powernv: Add OPAL tracepoints
authorAnton Blanchard <anton@samba.org>
Thu, 3 Jul 2014 07:20:50 +0000 (17:20 +1000)
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>
Fri, 11 Jul 2014 06:06:08 +0000 (16:06 +1000)
Knowing how long we spend in firmware calls is an important part of
minimising OS jitter.

This patch adds tracepoints to each OPAL call. If tracepoints are
enabled we branch out to a common routine that calls an entry and exit
tracepoint.

This allows us to write tools that monitor the frequency and duration
of OPAL calls, eg:

name                  count  total(ms)  min(ms)  max(ms)  avg(ms)  period(ms)
OPAL_HANDLE_INTERRUPT     5      0.199    0.037    0.042    0.040   12547.545
OPAL_POLL_EVENTS        204      2.590    0.012    0.036    0.013    2264.899
OPAL_PCI_MSI_EOI       2830      3.066    0.001    0.005    0.001      81.166

We use jump labels if configured, which means we only add a single
nop instruction to every OPAL call when the tracepoints are disabled.

Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
arch/powerpc/include/asm/trace.h
arch/powerpc/platforms/powernv/Makefile
arch/powerpc/platforms/powernv/opal-tracepoints.c [new file with mode: 0644]
arch/powerpc/platforms/powernv/opal-wrappers.S

index 5712f06905a92432ab09959762452ae662c9678f..c15da6073cb8b8e177c715fe81eb76081432d62e 100644 (file)
@@ -99,6 +99,51 @@ TRACE_EVENT_FN(hcall_exit,
 );
 #endif
 
+#ifdef CONFIG_PPC_POWERNV
+extern void opal_tracepoint_regfunc(void);
+extern void opal_tracepoint_unregfunc(void);
+
+TRACE_EVENT_FN(opal_entry,
+
+       TP_PROTO(unsigned long opcode, unsigned long *args),
+
+       TP_ARGS(opcode, args),
+
+       TP_STRUCT__entry(
+               __field(unsigned long, opcode)
+       ),
+
+       TP_fast_assign(
+               __entry->opcode = opcode;
+       ),
+
+       TP_printk("opcode=%lu", __entry->opcode),
+
+       opal_tracepoint_regfunc, opal_tracepoint_unregfunc
+);
+
+TRACE_EVENT_FN(opal_exit,
+
+       TP_PROTO(unsigned long opcode, unsigned long retval),
+
+       TP_ARGS(opcode, retval),
+
+       TP_STRUCT__entry(
+               __field(unsigned long, opcode)
+               __field(unsigned long, retval)
+       ),
+
+       TP_fast_assign(
+               __entry->opcode = opcode;
+               __entry->retval = retval;
+       ),
+
+       TP_printk("opcode=%lu retval=%lu", __entry->opcode, __entry->retval),
+
+       opal_tracepoint_regfunc, opal_tracepoint_unregfunc
+);
+#endif
+
 #endif /* _TRACE_POWERPC_H */
 
