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Date: Tue, 10 Aug 2021 09:33:50 +0900
From: Masami Hiramatsu <mhiramat@...nel.org>
To: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
Tom Zanussi <zanussi@...nel.org>
Subject: Re: [PATCH v2 02/10] tracing/boot: Add per-event histogram action
options
On Tue, 10 Aug 2021 00:48:04 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:
> Add a hist-trigger action syntax support to boot-time tracing.
> Currently, boot-time tracing supports per-event actions as option
> strings. However, for the histogram action, it has a special syntax
> and usually needs a long action definition.
> To make it readable and fit to the bootconfig syntax, this introduces
> a new options for histogram.
>
> Here are the histogram action options for boot-time tracing.
>
> ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist {
> keys = <KEY>[,...]
> values = <VAL>[,...]
> sort = <SORT-KEY>[,...]
> size = <ENTRIES>
> name = <HISTNAME>
> var { <VAR> = <EXPR> ... }
> pause|continue|clear
> onmax|onchange { var = <VAR>; <ACTION> [= <PARAM>] }
> onmatch { event = <EVENT>; <ACTION> [= <PARAM>] }
> filter = <FILTER>
> }
>
> Where <ACTION> is one of below;
>
> trace = <EVENT>, <ARG1>[, ...]
> save = <ARG1>[, ...]
> snapshot
>
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
> Changes in v3:
> - Allow var expression includes spaces, since it is natural that
> user write an expression with space in bootconfig.
> (e.g. "var.lat = common_timestamp.usecs - $ts0")
> Changes in v2:
> - Cleanup code to add ':' as a prefix for each element
> instead of fixup the last ':'.
> - Fix syntax typo for handler actions.
> - Make pause|continue|clear mutual exclusive.
> - Add __printf() attribute to the append_printf().
> ---
> kernel/trace/trace_boot.c | 231 +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 231 insertions(+)
>
> diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
> index d713714cba67..763f8a7b7e1b 100644
> --- a/kernel/trace/trace_boot.c
> +++ b/kernel/trace/trace_boot.c
> @@ -171,6 +171,231 @@ trace_boot_add_synth_event(struct xbc_node *node, const char *event)
> }
> #endif
>
> +#ifdef CONFIG_HIST_TRIGGERS
> +static int __init __printf(3, 4)
> +append_printf(char **bufp, char *end, const char *fmt, ...)
> +{
> + va_list args;
> + int ret;
> +
> + if (*bufp == end)
> + return -ENOSPC;
> +
> + va_start(args, fmt);
> + ret = vsnprintf(*bufp, end - *bufp, fmt, args);
> + if (ret < end - *bufp) {
> + *bufp += ret;
> + } else {
> + *bufp = end;
> + ret = -ERANGE;
> + }
> + va_end(args);
> +
> + return ret;
> +}
> +
> +static int __init
> +append_str_nospace(char **bufp, char *end, char *str)
Kbuild bot reported that I missed 'const' for the @str. Indeed, it's correct.
Let me update the series.
Thank you,
> +{
> + char *p = *bufp;
> + int len;
> +
> + while (p < end - 1 && *str != '\0') {
> + if (!isspace(*str))
> + *(p++) = *str;
> + str++;
> + }
> + *p = '\0';
> + if (p == end - 1) {
> + *bufp = end;
> + return -ENOSPC;
> + }
> + len = p - *bufp;
> + *bufp = p;
> + return (int)len;
> +}
> +
> +static int __init
> +trace_boot_hist_add_array(struct xbc_node *hnode, char **bufp,
> + char *end, const char *key)
> +{
> + struct xbc_node *knode, *anode;
> + const char *p;
> + char sep;
> +
> + knode = xbc_node_find_child(hnode, key);
> + if (knode) {
> + anode = xbc_node_get_child(knode);
> + if (!anode) {
> + pr_err("hist.%s requires value(s).\n", key);
> + return -EINVAL;
> + }
> +
> + append_printf(bufp, end, ":%s", key);
> + sep = '=';
> + xbc_array_for_each_value(anode, p) {
> + append_printf(bufp, end, "%c%s", sep, p);
> + if (sep == '=')
> + sep = ',';
> + }
> + } else
> + return -ENOENT;
> +
> + return 0;
> +}
> +
> +static int __init
> +trace_boot_hist_add_handler(struct xbc_node *hnode, char **bufp,
> + char *end, const char *param)
> +{
> + struct xbc_node *knode, *anode;
> + const char *p;
> + char sep;
> +
> + /* Compose 'handler' parameter */
> + p = xbc_node_find_value(hnode, param, NULL);
> + if (!p) {
> + pr_err("hist.%s requires '%s' option.\n",
> + xbc_node_get_data(hnode), param);
> + return -EINVAL;
> + }
> + append_printf(bufp, end, ":%s(%s)", xbc_node_get_data(hnode), p);
> +
> + /* Compose 'action' parameter */
> + knode = xbc_node_find_child(hnode, "trace");
> + if (!knode)
> + knode = xbc_node_find_child(hnode, "save");
> +
> + if (knode) {
> + anode = xbc_node_get_child(knode);
> + if (!anode || !xbc_node_is_value(anode)) {
> + pr_err("hist.%s.%s requires value(s).\n",
> + xbc_node_get_data(hnode),
> + xbc_node_get_data(knode));
> + return -EINVAL;
> + }
> +
> + append_printf(bufp, end, ".%s", xbc_node_get_data(knode));
> + sep = '(';
> + xbc_array_for_each_value(anode, p) {
> + append_printf(bufp, end, "%c%s", sep, p);
> + if (sep == '(')
> + sep = ',';
> + }
> + append_printf(bufp, end, ")");
> + } else if (xbc_node_find_child(hnode, "snapshot")) {
> + append_printf(bufp, end, ".snapshot()");
> + } else {
> + pr_err("hist.%s requires an action.\n",
> + xbc_node_get_data(hnode));
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +/*
> + * Histogram boottime tracing syntax.
