Enable perf-events to collect memory access statistics on kernel-space
data in the context of a running process.
Signed-off-by: K.Prasad <[email protected]>
---
include/linux/perf_event.h | 18 ++++++
kernel/perf_event.c | 108 ++++++++++++++++++++++++++++++++++++++++-
tools/perf/util/parse-events.c | 47 +++++++++++++++++
3 files changed, 172 insertions(+), 1 deletion(-)
Index: linux-2.6-tip.perf_hbkpt/include/linux/perf_event.h
===================================================================
--- linux-2.6-tip.perf_hbkpt.orig/include/linux/perf_event.h
+++ linux-2.6-tip.perf_hbkpt/include/linux/perf_event.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 */
};
@@ -106,6 +107,14 @@ enum perf_sw_ids {
PERF_COUNT_SW_MAX, /* non-ABI */
};
+/* Various breakpoint types for monitoring accesses over variables */
+enum perf_bp_id {
+ PERF_COUNT_BP_WRITE = 0,
+ PERF_COUNT_BP_RW = 1,
+
+ PERF_COUNT_BP_MAX, /* non-ABI */
+};
+
/*
* Bits that can be set in attr.sample_type to request information
* in the overflow packets.
@@ -207,6 +216,11 @@ struct perf_event_attr {
__u32 wakeup_events; /* wakeup every n events */
__u32 wakeup_watermark; /* bytes before wakeup */
};
+
+ /* Store the symbol name for breakpoint request */
+ /* TODO: ksym_name[KSYM_NAME_LEN] requires kallsyms.h to be included */
+ char ksym_name[128];
+
__u32 __reserved_2;
__u64 __reserved_3;
@@ -476,6 +490,10 @@ struct hw_perf_event {
s64 remaining;
struct hrtimer hrtimer;
};
+ struct { /* hardware breakpoints */
+ struct hw_breakpoint *bp;
+ int counter;
+ };
};
atomic64_t prev_count;
u64 sample_period;
Index: linux-2.6-tip.perf_hbkpt/kernel/perf_event.c
===================================================================
--- linux-2.6-tip.perf_hbkpt.orig/kernel/perf_event.c
+++ linux-2.6-tip.perf_hbkpt/kernel/perf_event.c
@@ -4,7 +4,7 @@
* Copyright (C) 2008 Thomas Gleixner <[email protected]>
* Copyright (C) 2008-2009 Red Hat, Inc., Ingo Molnar
* Copyright (C) 2008-2009 Red Hat, Inc., Peter Zijlstra <[email protected]>
- * Copyright ? 2009 Paul Mackerras, IBM Corp. <[email protected]>
+ * Copyright � 2009 Paul Mackerras, IBM Corp. <[email protected]>
*
* For licensing details see kernel-base/COPYING
*/
@@ -31,6 +31,7 @@
#include <linux/ftrace_event.h>
#include <asm/irq_regs.h>
+#include <asm/hw_breakpoint.h>
/*
* Each CPU has a list of per CPU events:
@@ -4124,6 +4125,27 @@ static const struct pmu perf_ops_task_cl
.read = task_clock_perf_event_read,
};
+static int hw_breakpoint_perf_event_enable(struct perf_event *event)
+{
+ enable_hw_breakpoint(event->hw.bp);
+ return 0;
+}
+
+static void hw_breakpoint_perf_event_disable(struct perf_event *event)
+{
+ disable_hw_breakpoint(event->hw.bp);
+}
+
+static void hw_breakpoint_perf_event_read(struct perf_event *event)
+{
+}
+
+static const struct pmu perf_ops_hw_breakpoint = {
+ .enable = hw_breakpoint_perf_event_enable,
+ .disable = hw_breakpoint_perf_event_disable,
+ .read = hw_breakpoint_perf_event_read,
+};
+
#ifdef CONFIG_EVENT_PROFILE
void perf_tp_event(int event_id, u64 addr, u64 count, void *record,
@@ -4285,6 +4307,86 @@ static const struct pmu *sw_perf_event_i
