[RFC][PATCH 0/3] more perf_counter stuff

[RFC][PATCH 0/3] more perf_counter stuff

[Peter Zijlstra]

mostly compile tested.. :-)

-- 

[RFC][PATCH 1/3] perf_counter: event overlow handling

[Peter Zijlstra]

[-- Attachment #1: perf_counter-mmap-write.patch --]
[-- Type: text/plain, Size: 5009 bytes --]

Alternative method of mmap() data output handling that provides better
overflow management.

Unlike the previous method, that didn't have any user->kernel
feedback and relied on userspace keeping up, this method relies on
userspace writing its last read position into the control page. 

It will ensure new output doesn't overwrite not-yet read events, new
events for which there is no space left are lost and the overflow
counter is incremented, providing exact event loss numbers.

Untested -- not sure its really worth the overhead, the most important
thing to know is _if_ you're loosing data, either method allows for
that.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 include/linux/perf_counter.h |    4 ++
 kernel/perf_counter.c        |   69 ++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 66 insertions(+), 7 deletions(-)

Index: linux-2.6/include/linux/perf_counter.h
===================================================================
--- linux-2.6.orig/include/linux/perf_counter.h
+++ linux-2.6/include/linux/perf_counter.h
@@ -165,6 +165,8 @@ struct perf_counter_mmap_page {
 	__s64	offset;			/* add to hardware counter value */
 
 	__u32   data_head;		/* head in the data section */
+	__u32	data_tail;		/* user-space written tail */
+	__u32	overflow;		/* number of lost events */
 };
 
 struct perf_event_header {
@@ -269,8 +271,10 @@ struct file;
 struct perf_mmap_data {
 	struct rcu_head			rcu_head;
 	int				nr_pages;
+	int				writable;
 	atomic_t			wakeup;
 	atomic_t			head;
+	atomic_t			overflow;
 	struct perf_counter_mmap_page   *user_page;
 	void 				*data_pages[0];
 };
Index: linux-2.6/kernel/perf_counter.c
===================================================================
--- linux-2.6.orig/kernel/perf_counter.c
+++ linux-2.6/kernel/perf_counter.c
@@ -1330,6 +1330,7 @@ static void __perf_counter_update_userpa
 		userpg->offset -= atomic64_read(&counter->hw.prev_count);
 
 	userpg->data_head = atomic_read(&data->head);
+	userpg->overflow = atomic_read(&data->overflow);
 	smp_wmb();
 	++userpg->lock;
 	preempt_enable();
@@ -1375,6 +1376,30 @@ unlock:
 	return ret;
 }
 
+static int perf_mmap_mkwrite(struct vm_area_struct *vma, struct page *page)
+{
+	struct perf_counter *counter = vma->vm_file->private_data;
+	struct perf_mmap_data *data;
+	int ret = -EINVAL;
+
+	rcu_read_lock();
+	data = rcu_dereference(counter->data);
+	if (!data)
+		goto unlock;
+
+	/*
+	 * Only allow writes to the control page.
+	 */
+	if (page != virt_to_page(data->user_page))
+		goto unlock;
+
+	ret = 0;
+unlock:
+	rcu_read_unlock();
+
+	return ret;
+}
+
 static int perf_mmap_data_alloc(struct perf_counter *counter, int nr_pages)
 {
 	struct perf_mmap_data *data;
@@ -1463,6 +1488,7 @@ static struct vm_operations_struct perf_
 	.open = perf_mmap_open,
 	.close = perf_mmap_close,
 	.fault = perf_mmap_fault,
+	.page_mkwrite = perf_mmap_mkwrite,
 };
 
 static int perf_mmap(struct file *file, struct vm_area_struct *vma)
@@ -1473,7 +1499,7 @@ static int perf_mmap(struct file *file, 
 	unsigned long locked, lock_limit;
 	int ret = 0;
 
-	if (!(vma->vm_flags & VM_SHARED) || (vma->vm_flags & VM_WRITE))
+	if (!(vma->vm_flags & VM_SHARED))
 		return -EINVAL;
 
 	vma_size = vma->vm_end - vma->vm_start;
@@ -1503,16 +1529,19 @@ static int perf_mmap(struct file *file, 
 
 	mutex_lock(&counter->mmap_mutex);
 	if (atomic_inc_not_zero(&counter->mmap_count))
-		goto out;
+		goto unlock;
 
