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Message-Id: <20211025200852.3002369-6-kaleshsingh@google.com>
Date: Mon, 25 Oct 2021 13:08:37 -0700
From: Kalesh Singh <kaleshsingh@...gle.com>
To: unlisted-recipients:; (no To-header on input)
Cc: surenb@...gle.com, hridya@...gle.com, namhyung@...nel.org,
kernel-team@...roid.com, Kalesh Singh <kaleshsingh@...gle.com>,
Steven Rostedt <rostedt@...dmis.org>,
Jonathan Corbet <corbet@....net>,
Ingo Molnar <mingo@...hat.com>, Shuah Khan <shuah@...nel.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Tom Zanussi <zanussi@...nel.org>, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: [PATCH v4 5/8] tracing/histogram: Covert expr to const if both
operands are constants
If both operands of a hist trigger expression are constants, convert the
expression to a constant. This optimization avoids having to perform the
same calculation multiple times and also saves on memory since the
merged constants are represented by a single struct hist_field instead
or multiple.
Signed-off-by: Kalesh Singh <kaleshsingh@...gle.com>
Suggested-by: Steven Rostedt <rostedt@...dmis.org>
---
kernel/trace/trace_events_hist.c | 104 ++++++++++++++++++++++---------
1 file changed, 74 insertions(+), 30 deletions(-)
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 34aba07d23f8..db28bcf976f4 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -2411,9 +2411,15 @@ static struct hist_field *parse_unary(struct hist_trigger_data *hist_data,
return ERR_PTR(ret);
}
+/*
+ * If the operands are var refs, return pointers the
+ * variable(s) referenced in var1 and var2, else NULL.
+ */
static int check_expr_operands(struct trace_array *tr,
struct hist_field *operand1,
- struct hist_field *operand2)
+ struct hist_field *operand2,
+ struct hist_field **var1,
+ struct hist_field **var2)
{
unsigned long operand1_flags = operand1->flags;
unsigned long operand2_flags = operand2->flags;
@@ -2426,6 +2432,7 @@ static int check_expr_operands(struct trace_array *tr,
if (!var)
return -EINVAL;
operand1_flags = var->flags;
+ *var1 = var;
}
if ((operand2_flags & HIST_FIELD_FL_VAR_REF) ||
@@ -2436,6 +2443,7 @@ static int check_expr_operands(struct trace_array *tr,
if (!var)
return -EINVAL;
operand2_flags = var->flags;
+ *var2 = var;
}
if ((operand1_flags & HIST_FIELD_FL_TIMESTAMP_USECS) !=
@@ -2453,9 +2461,12 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
char *var_name, unsigned int *n_subexprs)
{
struct hist_field *operand1 = NULL, *operand2 = NULL, *expr = NULL;
- unsigned long operand_flags;
+ struct hist_field *var1 = NULL, *var2 = NULL;
+ unsigned long operand_flags, operand2_flags;
int field_op, ret = -EINVAL;
char *sep, *operand1_str;
+ hist_field_fn_t op_fn;
+ bool combine_consts;
if (*n_subexprs > 3) {
hist_err(file->tr, HIST_ERR_TOO_MANY_SUBEXPR, errpos(str));
@@ -2512,11 +2523,38 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
goto free;
}
- ret = check_expr_operands(file->tr, operand1, operand2);
+ switch (field_op) {
+ case FIELD_OP_MINUS:
+ op_fn = hist_field_minus;
+ break;
+ case FIELD_OP_PLUS:
+ op_fn = hist_field_plus;
+ break;
+ case FIELD_OP_DIV:
+ op_fn = hist_field_div;
+ break;
+ case FIELD_OP_MULT:
+ op_fn = hist_field_mult;
+ break;
+ default:
+ ret = -EINVAL;
+ goto free;
+ }
+
+ ret = check_expr_operands(file->tr, operand1, operand2, &var1, &var2);
if (ret)
goto free;
- flags |= HIST_FIELD_FL_EXPR;
+ operand_flags = var1 ? var1->flags : operand1->flags;
+ operand2_flags = var2 ? var2->flags : operand2->flags;
+
+ /*
+ * If both operands are constant, the expression can be
+ * collapsed to a single constant.
+ */
+ combine_consts = operand_flags & operand2_flags & HIST_FIELD_FL_CONST;
+
+ flags |= combine_consts ? HIST_FIELD_FL_CONST : HIST_FIELD_FL_EXPR;
flags |= operand1->flags &
(HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS);
@@ -2533,37 +2571,43 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
expr->operands[0] = operand1;
expr->operands[1] = operand2;
- /* The operand sizes should be the same, so just pick one */
- expr->size = operand1->size;
+ if (combine_consts) {
+ if (var1)
+ expr->operands[0] = var1;
+ if (var2)
+ expr->operands[1] = var2;
- expr->operator = field_op;
- expr->name = expr_str(expr, 0);
- expr->type = kstrdup_const(operand1->type, GFP_KERNEL);
- if (!expr->type) {
- ret = -ENOMEM;
- goto free;
- }
+ expr->constant = op_fn(expr, NULL, NULL, NULL, NULL);
- switch (field_op) {
- case FIELD_OP_MINUS:
- expr->fn = hist_field_minus;
- break;
- case FIELD_OP_PLUS:
- expr->fn = hist_field_plus;
- break;
- case FIELD_OP_DIV:
- expr->fn = hist_field_div;
- break;
- case FIELD_OP_MULT:
- expr->fn = hist_field_mult;
- break;
- default:
- ret = -EINVAL;
- goto free;
+ expr->operands[0] = NULL;
+ expr->operands[1] = NULL;
+
+ /*
+ * var refs won't be destroyed immediately
+ * See: destroy_hist_field()
+ */
+ destroy_hist_field(operand2, 0);
+ destroy_hist_field(operand1, 0);
+
+ expr->name = expr_str(expr, 0);
+ } else {
+ expr->fn = op_fn;
+
+ /* The operand sizes should be the same, so just pick one */
+ expr->size = operand1->size;
+
+ expr->operator = field_op;
+ expr->type = kstrdup_const(operand1->type, GFP_KERNEL);
+ if (!expr->type) {
+ ret = -ENOMEM;
+ goto free;
+ }
+
+ expr->name = expr_str(expr, 0);
}
return expr;
- free:
+free:
destroy_hist_field(operand1, 0);
destroy_hist_field(operand2, 0);
destroy_hist_field(expr, 0);
--
2.33.0.1079.g6e70778dc9-goog
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