[DTrace-devel] [PATCH v2 6/8] fbt: performance improvements

[Eugene Loh]

Reviewed-by: Eugene Loh <eugene.loh at oracle.com>
Also...

One patch or another needs to update the dt_module.[c|h] copyright years.

On 1/14/25 23:21, Kris Van Hees wrote:
> Up until now, FBT probes were registered for every symbol that was
> listed as traceable.  Most tracing session do not use most or even

s/session/sessions/

> any of these, and the process of registering them all was quite
> slow.
>
> diff --git a/libdtrace/dt_module.c b/libdtrace/dt_module.c
> @@ -1044,6 +1045,83 @@ dt_kern_module_find_ctf(dtrace_hdl_t *dtp, dt_module_t *dmp)
>   	}
>   }
>   
> +#define PROBE_LIST		TRACEFS "available_filter_functions"
> +
> +/*
> + * Determine which kernel functions are traceable and mark them.
> + */
> +void
> +dt_modsym_mark_traceable(dtrace_hdl_t *dtp)
> +{
> +	FILE			*f;
> +	char			*buf = NULL;
> +	size_t			len = 0;
> +
> +	if (dt_symtab_traceable(dtp->dt_exec->dm_kernsyms))
> +		return;
> +
> +	f = fopen(PROBE_LIST, "r");
> +	if (f == NULL)
> +		return;
> +
> +	while (getline(&buf, &len, f) >= 0) {
> +		char			*p;
> +		dt_symbol_t		*sym = NULL;
> +
> +		/*
> +		 * Here buf is either "funcname\n" or "funcname [modname]\n".
> +		 * The last line may not have a linefeed.
> +		 */
> +		p = strchr(buf, '\n');
> +		if (p) {
> +			*p = '\0';
> +			if (p > buf && *(--p) == ']')
> +				*p = '\0';
> +		}
> +
> +		/*
> +		 * Now buf is either "funcname" or "funcname [modname".  If
> +		 * there is no module name provided, we will use the default.
> +		 */

Maybe that second sentence is now orphaned?

> +		p = strchr(buf, ' ');
> +		if (p) {
> +			*p++ = '\0';
> +			if (*p == '[')
> +				p++;
> +		}
> +
> diff --git a/libdtrace/dt_prov_fbt.c b/libdtrace/dt_prov_fbt.c
> @@ -81,79 +71,166 @@ static int populate(dtrace_hdl_t *dtp)
>   	if (prv == NULL)
>   		return -1;			/* errno already set */
>   
> -	f = fopen(PROBE_LIST, "r");
> -	if (f == NULL)
> +	return 0;
> +}
> +
> +/* Create a probe (if it does not exist yet). */
> +static int provide_probe(dtrace_hdl_t *dtp, const dtrace_probedesc_t *pdp)
> +{
> +	dt_provider_t	*prv = dt_provider_lookup(dtp, pdp->prv);
> +
> +	if (prv == NULL)
> +		return 0;
> +	if (dt_probe_lookup(dtp, pdp) != NULL)
>   		return 0;
> +	if (dt_tp_probe_insert(dtp, prv, pdp->prv, pdp->mod, pdp->fun, pdp->prb))
> +		return 1;
>   
> -	while (getline(&buf, &n, f) >= 0) {
> -		/*
> -		 * Here buf is either "funcname\n" or "funcname [modname]\n".
> -		 * The last line may not have a linefeed.
> -		 */
> -		p = strchr(buf, '\n');
> -		if (p) {
> -			*p = '\0';
> -			if (p > buf && *(--p) == ']')
> -				*p = '\0';
> +	return 0;
> +}
> +
> +/*
> + * Try to provide probes for the given probe description.  The caller ensures
> + * that the provider name in probe desxcription (if any) is a match for this

desxcription
description

> + * provider.  When this is called, we already know that this provider matches
> + * the provider component of the probe specification.
> + */