argv))
> + rec_argv[i++] = STRDUP_FAIL_EXIT("-a");
Other perf-kvm commands rely on perf-record semantics -- i.e., for user
to add the -a or -p option.
---8<---
> +static const char * const kvm_events_report_usage[] = {
> + "perf kvm stat report [<options>]",
> + NULL
> +};
> +
> +static const struct option kvm_events_report_options[] = {
> + OPT_STRING(0, "event", &report_event, "report event",
> + "event for reporting: vmexit, mmio, ioport"),
> + OPT_INTEGER(0, "vcpu", &trace_vcpu,
> + "vcpu id to report"),
> + OPT_STRING('k', "key", &sort_key, "sort-key",
> + "key for sorting: sample(sort by samples number)"
> + " time (sort by avg time)"),
> + OPT_END()
> +};
> +
> +static int kvm_events_report(int argc, const char **argv)
> +{
> + symbol__init();
> +
> + if (argc) {
> + argc = parse_options(argc, argv,
> + kvm_events_report_options,
> + kvm_events_report_usage, 0);
> + if (argc)
> + usage_with_options(kvm_events_report_usage,
> + kvm_events_report_options);
> + }
> +
> + return kvm_events_report_vcpu(trace_vcpu);
> +}
> +
> +static int kvm_cmd_stat(int argc, const char **argv)
> +{
> + if (argc > 1) {
> + if (!strncmp(argv[1], "rec", 3))
> + return kvm_events_record(argc - 1, argv + 1);
> +
> + if (!strncmp(argv[1], "rep", 3))
> + return kvm_events_report(argc - 1 , argv + 1);
> + }
> +
> + return cmd_stat(argc, argv, NULL);
> +}
> +
> static char name_buffer[256];
>
> static const char * const kvm_usage[] = {
> - "perf kvm [<options>] {top|record|report|diff|buildid-list}",
> + "perf kvm [<options>] {top|record|report|diff|buildid-list|stat}",
> NULL
> };
>
The usage for the report/record sub commands of stat is never shown. e.g.,
$ perf kvm stat
--> shows help for perf-stat
$ perf kvm
--> shows the above and perf-kvm's usage
To get help for the record/report subcommands you have to know that
record and report are subcommands.
---8<---
> +static int perf_file_section__read_feature(struct perf_file_section *section,
> + struct perf_header *ph,
> + int feat, int fd, void *data)
> +{
> + struct header_read_data *hd = data;
> +
> + if (feat != hd->feat)
> + return 0;
> +
> + if (lseek(fd, section->offset, SEEK_SET) == (off_t)-1) {
> + pr_debug("Failed to lseek to %" PRIu64 " offset for feature "
> + "%d, continuing...\n", section->offset, feat);
> + return 0;
> + }
> +
> + if (feat >= HEADER_LAST_FEATURE) {
> + pr_warning("unknown feature %d\n", feat);
> + return 0;
> + }
> +
> + hd->result = feat_ops[feat].read(ph, fd);
you should verify the read() function is implemented for the requested
feature.
David
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