 	WARN_ON(counter->data);
 	ret = perf_mmap_data_alloc(counter, nr_pages);
-	if (!ret)
-		atomic_set(&counter->mmap_count, 1);
-out:
+	if (ret)
+		goto unlock;
+
+	atomic_set(&counter->mmap_count, 1);
+	if (vma->vm_flags & VM_WRITE)
+		counter->data->writable = 1;
+unlock:
 	mutex_unlock(&counter->mmap_mutex);
 
-	vma->vm_flags &= ~VM_MAYWRITE;
 	vma->vm_flags |= VM_RESERVED;
 	vma->vm_ops = &perf_mmap_vmops;
 
@@ -1540,6 +1569,28 @@ struct perf_output_handle {
 	int			wakeup;
 };
 
+static int perf_output_overflow(struct perf_mmap_data *data,
+				unsigned int offset, unsigned int head)
+{
+	unsigned int tail;
+	unsigned int mask;
+
+	if (!data->writable)
+		return 0;
+
+	mask = (data->nr_pages << PAGE_SHIFT) - 1;
+	smp_rmb();
+	tail = ACCESS_ONCE(data->user_page->data_tail);
+
+	offset = (offset - tail) & mask;
+	head   = (head   - tail) & mask;
+
+	if ((int)(head - offset) < 0)
+		return 1;
+
+	return 0;
+}
+
 static int perf_output_begin(struct perf_output_handle *handle,
 			     struct perf_counter *counter, unsigned int size)
 {
@@ -1552,11 +1603,13 @@ static int perf_output_begin(struct perf
 		goto out;
 
 	if (!data->nr_pages)
-		goto out;
+		goto fail;
 
 	do {
 		offset = head = atomic_read(&data->head);
 		head += size;
+		if (unlikely(perf_output_overflow(data, offset, head)))
+			goto fail;
 	} while (atomic_cmpxchg(&data->head, offset, head) != offset);
 
 	handle->counter	= counter;
@@ -1567,6 +1620,8 @@ static int perf_output_begin(struct perf
 
 	return 0;
 
+fail:
+	atomic_inc(&data->overflow);
 out:
 	rcu_read_unlock();
 

-- 

[RFC][PATCH 2/3] perf_counter: executable mmap() information

[Peter Zijlstra]

[-- Attachment #1: perf_counter-mmap-tracking.patch --]
[-- Type: text/plain, Size: 7096 bytes --]

Currently the profiling information returns userspace IPs but now way
to correlate them to userspace code. Userspace could look into
/proc/$pid/maps but that might not be current or even present anymore
at the time of analyzing the IPs.

Therefore provide means to track the mmap information and provide it
in the output stream.

XXX: only covers mmap()/munmap(), mremap() and mprotect() are missing.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 include/linux/perf_counter.h |   22 ++++++-
 kernel/perf_counter.c        |  135 +++++++++++++++++++++++++++++++++++++++++++
 mm/mmap.c                    |   10 +++
 3 files changed, 166 insertions(+), 1 deletion(-)

Index: linux-2.6/include/linux/perf_counter.h
===================================================================
--- linux-2.6.orig/include/linux/perf_counter.h
+++ linux-2.6/include/linux/perf_counter.h
@@ -137,7 +137,9 @@ struct perf_counter_hw_event {
 				exclude_kernel :  1, /* ditto kernel          */
 				exclude_hv     :  1, /* ditto hypervisor      */
 				exclude_idle   :  1, /* don't count when idle */
-				include_tid    :  1, /* include the tid */
+				include_tid    :  1, /* include the tid       */
+				mmap           :  1, /* include mmap data     */
+				munmap         :  1, /* include munmap data   */
 
 				__reserved_1   : 54;
 
@@ -178,6 +180,9 @@ enum perf_event_type {
 	PERF_EVENT_IP		= 0,
 	PERF_EVENT_GROUP	= 1,
 
+	PERF_EVENT_MMAP		= 2,
+	PERF_EVENT_MUNMAP	= 3,
+
 	__PERF_EVENT_TID	= 0x100,
 };
 
@@ -456,6 +461,12 @@ static inline int is_software_counter(st
 
 extern void perf_swcounter_event(u32, u64, int, struct pt_regs *);
 