 #undef TRACE_INCLUDE_PATH
index 4ad227d04c1ab18a8d1b0eba4fbaab7d1726c795..70b758aaaffa67954a9f3f8ad8248cfccc4bca51 100644 (file)
@@ -8,3 +8,4 @@ obj-$(CONFIG_PCI)       += pci.o pci-p5ioc2.o pci-ioda.o
 obj-$(CONFIG_EEH)      += eeh-ioda.o eeh-powernv.o
 obj-$(CONFIG_PPC_SCOM) += opal-xscom.o
 obj-$(CONFIG_MEMORY_FAILURE)   += opal-memory-errors.o
+obj-$(CONFIG_TRACEPOINTS)      += opal-tracepoints.o
diff --git a/arch/powerpc/platforms/powernv/opal-tracepoints.c b/arch/powerpc/platforms/powernv/opal-tracepoints.c
new file mode 100644 (file)
index 0000000..d8a000a
--- /dev/null
@@ -0,0 +1,84 @@
+#include <linux/percpu.h>
+#include <linux/jump_label.h>
+#include <asm/trace.h>
+
+#ifdef CONFIG_JUMP_LABEL
+struct static_key opal_tracepoint_key = STATIC_KEY_INIT;
+
+void opal_tracepoint_regfunc(void)
+{
+       static_key_slow_inc(&opal_tracepoint_key);
+}
+
+void opal_tracepoint_unregfunc(void)
+{
+       static_key_slow_dec(&opal_tracepoint_key);
+}
+#else
+/*
+ * We optimise OPAL calls by placing opal_tracepoint_refcount
+ * directly in the TOC so we can check if the opal tracepoints are
+ * enabled via a single load.
+ */
+
+/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
+extern long opal_tracepoint_refcount;
+
+void opal_tracepoint_regfunc(void)
+{
+       opal_tracepoint_refcount++;
+}
+
+void opal_tracepoint_unregfunc(void)
+{
+       opal_tracepoint_refcount--;
+}
+#endif
+
+/*
+ * Since the tracing code might execute OPAL calls we need to guard against
+ * recursion.
+ */
+static DEFINE_PER_CPU(unsigned int, opal_trace_depth);
+
+void __trace_opal_entry(unsigned long opcode, unsigned long *args)
+{
+       unsigned long flags;
+       unsigned int *depth;
+
+       local_irq_save(flags);
+
+       depth = &__get_cpu_var(opal_trace_depth);
+
+       if (*depth)
+               goto out;
+
+       (*depth)++;
+       preempt_disable();
+       trace_opal_entry(opcode, args);
+       (*depth)--;
+
+out:
+       local_irq_restore(flags);
+}
+
+void __trace_opal_exit(long opcode, unsigned long retval)
+{
+       unsigned long flags;
+       unsigned int *depth;
+
+       local_irq_save(flags);
+
+       depth = &__get_cpu_var(opal_trace_depth);
+
+       if (*depth)
+               goto out;
+
+       (*depth)++;
+       trace_opal_exit(opcode, retval);
+       preempt_enable();
+       (*depth)--;
+
+out:
+       local_irq_restore(flags);
+}
index 4abbff22a61f0a6165b3d475156c32bb633d6538..27c40bcf9d1260be71042c57ad29c48a82028de5 100644 (file)
 #include <asm/hvcall.h>
 #include <asm/asm-offsets.h>
 #include <asm/opal.h>
+#include <asm/jump_label.h>
+
+       .section        ".text"
+
+#ifdef CONFIG_TRACEPOINTS
+#ifdef CONFIG_JUMP_LABEL
+#define OPAL_BRANCH(LABEL)                                     \
+       ARCH_STATIC_BRANCH(LABEL, opal_tracepoint_key)
+#else
+
+       .section        ".toc","aw"
+
+       .globl opal_tracepoint_refcount
+opal_tracepoint_refcount:
+       .llong  0
+
+       .section        ".text"
+
+/*
+ * We branch around this in early init by using an unconditional cpu
+ * feature.
+ */
+#define OPAL_BRANCH(LABEL)                                     \
+BEGIN_FTR_SECTION;                                             \
+       b       1f;                                             \
+END_FTR_SECTION(0, 1);                                         \
+       ld      r12,opal_tracepoint_refcount@toc(r2);           \
+       std     r12,32(r1);                                     \
+       cmpdi   r12,0;                                          \
+       bne-    LABEL;                                          \
+1:
+
+#endif
+
+#else
+#define OPAL_BRANCH(LABEL)
+#endif
 
