Re: [PATCH v2 20/40] tracing: Add simple expression support to hist triggers

From: Steven Rostedt
Date: Thu Sep 07 2017 - 12:46:15 EST


On Tue, 5 Sep 2017 16:57:32 -0500
Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx> wrote:

> #define DEFINE_HIST_FIELD_FN(type) \
> static u64 hist_field_##type(struct hist_field *hist_field, \
> void *event, \
> @@ -148,6 +192,7 @@ enum hist_field_flags {
> HIST_FIELD_FL_TIMESTAMP_USECS = 2048,
> HIST_FIELD_FL_VAR = 4096,
> HIST_FIELD_FL_VAR_ONLY = 8192,
> + HIST_FIELD_FL_EXPR = 16384,

When numbers get this big, I'm a fan of:

HIST_FIELD_FL_TIMESTAMP_USECS = (1 << 11),
HIST_FIELD_FL_VAR = (1 << 12),
HIST_FIELD_FL_VAR_ONLY = (1 << 13),
HIST_FIELD_FL_EXPR = (1 << 14),

It makes it much easier to debug with printk()s and also know how many
bits you are actually using.

> };
>
> struct var_defs {
> @@ -218,6 +263,8 @@ static const char *hist_field_name(struct hist_field *field,
> field_name = hist_field_name(field->operands[0], ++level);
> else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
> field_name = "$common_timestamp";
> + else if (field->flags & HIST_FIELD_FL_EXPR)
> + field_name = field->name;
>
> if (field_name == NULL)
> field_name = "";
> @@ -441,6 +488,115 @@ static void hist_trigger_elt_comm_init(struct tracing_map_elt *elt)
> .elt_init = hist_trigger_elt_comm_init,
> };
>
> +static const char *get_hist_field_flags(struct hist_field *hist_field)
> +{
> + const char *flags_str = NULL;
> +
> + if (hist_field->flags & HIST_FIELD_FL_HEX)
> + flags_str = "hex";
> + else if (hist_field->flags & HIST_FIELD_FL_SYM)
> + flags_str = "sym";
> + else if (hist_field->flags & HIST_FIELD_FL_SYM_OFFSET)
> + flags_str = "sym-offset";
> + else if (hist_field->flags & HIST_FIELD_FL_EXECNAME)
> + flags_str = "execname";
> + else if (hist_field->flags & HIST_FIELD_FL_SYSCALL)
> + flags_str = "syscall";
> + else if (hist_field->flags & HIST_FIELD_FL_LOG2)
> + flags_str = "log2";
> + else if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP_USECS)
> + flags_str = "usecs";
> +
> + return flags_str;
> +}

Also, can you make the moving of the code a separate patch before this
patch. It makes git blame and such nicer.

-- Steve