+extern void perf_counter_mmap(unsigned long addr, unsigned long len,
+			      unsigned long pgoff, struct file *file);
+
+extern void perf_counter_munmap(unsigned long addr, unsigned long len,
+				unsigned long pgoff, struct file *file);
+
 #else
 static inline void
 perf_counter_task_sched_in(struct task_struct *task, int cpu)		{ }
@@ -475,6 +486,15 @@ static inline int perf_counter_task_enab
 
 static inline void perf_swcounter_event(u32 event, u64 nr,
 					int nmi, struct pt_regs *regs)	{ }
+
+static inline void perf_counter_mmap(unsigned long addr, unsigned long len,
+				     unsigned long pgoff, struct file *file)
+{ }
+
+static inline void perf_counter_munmap(unsigned long addr, unsigned long len,
+				       unsigned long pgoff, struct file *file)
+{ }
+
 #endif
 
 #endif /* __KERNEL__ */
Index: linux-2.6/kernel/perf_counter.c
===================================================================
--- linux-2.6.orig/kernel/perf_counter.c
+++ linux-2.6/kernel/perf_counter.c
@@ -25,6 +25,7 @@
 #include <linux/anon_inodes.h>
 #include <linux/kernel_stat.h>
 #include <linux/perf_counter.h>
+#include <linux/dcache.h>
 
 #include <asm/irq_regs.h>
 
@@ -1778,6 +1779,140 @@ void perf_counter_output(struct perf_cou
 }
 
 /*
+ * mmap tracking
+ */
+
+struct perf_mmap_event {
+	struct file	*file;
+	char		*file_name;
+	int		file_size;
+
+	struct {
+		struct perf_event_header	header;
+
+		u32				pid;
+		u32				tid;
+		u64				start;
+		u64				len;
+		u64				pgoff;
+	} event;
+};
+
+static void perf_counter_mmap_output(struct perf_counter *counter,
+				     struct perf_mmap_event *mmap_event)
+{
+	struct perf_output_handle handle;
+	int size = mmap_event->event.header.size;
+	int ret = perf_output_begin(&handle, counter, size);
+
+	if (ret)
+		return;
+
+	perf_output_put(&handle, mmap_event->event);
+	perf_output_copy(&handle, mmap_event->file_name,
+				   mmap_event->file_size);
+	perf_output_end(&handle, 0);
+}
+
+static int perf_counter_mmap_match(struct perf_counter *counter,
+				   struct perf_mmap_event *mmap_event)
+{
+	if (counter->hw_event.mmap &&
+	    mmap_event->event.header.type == PERF_EVENT_MMAP)
+		return 1;
+
+	if (counter->hw_event.munmap &&
+	    mmap_event->event.header.type == PERF_EVENT_MUNMAP)
+		return 1;
+
+	return 0;
+}
+
+static void perf_counter_mmap_ctx(struct perf_counter_context *ctx,
+				  struct perf_mmap_event *mmap_event)
+{
+	struct perf_counter *counter;
+
+	if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
+		return;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(counter, &ctx->event_list, event_entry) {
+		if (perf_counter_mmap_match(counter, mmap_event))
+			perf_counter_mmap_output(counter, mmap_event);
+	}
+	rcu_read_unlock();
+}
+
+static void perf_counter_mmap_event(struct perf_mmap_event *mmap_event)
+{
+	struct perf_cpu_context *cpuctx;
+	struct file *file = mmap_event->file;
+	unsigned int size;
+	char *buf = NULL;
+	char *name;
+
+	if (file) {
+		name = kzalloc(PATH_MAX, GFP_KERNEL);
+		name = dentry_path(file->f_dentry, name, PATH_MAX);
+		if (IS_ERR(name))
+			name = "//toolong\0\0\0\0\0\0\0";
+	} else
+		name = "//anon\0\0";
+
+	size = ALIGN(strlen(name), sizeof(u64));
+
+	mmap_event->file_name = name;
+	mmap_event->file_size = size;
+
+	mmap_event->event.header.size = sizeof(mmap_event->event) + size;
+
+	cpuctx = &get_cpu_var(perf_cpu_context);
+	perf_counter_mmap_ctx(&cpuctx->ctx, mmap_event);
+	put_cpu_var(perf_cpu_context);
+
+	perf_counter_mmap_ctx(&current->perf_counter_ctx, mmap_event);
+
+	kfree(buf);
+}
+
+void perf_counter_mmap(unsigned long addr, unsigned long len,
+		       unsigned long pgoff, struct file *file)
+{
+	struct perf_mmap_event mmap_event = {
+		.file   = file,
+		.event  = {
+			.header = { .type = PERF_EVENT_MMAP, },
+			.pid	= current->group_leader->pid,
+			.tid	= current->pid,
+			.start  = addr,
+			.len    = len,
+			.pgoff  = pgoff,
+		},
+	};
+
+	perf_counter_mmap_event(&mmap_event);
+}
+
+void perf_counter_munmap(unsigned long addr, unsigned long len,
+			 unsigned long pgoff, struct file *file)
+{
+	struct perf_mmap_event mmap_event = {
+		.file   = file,
+		.event  = {
+			.header = { .type = PERF_EVENT_MUNMAP, },
+			.pid	= current->group_leader->pid,
+			.tid	= current->pid,
+			.start  = addr,
+			.len    = len,
+			.pgoff  = pgoff,
+		},
+	};
+
+	perf_counter_mmap_event(&mmap_event);
+}
+
+/*
  * Generic software counter infrastructure
  */
 
