[PATCH v2] tracing: uninline trace_trigger_soft_disabled() partly
From: Christophe Leroy
Date: Fri Feb 11 2022 - 02:10:44 EST
On a powerpc32 build with CONFIG_CC_OPTIMISE_FOR_SIZE, the inline
keyword is not honored and trace_trigger_soft_disabled() appears
approx 50 times in vmlinux.
Adding -Winline to the build, the following message appears:
./include/linux/trace_events.h:712:1: error: inlining failed in call to 'trace_trigger_soft_disabled': call is unlikely and code size would grow [-Werror=inline]
That function is rather big for an inlined function:
c003df60 <trace_trigger_soft_disabled>:
c003df60: 94 21 ff f0 stwu r1,-16(r1)
c003df64: 7c 08 02 a6 mflr r0
c003df68: 90 01 00 14 stw r0,20(r1)
c003df6c: bf c1 00 08 stmw r30,8(r1)
c003df70: 83 e3 00 24 lwz r31,36(r3)
c003df74: 73 e9 01 00 andi. r9,r31,256
c003df78: 41 82 00 10 beq c003df88 <trace_trigger_soft_disabled+0x28>
c003df7c: 38 60 00 00 li r3,0
c003df80: 39 61 00 10 addi r11,r1,16
c003df84: 4b fd 60 ac b c0014030 <_rest32gpr_30_x>
c003df88: 73 e9 00 80 andi. r9,r31,128
c003df8c: 7c 7e 1b 78 mr r30,r3
c003df90: 41 a2 00 14 beq c003dfa4 <trace_trigger_soft_disabled+0x44>
c003df94: 38 c0 00 00 li r6,0
c003df98: 38 a0 00 00 li r5,0
c003df9c: 38 80 00 00 li r4,0
c003dfa0: 48 05 c5 f1 bl c009a590 <event_triggers_call>
c003dfa4: 73 e9 00 40 andi. r9,r31,64
c003dfa8: 40 82 00 28 bne c003dfd0 <trace_trigger_soft_disabled+0x70>
c003dfac: 73 ff 02 00 andi. r31,r31,512
c003dfb0: 41 82 ff cc beq c003df7c <trace_trigger_soft_disabled+0x1c>
c003dfb4: 80 01 00 14 lwz r0,20(r1)
c003dfb8: 83 e1 00 0c lwz r31,12(r1)
c003dfbc: 7f c3 f3 78 mr r3,r30
c003dfc0: 83 c1 00 08 lwz r30,8(r1)
c003dfc4: 7c 08 03 a6 mtlr r0
c003dfc8: 38 21 00 10 addi r1,r1,16
c003dfcc: 48 05 6f 6c b c0094f38 <trace_event_ignore_this_pid>
c003dfd0: 38 60 00 01 li r3,1
c003dfd4: 4b ff ff ac b c003df80 <trace_trigger_soft_disabled+0x20>
However it is located in a hot path so inlining it is important.
But forcing inlining of the entire function by using __always_inline
leads to increasing the text size by approx 20 kbytes.
Instead, split the fonction in two parts, one part with the likely
fast path, flagged __always_inline, and a second part out of line.
With this change, on a powerpc32 with CONFIG_CC_OPTIMISE_FOR_SIZE
vmlinux text increases by only 1,4 kbytes, which is partly
compensated by a decrease of vmlinux data by 7 kbytes.
On ppc64_defconfig which has CONFIG_CC_OPTIMISE_FOR_SPEED, this
change reduces vmlinux text by more than 30 kbytes.
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
v2: Keep the likely path inline and force it.
---
include/linux/trace_events.h | 22 ++++++++++++----------
kernel/trace/trace_events_trigger.c | 14 ++++++++++++++
2 files changed, 26 insertions(+), 10 deletions(-)
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 70c069aef02c..dcea51fb60e2 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -699,6 +699,8 @@ event_triggers_post_call(struct trace_event_file *file,
bool trace_event_ignore_this_pid(struct trace_event_file *trace_file);
+bool __trace_trigger_soft_disabled(struct trace_event_file *file);
+
/**
* trace_trigger_soft_disabled - do triggers and test if soft disabled
* @file: The file pointer of the event to test
@@ -708,20 +710,20 @@ bool trace_event_ignore_this_pid(struct trace_event_file *trace_file);
* triggers that require testing the fields, it will return true,
* otherwise false.
*/
-static inline bool
+static __always_inline bool
trace_trigger_soft_disabled(struct trace_event_file *file)
{
unsigned long eflags = file->flags;
- if (!(eflags & EVENT_FILE_FL_TRIGGER_COND)) {
- if (eflags & EVENT_FILE_FL_TRIGGER_MODE)
- event_triggers_call(file, NULL, NULL, NULL);
- if (eflags & EVENT_FILE_FL_SOFT_DISABLED)
- return true;
- if (eflags & EVENT_FILE_FL_PID_FILTER)
- return trace_event_ignore_this_pid(file);
- }
- return false;
+ if (likely(!(eflags & (EVENT_FILE_FL_TRIGGER_MODE |
+ EVENT_FILE_FL_SOFT_DISABLED |
+ EVENT_FILE_FL_PID_FILTER))))
+ return false;
+
+ if (likely(eflags & EVENT_FILE_FL_TRIGGER_COND))
+ return false;
+
+ return __trace_trigger_soft_disabled(file);
}
#ifdef CONFIG_BPF_EVENTS
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index d00fee705f9c..55de490e25ca 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -84,6 +84,20 @@ event_triggers_call(struct trace_event_file *file,
}
EXPORT_SYMBOL_GPL(event_triggers_call);
+bool __trace_trigger_soft_disabled(struct trace_event_file *file)
+{
+ unsigned long eflags = file->flags;
+
+ if (eflags & EVENT_FILE_FL_TRIGGER_MODE)
+ event_triggers_call(file, NULL, NULL, NULL);
+ if (eflags & EVENT_FILE_FL_SOFT_DISABLED)
+ return true;
+ if (eflags & EVENT_FILE_FL_PID_FILTER)
+ return trace_event_ignore_this_pid(file);
+ return false;
+}
+EXPORT_SYMBOL_GPL(__trace_trigger_soft_disabled);
+
/**
* event_triggers_post_call - Call 'post_triggers' for a trace event
* @file: The trace_event_file associated with the event
--
2.34.1