return pmu;
}
+static void perf_hw_breakpoint_handler(struct hw_breakpoint *bp,
+ struct pt_regs *regs)
+{
+ int event_id = 0;
+ struct perf_sample_data data = {
+ .addr = bp->info.address,
+ };
+
+ switch (bp->info.type) {
+ case HW_BREAKPOINT_WRITE:
+ event_id = PERF_COUNT_BP_WRITE;
+ break;
+
+ case HW_BREAKPOINT_RW:
+ event_id = PERF_COUNT_BP_RW;
+ break;
+
+ default:
+ return;
+ }
+
+ do_perf_sw_event(PERF_TYPE_BREAKPOINT, event_id, 1, 1,
+ &data, regs);
+}
+
+static void hw_breakpoint_perf_event_destroy(struct perf_event *event)
+{
+ struct hw_breakpoint *bp = event->hw.bp;
+
+ unregister_kernel_hw_breakpoint(bp);
+ kfree(bp);
+}
+
+static const struct pmu *hw_breakpoint_perf_event_init(struct perf_event *event,
+ int cpu, gfp_t gfpflags)
+{
+ int ret;
+ struct perf_event_attr *attr = &event->attr;
+ u64 event_id = attr->config;
+ struct hw_breakpoint *bp;
+
+ bp = event->hw.bp = kzalloc(sizeof(struct hw_breakpoint), gfpflags);
+ if (!bp)
+ return ERR_PTR(-ENOMEM);
+
+ switch (event_id) {
+
+ case PERF_COUNT_BP_WRITE:
+ bp->info.type = HW_BREAKPOINT_WRITE;
+ break;
+ case PERF_COUNT_BP_RW:
+ bp->info.type = HW_BREAKPOINT_RW;
+ break;
+ default:
+ return ERR_PTR(-EINVAL);
+ }
+ /*
+ * Ideally we should determine the size of the kernel-symbol and request
+ * for corresponding breakpoint length. But since the lengths are encoded,
+ * we will request for a 1-Byte length breakpoint to be placed at the start.
+ */
+ bp->info.len = HW_BREAKPOINT_LEN_1;
+ bp->triggered = perf_hw_breakpoint_handler;
+
+ if (attr->ksym_name)
+ bp->info.name = attr->ksym_name;
+ else
+ return ERR_PTR(-EINVAL);
+
+ if (cpu != -1)
+ bp->cpumask = cpumask_of(cpu);
+
+ ret = register_kernel_hw_breakpoint(bp);
+ if (ret)
+ return ERR_PTR(ret);
+
+ event->destroy = hw_breakpoint_perf_event_destroy;
+ return &perf_ops_hw_breakpoint;
+}
+
/*
* Allocate and initialize a event structure
*/
@@ -4370,6 +4472,10 @@ perf_event_alloc(struct perf_event_attr
pmu = tp_perf_event_init(event);
break;
+ case PERF_TYPE_BREAKPOINT:
+ pmu = hw_breakpoint_perf_event_init(event, cpu, gfpflags);
+ break;
+
default:
break;
}
Index: linux-2.6-tip.perf_hbkpt/tools/perf/util/parse-events.c
===================================================================
--- linux-2.6-tip.perf_hbkpt.orig/tools/perf/util/parse-events.c
+++ linux-2.6-tip.perf_hbkpt/tools/perf/util/parse-events.c
@@ -30,6 +30,7 @@ char debugfs_path[MAXPATHLEN];
#define CHW(x) .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_##x
#define CSW(x) .type = PERF_TYPE_SOFTWARE, .config = PERF_COUNT_SW_##x
+#define CHBP(x) .type = PERF_TYPE_BREAKPOINT, .config = PERF_COUNT_BP_##x
static struct event_symbol event_symbols[] = {
{ CHW(CPU_CYCLES), "cpu-cycles", "cycles" },
@@ -47,6 +48,13 @@ static struct event_symbol event_symbols
{ CSW(PAGE_FAULTS_MAJ), "major-faults", "" },
{ CSW(CONTEXT_SWITCHES), "context-switches", "cs" },
{ CSW(CPU_MIGRATIONS), "cpu-migrations", "migrations" },
+
+ /*
+ * Allow the hw-breakpoint events to be the last two elements for a small
+ * optimisation used in parse_hbp_event().