Index: linux-2.6/mm/mmap.c
===================================================================
--- linux-2.6.orig/mm/mmap.c
+++ linux-2.6/mm/mmap.c
@@ -27,6 +27,7 @@
 #include <linux/mempolicy.h>
 #include <linux/rmap.h>
 #include <linux/mmu_notifier.h>
+#include <linux/perf_counter.h>
 
 #include <asm/uaccess.h>
 #include <asm/cacheflush.h>
@@ -1219,6 +1220,9 @@ munmap_back:
 	if (correct_wcount)
 		atomic_inc(&inode->i_writecount);
 out:
+	if (vm_flags & VM_EXEC)
+		perf_counter_mmap(addr, len, pgoff, file);
+
 	mm->total_vm += len >> PAGE_SHIFT;
 	vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
 	if (vm_flags & VM_LOCKED) {
@@ -1752,6 +1756,12 @@ static void remove_vma_list(struct mm_st
 	do {
 		long nrpages = vma_pages(vma);
 
+		if (vma->vm_flags & VM_EXEC) {
+			perf_counter_munmap(vma->vm_start,
+					nrpages << PAGE_SIZE,
+					vma->vm_pgoff, vma->vm_file);
+		}
+
 		mm->total_vm -= nrpages;
 		vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages);
 		vma = remove_vma(vma);

-- 

Re: [RFC][PATCH 2/3] perf_counter: executable mmap() information

[Paul Mackerras]

Peter Zijlstra writes:

> --- linux-2.6.orig/include/linux/perf_counter.h
> +++ linux-2.6/include/linux/perf_counter.h
> @@ -137,7 +137,9 @@ struct perf_counter_hw_event {
>  				exclude_kernel :  1, /* ditto kernel          */
>  				exclude_hv     :  1, /* ditto hypervisor      */
>  				exclude_idle   :  1, /* don't count when idle */
> -				include_tid    :  1, /* include the tid */
> +				include_tid    :  1, /* include the tid       */
> +				mmap           :  1, /* include mmap data     */
> +				munmap         :  1, /* include munmap data   */
>  
>  				__reserved_1   : 54;

Nit: need to adjust the size of __reserved_1 here.  Or maybe just get
rid of it?

Paul.

Re: [RFC][PATCH 2/3] perf_counter: executable mmap() information

[Ingo Molnar]

* Paul Mackerras <paulus@samba.org> wrote:

> Peter Zijlstra writes:
> 
> > --- linux-2.6.orig/include/linux/perf_counter.h
> > +++ linux-2.6/include/linux/perf_counter.h
> > @@ -137,7 +137,9 @@ struct perf_counter_hw_event {
> >  				exclude_kernel :  1, /* ditto kernel          */
> >  				exclude_hv     :  1, /* ditto hypervisor      */
> >  				exclude_idle   :  1, /* don't count when idle */
> > -				include_tid    :  1, /* include the tid */
> > +				include_tid    :  1, /* include the tid       */
> > +				mmap           :  1, /* include mmap data     */
> > +				munmap         :  1, /* include munmap data   */
> >  
> >  				__reserved_1   : 54;
> 
> Nit: need to adjust the size of __reserved_1 here.  Or maybe just 
> get rid of it?

it's nice to have a constant reminder about how many bits there are 
left.

