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Date: Mon, 20 Jul 2009 13:08:07 -0400
From: Frederic Weisbecker <fweisbec@...il.com>
To: Ingo Molnar <mingo@...e.hu>
Cc: LKML <linux-kernel@...r.kernel.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...uxtronix.de>,
Mike Galbraith <efault@....de>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Paul Mackerras <paulus@...ba.org>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
Lai Jiangshan <laijs@...fujitsu.com>,
Anton Blanchard <anton@...ba.org>,
Li Zefan <lizf@...fujitsu.com>,
Zhaolei <zhaolei@...fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
"K . Prasad" <prasad@...ux.vnet.ibm.com>,
Alan Stern <stern@...land.harvard.edu>
Subject: [RFC][PATCH 5/5] perfcounter: Add support for kernel hardware breakpoints
This adds the support for kernel hardware breakpoints in perfcounter.
It is added as a new type of software counter and can be defined by
using the counter number 5 and by passsing the address of the
breakpoint to set through the config attribute.
Example which traces the BKL accesses by stressing reiserfs:
bkl=0x$(cat ../../System.map | grep kernel_flag | cut -d" " -f 1)
./perf record -f -g -e 5:$bkl -- dbench -t 20 20
./perf report -g -s s
# Samples: 36
#
# Overhead Symbol
# ........ ......
#
83.33% [k] lock_kernel
|
|--51.72%-- __pwrite64
|
|--27.59%-- 0x7f9d83a17b15
|
|--13.79%-- __open
|
--10.34%-- unlink
16.67% [k] unlock_kernel
|
|--80.00%-- 0x7f9d83a17b15
|
|--20.00%-- unlink
|
--20.00%-- __pwrite64
For now you can only pass raw kernel addresses.
What is planned next:
- profile by symbol names
- profile with user breakpoints
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Mike Galbraith <efault@....de>
Cc: Thomas Gleixner <tglx@...uxtronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Anton Blanchard <anton@...ba.org>
Cc: K.Prasad <prasad@...ux.vnet.ibm.com>
Cc: Alan Stern <stern@...land.harvard.edu>
Cc: Steven Rostedt <rostedt@...dmis.org>
---
include/asm-generic/hw_breakpoint.h | 4 ++
include/linux/perf_counter.h | 1 +
kernel/hw_breakpoint.c | 79 +++++++++++++++++++++++++++++++++++
kernel/perf_counter.c | 35 +++++++++++++++
4 files changed, 119 insertions(+), 0 deletions(-)
diff --git a/include/asm-generic/hw_breakpoint.h b/include/asm-generic/hw_breakpoint.h
index 598e3c4..82657bb 100644
--- a/include/asm-generic/hw_breakpoint.h
+++ b/include/asm-generic/hw_breakpoint.h
@@ -105,6 +105,10 @@ register_kernel_hw_breakpoint(struct hw_breakpoint *bp, unsigned long addr,
int len, enum breakpoint_type type);
extern void unregister_kernel_hw_breakpoint(struct hw_breakpoint *bp);
+#ifdef CONFIG_PERF_COUNTERS
+extern void bp_perf_triggered(struct hw_breakpoint *bp, struct pt_regs *regs);
+#endif
+
extern unsigned int hbp_kernel_pos;
#endif /* __KERNEL__ */
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 5e970c7..c97df54 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -31,6 +31,7 @@ enum perf_type_id {
PERF_TYPE_TRACEPOINT = 2,
PERF_TYPE_HW_CACHE = 3,
PERF_TYPE_RAW = 4,
+ PERF_TYPE_BREAKPOINT = 5,
PERF_TYPE_MAX, /* non-ABI */
};
diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
index f9e62e7..c22c29d 100644
--- a/kernel/hw_breakpoint.c
+++ b/kernel/hw_breakpoint.c