 /* TODO:
  *
  * - Trace irqs in/off (needs saving/restoring all args, argh...)
  * - Get r11 feed up by Dave so I can have better register usage
  */
+
 #define OPAL_CALL(name, token)         \
  _GLOBAL(name);                                \
        mflr    r0;                     \
-       mfcr    r12;                    \
        std     r0,16(r1);              \
+       li      r0,token;               \
+       OPAL_BRANCH(opal_tracepoint_entry) \
+       mfcr    r12;                    \
        stw     r12,8(r1);              \
        std     r1,PACAR1(r13);         \
-       li      r0,0;                   \
+       li      r11,0;                  \
        mfmsr   r12;                    \
-       ori     r0,r0,MSR_EE;           \
+       ori     r11,r11,MSR_EE;         \
        std     r12,PACASAVEDMSR(r13);  \
-       andc    r12,r12,r0;             \
+       andc    r12,r12,r11;            \
        mtmsrd  r12,1;                  \
-       LOAD_REG_ADDR(r0,opal_return);  \
-       mtlr    r0;                     \
-       li      r0,MSR_DR|MSR_IR|MSR_LE;\
-       andc    r12,r12,r0;             \
-       li      r0,token;               \
+       LOAD_REG_ADDR(r11,opal_return); \
+       mtlr    r11;                    \
+       li      r11,MSR_DR|MSR_IR|MSR_LE;\
+       andc    r12,r12,r11;            \
        mtspr   SPRN_HSRR1,r12;         \
        LOAD_REG_ADDR(r11,opal);        \
        ld      r12,8(r11);             \
@@ -61,6 +100,64 @@ opal_return:
        mtcr    r4;
        rfid
 
+#ifdef CONFIG_TRACEPOINTS
+opal_tracepoint_entry:
+       stdu    r1,-STACKFRAMESIZE(r1)
+       std     r0,STK_REG(R23)(r1)
+       std     r3,STK_REG(R24)(r1)
+       std     r4,STK_REG(R25)(r1)
+       std     r5,STK_REG(R26)(r1)
+       std     r6,STK_REG(R27)(r1)
+       std     r7,STK_REG(R28)(r1)
+       std     r8,STK_REG(R29)(r1)
+       std     r9,STK_REG(R30)(r1)
+       std     r10,STK_REG(R31)(r1)
+       mr      r3,r0
+       addi    r4,r1,STK_REG(R24)
+       bl      __trace_opal_entry
+       ld      r0,STK_REG(R23)(r1)
+       ld      r3,STK_REG(R24)(r1)
+       ld      r4,STK_REG(R25)(r1)
+       ld      r5,STK_REG(R26)(r1)
+       ld      r6,STK_REG(R27)(r1)
+       ld      r7,STK_REG(R28)(r1)
+       ld      r8,STK_REG(R29)(r1)
+       ld      r9,STK_REG(R30)(r1)
+       ld      r10,STK_REG(R31)(r1)
+       LOAD_REG_ADDR(r11,opal_tracepoint_return)
+       mfcr    r12
+       std     r11,16(r1)
+       stw     r12,8(r1)
+       std     r1,PACAR1(r13)
+       li      r11,0
+       mfmsr   r12
+       ori     r11,r11,MSR_EE
+       std     r12,PACASAVEDMSR(r13)
+       andc    r12,r12,r11
+       mtmsrd  r12,1
+       LOAD_REG_ADDR(r11,opal_return)
+       mtlr    r11
+       li      r11,MSR_DR|MSR_IR|MSR_LE
+       andc    r12,r12,r11
+       mtspr   SPRN_HSRR1,r12
+       LOAD_REG_ADDR(r11,opal)
+       ld      r12,8(r11)
+       ld      r2,0(r11)
+       mtspr   SPRN_HSRR0,r12
+       hrfid
+
+opal_tracepoint_return:
+       std     r3,STK_REG(R31)(r1)
+       mr      r4,r3
+       ld      r0,STK_REG(R23)(r1)
+       bl      __trace_opal_exit
+       ld      r3,STK_REG(R31)(r1)
+       addi    r1,r1,STACKFRAMESIZE
+       ld      r0,16(r1)
+       mtlr    r0
+       blr
+#endif
+
 OPAL_CALL(opal_invalid_call,                   OPAL_INVALID_CALL);
 OPAL_CALL(opal_console_write,                  OPAL_CONSOLE_WRITE);
 OPAL_CALL(opal_console_read,                   OPAL_CONSOLE_READ);