	Ingo

Re: [RFC][PATCH 2/3] perf_counter: executable mmap() information

[Paul Mackerras]

Ingo Molnar writes:

> * Paul Mackerras <paulus@samba.org> wrote:
> 
> > Peter Zijlstra writes:
> > 
> > > --- linux-2.6.orig/include/linux/perf_counter.h
> > > +++ linux-2.6/include/linux/perf_counter.h
> > > @@ -137,7 +137,9 @@ struct perf_counter_hw_event {
> > >  				exclude_kernel :  1, /* ditto kernel          */
> > >  				exclude_hv     :  1, /* ditto hypervisor      */
> > >  				exclude_idle   :  1, /* don't count when idle */
> > > -				include_tid    :  1, /* include the tid */
> > > +				include_tid    :  1, /* include the tid       */
> > > +				mmap           :  1, /* include mmap data     */
> > > +				munmap         :  1, /* include munmap data   */
> > >  
> > >  				__reserved_1   : 54;
> > 
> > Nit: need to adjust the size of __reserved_1 here.  Or maybe just 
> > get rid of it?
> 
> it's nice to have a constant reminder about how many bits there are 
> left.

Fair enough, but as it stands, we've changed the ABI, so we need to
fix it.

Paul.

Re: [RFC][PATCH 2/3] perf_counter: executable mmap() information

[Paul Mackerras]

I wrote:

> Fair enough, but as it stands, we've changed the ABI, so we need to
> fix it.

I meant of course that that patch would change the ABI if it were
accepted...

Paul.

[RFC][PATCH 3/3] perf_counter: kerneltop: parse the mmap data stream

[Peter Zijlstra]

[-- Attachment #1: kerneltop-mmap-events.patch --]
[-- Type: text/plain, Size: 2394 bytes --]

frob the kerneltop code to print the mmap data in the stream

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 Documentation/perf_counter/kerneltop.c |   39 ++++++++++++++++++++++++++++-----
 1 file changed, 34 insertions(+), 5 deletions(-)

Index: linux-2.6/Documentation/perf_counter/kerneltop.c
===================================================================
--- linux-2.6.orig/Documentation/perf_counter/kerneltop.c
+++ linux-2.6/Documentation/perf_counter/kerneltop.c
@@ -1184,12 +1184,29 @@ static void mmap_read(struct mmap_data *
 	last_read = this_read;
 
 	for (; old != head;) {
-		struct event_struct {
+		struct ip_event {
 			struct perf_event_header header;
 			__u64 ip;
 			__u32 pid, tid;
-		} *event = (struct event_struct *)&data[old & md->mask];
-		struct event_struct event_copy;
+		};
+		struct mmap_event {
+			struct perf_event_header header;
+			__u32 pid, tid;
+			__u64 start;
+			__u64 len;
+			__u64 pgoff;
+			char filename[PATH_MAX];
+		};
+
+		typedef union event_union {
+			struct perf_event_header header;
+			struct ip_event ip;
+			struct mmap_event mmap;
+		} event_t;
+
+		event_t *event = (event_t *)&data[old & md->mask];
+
+		event_t event_copy;
 
 		unsigned int size = event->header.size;
 
@@ -1199,7 +1216,7 @@ static void mmap_read(struct mmap_data *
 		 */
 		if ((old & md->mask) + size != ((old + size) & md->mask)) {
 			unsigned int offset = old;
-			unsigned int len = sizeof(*event), cpy;
+			unsigned int len = min(sizeof(*event), size), cpy;
 			void *dst = &event_copy;
 
 			do {
@@ -1218,7 +1235,18 @@ static void mmap_read(struct mmap_data *
 		switch (event->header.type) {
 		case PERF_EVENT_IP:
 		case PERF_EVENT_IP | __PERF_EVENT_TID:
-			process_event(event->ip, md->counter);
+			process_event(event->ip.ip, md->counter);
+			break;
+
+		case PERF_EVENT_MMAP:
+		case PERF_EVENT_MUNMAP:
+			printf("%s: %Lu %Lu %Lu %s\n",
+					event->header.type == PERF_EVENT_MMAP
+					  ? "mmap" : "munmap",
+					event->mmap.start,
+					event->mmap.len,
+					event->mmap.pgoff,
+					event->mmap.filename);
 			break;
 		}
 	}
@@ -1267,6 +1295,7 @@ int main(int argc, char *argv[])
 			hw_event.record_type	= PERF_RECORD_IRQ;
 			hw_event.nmi		= nmi;
 			hw_event.include_tid	= 1;
+			hw_event.mmap		= 1;
 
 			fd[i][counter] = sys_perf_counter_open(&hw_event, tid, cpu, group_fd, 0);
 			if (fd[i][counter] < 0) {

--