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Re: [PATCH v2] plugins/syscall: Added a table-like summary output
From: |
Alex Bennée |
Subject: |
Re: [PATCH v2] plugins/syscall: Added a table-like summary output |
Date: |
Mon, 19 Apr 2021 11:23:30 +0100 |
User-agent: |
mu4e 1.5.11; emacs 28.0.50 |
Mahmoud Mandour <ma.mandourr@gmail.com> writes:
> Added a table-like output which contains the total number of calls
> for each used syscall along with the number of errors that occurred.
>
> Per-call tracing is still available through supplying the argument
> ``print`` to the plugin.
>
> Signed-off-by: Mahmoud Mandour <ma.mandourr@gmail.com>
> ---
> v1: https://lists.gnu.org/archive/html/qemu-devel/2021-04/msg02623.html
> v1 -> v2: Removed debugging code in the on-return from syscall callback
> that was silently existent.
>
> tests/plugin/syscall.c | 91 +++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 85 insertions(+), 6 deletions(-)
>
> diff --git a/tests/plugin/syscall.c b/tests/plugin/syscall.c
> index 53ee2ab6c4..b66a930635 100644
> --- a/tests/plugin/syscall.c
> +++ b/tests/plugin/syscall.c
> @@ -16,32 +16,111 @@
>
> QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
>
> +typedef struct {
> + int64_t calls;
> + int64_t errors;
> +} SyscallStats;
> +
> +static GHashTable *syscalls_statistics;
> +
> +static bool percall_print;
> +
> static void vcpu_syscall(qemu_plugin_id_t id, unsigned int vcpu_index,
> int64_t num, uint64_t a1, uint64_t a2,
> uint64_t a3, uint64_t a4, uint64_t a5,
> uint64_t a6, uint64_t a7, uint64_t a8)
> {
> - g_autofree gchar *out = g_strdup_printf("syscall #%" PRIi64 "\n", num);
> - qemu_plugin_outs(out);
> + if (!percall_print) {
I think you could eliminate the percall_print global and just invert the
test and have if (syscall_statisitics)
> + SyscallStats *syscall_entry;
> +
> + syscall_entry =
> + (SyscallStats *) g_hash_table_lookup(syscalls_statistics,
> + GINT_TO_POINTER(num));
> +
> + if (!syscall_entry) {
> + syscall_entry = g_new(SyscallStats, 1);
> + syscall_entry->calls = 1;
> + syscall_entry->errors = 0;
> +
> + g_hash_table_insert(syscalls_statistics, GINT_TO_POINTER(num),
> + (gpointer) syscall_entry);
You you wrap up the entry creation into a helper it would make the code
less cluttered here, e.g.:
syscall_entry = get_or_create_entry();
syscall_entry->calls++;
> + } else {
> + syscall_entry->calls++;
> + }
> + } else {
> + g_autofree gchar *out = g_strdup_printf("syscall #%" PRIi64 "\n",
> num);
> + qemu_plugin_outs(out);
> + }
> }
>
> static void vcpu_syscall_ret(qemu_plugin_id_t id, unsigned int vcpu_idx,
> int64_t num, int64_t ret)
> +{
> + if (!percall_print) {
> + SyscallStats *syscall_entry;
> +
> + syscall_entry =
> + (SyscallStats *) g_hash_table_lookup(syscalls_statistics,
> + GINT_TO_POINTER(num));
> + if (ret < 0) {
> + syscall_entry->errors++;
> + }
> + } else {
> + g_autofree gchar *out;
> + out = g_strdup_printf("syscall #%" PRIi64 " returned -> %" PRIi64
> "\n",
> + num, ret);
> + qemu_plugin_outs(out);
> + }
ditto.
> +}
> +
> +/* *************************************************************************
> */
> +
> +void print_entry(gpointer key, gpointer val, gpointer user_data)
> {
> g_autofree gchar *out;
> - out = g_strdup_printf("syscall #%" PRIi64 " returned -> %" PRIi64 "\n",
> - num, ret);
> + int64_t syscall_num = (int64_t) key;
> + SyscallStats *syscall_entry = (SyscallStats *) val;
> + out = g_strdup_printf(
> + "%-13" PRIi64 "%-6" PRIi64 " %" PRIi64 "\n",
> + syscall_num, syscall_entry->calls, syscall_entry->errors);
> qemu_plugin_outs(out);
> }
>
> -/* *************************************************************************
> */
> +static void plugin_exit(qemu_plugin_id_t id, void *p)
> +{
> + if (!percall_print) {
> + qemu_plugin_outs("syscall no. calls errors\n");
> + g_hash_table_foreach(syscalls_statistics, &print_entry,
> NULL);
Sorting the hash list by calls would be a nice improvement - see howvec
for an example of how to use g_hash_table_get_values/g_list_sort.
For cleanliness you should also clean-up the syscall_statisitics hash
table and deallocation although in practice it doesn't really matter as
use space is about to exit anyway.
> + }
> +}
>
> -static void plugin_exit(qemu_plugin_id_t id, void *p) {}
> +void free_entry(gpointer entry)
> +{
> + g_free(entry);
> +}
>
> QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
> const qemu_info_t *info,
> int argc, char **argv)
> {
> + int i;
> +
> + for (i = 0; i < argc; i++) {
> + char *opt = argv[i];
> + if (g_strcmp0(opt, "print") == 0) {
> + percall_print = true;
So this would be a local now and or even:
if (argc == 0) {
syscalls_statistics = g_hash_table_new_full(g_direct_hash,
g_direct_equal, NULL, &free_entry);
} else {
for (i = 0; i < argc; i++) {
...
> + } else {
> + fprintf(stderr, "unsupported argument: %s\n", opt);
> + return -1;
> + }
> + }
> +
> + if (!percall_print) {
> + syscalls_statistics =
> + g_hash_table_new_full(g_direct_hash, g_direct_equal,
> + NULL, &free_entry);
For a simple non-nested structure you might even get away with a plain
g_hash_table_new()
> + }
> +
> qemu_plugin_register_vcpu_syscall_cb(id, vcpu_syscall);
> qemu_plugin_register_vcpu_syscall_ret_cb(id, vcpu_syscall_ret);
> qemu_plugin_register_atexit_cb(id, plugin_exit, NULL);
--
Alex Bennée