+ */
+ { CHBP(WRITE), "memory-write", "w" },
+ { CHBP(RW), "memory-readwrite", "rw" },
};
#define __PERF_EVENT_FIELD(config, name) \
@@ -77,6 +85,11 @@ static const char *sw_event_names[] = {
"major-faults",
};
+static const char *hbp_event_names[] = {
+ "memory-write",
+ "memory-readwrite",
+};
+
#define MAX_ALIASES 8
static const char *hw_cache[][MAX_ALIASES] = {
@@ -322,6 +335,9 @@ const char *__event_name(int type, u64 c
case PERF_TYPE_TRACEPOINT:
return tracepoint_id_to_name(config);
+ case PERF_TYPE_BREAKPOINT:
+ return hbp_event_names[config];
+
default:
break;
}
@@ -621,6 +637,32 @@ parse_numeric_event(const char **strp, s
}
static enum event_result
+parse_hbp_event(const char **strp, struct perf_event_attr *attr)
+{
+ unsigned int i, j, n;
+
+ char *bp_data = (char *)(*strp);
+ char *bp_event_name = strsep(&bp_data, ":");
+
+ /* bp_data will turn NULL if ":" was not present in the event string */
+ if (!bp_data)
+ return EVT_FAILED;
+
+ for (i = (ARRAY_SIZE(event_symbols) - PERF_COUNT_BP_MAX), j = 0;
+ i < ARRAY_SIZE(event_symbols); i++, j++) {
+ n = check_events(bp_event_name, i);
+ if (!n)
+ continue;
+ attr->config = j;
+ attr->type = PERF_TYPE_BREAKPOINT;
+ strcpy(attr->ksym_name, bp_data);
+ *strp = (*strp) + strlen(*strp) + strlen(bp_data) + 1;
+ return EVT_HANDLED;
+ }
+ return EVT_FAILED;
+}
+
+static enum event_result
parse_event_modifier(const char **strp, struct perf_event_attr *attr)
{
const char *str = *strp;
@@ -658,6 +700,10 @@ parse_event_symbols(const char **str, st
{
enum event_result ret;
+ ret = parse_hbp_event(str, attr);
+ if (ret != EVT_FAILED)
+ goto modifier;
+
ret = parse_tracepoint_event(str, attr);
if (ret != EVT_FAILED)
goto modifier;
@@ -773,6 +819,7 @@ static const char * const event_type_des
"Software event",
"Tracepoint event",
"Hardware cache event",
+ "Memory access event",
};
/*
On Fri, Oct 30, 2009 at 03:52:23AM +0530, K.Prasad wrote:
> Enable perf-events to collect memory access statistics on kernel-space
> data in the context of a running process.
>
> Signed-off-by: K.Prasad <[email protected]>
I'm going to take the userspace part of this patch to integrate breakpoints
in perf tools.
But I'm not sure passing the name of the symbol to the kernel and store
it in the perf attr is a good idea.
We should probably resolve the name from userspace and pass the address
to the kernel. Mostly because if we want to support breakpoints in
userspace apps, we don't want conflicts between kernel and userspace
symbols.
Thanks.
On Sun, Nov 22, 2009 at 03:52:00AM +0100, Frederic Weisbecker wrote:
> On Fri, Oct 30, 2009 at 03:52:23AM +0530, K.Prasad wrote:
> > Enable perf-events to collect memory access statistics on kernel-space
> > data in the context of a running process.
> >
> > Signed-off-by: K.Prasad <[email protected]>
>
>
>
> I'm going to take the userspace part of this patch to integrate breakpoints
> in perf tools.
>
> But I'm not sure passing the name of the symbol to the kernel and store
> it in the perf attr is a good idea.
> We should probably resolve the name from userspace and pass the address
> to the kernel. Mostly because if we want to support breakpoints in
> userspace apps, we don't want conflicts between kernel and userspace
> symbols.
>
> Thanks.
>
Hmm, actually instead of memory-write/memory-readwrite
I would rather see:
mem:symbol:[r][w][x]
like mem:pid_max:rw
We could default it to rw for now.
This will be more flexible I guess.
And later for ranges:
mem:symbol[[start]:[len]:[rwx]
This could be:
mem:array_name[0:5]:rwx
So, I'll need an ad-hoc parsing function for this one. This
would be hard by integrating your patch.
I'll try something else. But I can probably take the 5th patch
of your series.
Thanks.