@@ -72,6 +72,85 @@ unsigned int hbp_kernel_pos = HBP_NUM;
*/
unsigned int hbp_user_refcount[HBP_NUM];
+struct bp_perf_event {
+ struct hw_breakpoint *bp;
+ int count;
+ struct list_head list;
+};
+
+#ifdef CONFIG_PERF_COUNTERS
+
+static LIST_HEAD(breakpoint_perf_events);
+static DEFINE_MUTEX(breakpoint_perf_lock);
+
+
+int hw_breakpoint_perf_init(unsigned long addr)
+{
+ struct bp_perf_event *event;
+ int ret;
+
+ mutex_lock(&breakpoint_perf_lock);
+
+ list_for_each_entry(event, &breakpoint_perf_events, list) {
+ if (hw_breakpoint_addr(event->bp) == addr) {
+ event->count++;
+ goto found;
+ }
+ }
+
+ mutex_unlock(&breakpoint_perf_lock);
+
+ event = kzalloc(sizeof(*event), GFP_KERNEL);
+ if (!event)
+ return -ENOMEM;
+
+ event->bp = kzalloc(sizeof(*event->bp), GFP_KERNEL);
+ if (!event->bp) {
+ ret = -ENOMEM;
+ goto fail;
+ }
+
+ event->bp->triggered = bp_perf_triggered;
+ ret = register_kernel_hw_breakpoint(event->bp, addr, 1,
+ BREAK_RW);
+ if (ret)
+ goto fail;
+
+ mutex_lock(&breakpoint_perf_lock);
+ list_add_tail(&event->list, &breakpoint_perf_events);
+
+found:
+ mutex_unlock(&breakpoint_perf_lock);
+ return 0;
+
+fail:
+ kfree(event->bp);
+ kfree(event);
+ return ret;
+}
+
+void hw_breakpoint_perf_exit(unsigned long addr)
+{
+ struct bp_perf_event *event;
+
+ mutex_lock(&breakpoint_perf_lock);
+
+ list_for_each_entry(event, &breakpoint_perf_events, list) {
+ if (hw_breakpoint_addr(event->bp) == addr) {
+ if (--event->count)
+ break;
+
+ list_del(&event->list);
+ unregister_kernel_hw_breakpoint(event->bp);
+ kfree(event->bp);
+ kfree(event);
+ break;
+ }
+ }
+ mutex_unlock(&breakpoint_perf_lock);
+}
+#endif
+
/*
* Load the debug registers during startup of a CPU.
*/
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 33ffb5a..8c70723 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -29,6 +29,7 @@
#include <linux/perf_counter.h>
#include <asm/irq_regs.h>
+#include <asm/hw_breakpoint.h>
/*
* Each CPU has a list of per CPU counters:
@@ -3718,6 +3719,36 @@ static const struct pmu *tp_perf_counter_init(struct perf_counter *counter)
}
#endif
+extern int hw_breakpoint_perf_init(unsigned long addr);
+extern void hw_breakpoint_perf_exit(unsigned long addr);
+
+void bp_perf_triggered(struct hw_breakpoint *bp, struct pt_regs *regs)
+{
+ unsigned long target = hw_breakpoint_addr(bp);
+
+ struct perf_sample_data data = {
+ .regs = regs,
+ .addr = instruction_pointer(regs),
+ };
+
+ do_perf_swcounter_event(PERF_TYPE_BREAKPOINT, target, 1, 0, &data);
+}
+
+static void bp_perf_counter_destroy(struct perf_counter *counter)
+{
+ hw_breakpoint_perf_exit(counter->attr.config);
+}
+
+static const struct pmu *bp_perf_counter_init(struct perf_counter *counter)
+{
+ if (hw_breakpoint_perf_init((unsigned long)counter->attr.config))
+ return NULL;
+
+ counter->destroy = bp_perf_counter_destroy;
+
+ return &perf_ops_generic;
+}
+
atomic_t perf_swcounter_enabled[PERF_COUNT_SW_MAX];
static void sw_perf_counter_destroy(struct perf_counter *counter)
@@ -3857,6 +3888,10 @@ perf_counter_alloc(struct perf_counter_attr *attr,
pmu = tp_perf_counter_init(counter);
break;
+ case PERF_TYPE_BREAKPOINT:
+ pmu = bp_perf_counter_init(counter);
+ break;
+
default:
break;
}
--
1.6.2.3
--
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