> + *
> + * ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist {
> + * keys = <KEY>[,...]
> + * values = <VAL>[,...]
> + * sort = <SORT-KEY>[,...]
> + * size = <ENTRIES>
> + * name = <HISTNAME>
> + * var { <VAR> = <EXPR> ... }
> + * pause|continue|clear
> + * onmax|onchange { var = <VAR>; <ACTION> [= <PARAM>] }
> + * onmatch { event = <EVENT>; <ACTION> [= <PARAM>] }
> + * filter = <FILTER>
> + * }
> + *
> + * Where <ACTION> are;
> + *
> + * trace = <EVENT>, <ARG1>[, ...]
> + * save = <ARG1>[, ...]
> + * snapshot
> + */
> +static int __init
> +trace_boot_compose_hist_cmd(struct xbc_node *hnode, char *buf, size_t size)
> +{
> + struct xbc_node *node, *knode;
> + char *end = buf + size;
> + const char *p;
> + int ret = 0;
> +
> + append_printf(&buf, end, "hist");
> +
> + ret = trace_boot_hist_add_array(hnode, &buf, end, "keys");
> + if (ret < 0) {
> + if (ret == -ENOENT)
> + pr_err("hist requires keys.\n");
> + return -EINVAL;
> + }
> +
> + ret = trace_boot_hist_add_array(hnode, &buf, end, "values");
> + if (ret == -EINVAL)
> + return ret;
> + ret = trace_boot_hist_add_array(hnode, &buf, end, "sort");
> + if (ret == -EINVAL)
> + return ret;
> +
> + p = xbc_node_find_value(hnode, "size", NULL);
> + if (p)
> + append_printf(&buf, end, ":size=%s", p);
> +
> + p = xbc_node_find_value(hnode, "name", NULL);
> + if (p)
> + append_printf(&buf, end, ":name=%s", p);
> +
> + node = xbc_node_find_child(hnode, "var");
> + if (node) {
> + xbc_node_for_each_key_value(node, knode, p) {
> + /* Expression must not include spaces. */
> + append_printf(&buf, end, ":%s=",
> + xbc_node_get_data(knode));
> + append_str_nospace(&buf, end, p);
> + }
> + }
> +
> + /* Histogram control attributes (mutual exclusive) */
> + if (xbc_node_find_child(hnode, "pause"))
> + append_printf(&buf, end, ":pause");
> + else if (xbc_node_find_child(hnode, "continue"))
> + append_printf(&buf, end, ":continue");
> + else if (xbc_node_find_child(hnode, "clear"))
> + append_printf(&buf, end, ":clear");
> +
> + /* Histogram handler and actions */
> + node = xbc_node_find_child(hnode, "onmax");
> + if (node && trace_boot_hist_add_handler(node, &buf, end, "var") < 0)
> + return -EINVAL;
> + node = xbc_node_find_child(hnode, "onchange");
> + if (node && trace_boot_hist_add_handler(node, &buf, end, "var") < 0)
> + return -EINVAL;
> + node = xbc_node_find_child(hnode, "onmatch");
> + if (node && trace_boot_hist_add_handler(node, &buf, end, "event") < 0)
> + return -EINVAL;
> +
> + p = xbc_node_find_value(hnode, "filter", NULL);
> + if (p)
> + append_printf(&buf, end, " if %s", p);
> +
> + if (buf == end) {
> + pr_err("hist exceeds the max command length.\n");
> + return -E2BIG;
> + }
> +
> + return 0;
> +}
> +#else
> +static int __init
> +trace_boot_compose_hist_cmd(struct xbc_node *hnode, char *buf, size_t size)
> +{
> + return -EOPNOTSUPP;
> +}
> +#endif
> +
> static void __init
> trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
> struct xbc_node *enode)
> @@ -212,6 +437,12 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
> else if (trigger_process_regex(file, buf) < 0)
> pr_err("Failed to apply an action: %s\n", buf);
> }
> + anode = xbc_node_find_child(enode, "hist");
> + if (anode &&
> + trace_boot_compose_hist_cmd(anode, buf, ARRAY_SIZE(buf)) == 0) {
> + if (trigger_process_regex(file, buf) < 0)
> + pr_err("Failed to apply hist trigger: %s\n", buf);
> + }
> } else if (xbc_node_find_value(enode, "actions", NULL))
> pr_err("Failed to apply event actions because CONFIG_HIST_TRIGGERS is not set.\n");
>
>
--
Masami Hiramatsu <mhiramat@...nel.org>
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