[PATCH v0 0/6] perf/x86/intel/pt: Misc updates

[PATCH v0 0/6] perf/x86/intel/pt: Misc updates

[Alexander Shishkin]

Hi Peter,

Here are updates that I have for the PT driver. The biggest change is
6/6, it gets rid of the reverse lookup table that the driver uses to
find ToPA (SG) entries by the page offset. With the high order page
allocations in the AUX buffer, the cost of runtime lookup should be
minimal, and we get to free up some memory that the table occupies.
Plus, we get to allocate 2G (and up) PT buffers should we be so
inclined.

Others are small reworks and cleanups striving to make the code easier
on the eyes.

Alexander Shishkin (6):
  perf/x86/intel/pt: Clean up ToPA allocation path
  perf/x86/intel/pt: Use helpers to obtain ToPA entry size
  perf/x86/intel/pt: Use pointer arithmetics instead in ToPA entry
    calculation
  perf/x86/intel/pt: Split ToPA metadata and page layout
  perf/x86/intel/pt: Free up space in a ToPA descriptor
  perf/x86/intel/pt: Get rid of reverse lookup table for ToPA

 arch/x86/events/intel/pt.c | 325 +++++++++++++++++++++++--------------
 arch/x86/events/intel/pt.h |  12 +-
 2 files changed, 210 insertions(+), 127 deletions(-)

-- 
2.23.0.rc1

[PATCH v0 1/6] perf/x86/intel/pt: Clean up ToPA allocation path

[Alexander Shishkin]

Some of the allocation parameters are passed as function arguments,
while the CPU number for per-cpu allocation is passed via the buffer
object. There's no reason for this.

Pass the CPU as a function argument instead.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
 arch/x86/events/intel/pt.c | 15 +++++++--------
 arch/x86/events/intel/pt.h |  2 --
 2 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index a7318c29242e..b029f32edae2 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -670,7 +670,7 @@ static bool topa_table_full(struct topa *topa)
  *
  * Return:	0 on success or error code.
  */
-static int topa_insert_pages(struct pt_buffer *buf, gfp_t gfp)
+static int topa_insert_pages(struct pt_buffer *buf, int cpu, gfp_t gfp)
 {
 	struct topa *topa = buf->last;
 	int order = 0;
@@ -681,7 +681,7 @@ static int topa_insert_pages(struct pt_buffer *buf, gfp_t gfp)
 		order = page_private(p);
 
 	if (topa_table_full(topa)) {
-		topa = topa_alloc(buf->cpu, gfp);
+		topa = topa_alloc(cpu, gfp);
 		if (!topa)
 			return -ENOMEM;
 
@@ -1061,20 +1061,20 @@ static void pt_buffer_fini_topa(struct pt_buffer *buf)
  * @size:	Total size of all regions within this ToPA.
  * @gfp:	Allocation flags.
  */
-static int pt_buffer_init_topa(struct pt_buffer *buf, unsigned long nr_pages,
-			       gfp_t gfp)
+static int pt_buffer_init_topa(struct pt_buffer *buf, int cpu,
+			       unsigned long nr_pages, gfp_t gfp)
 {
 	struct topa *topa;
 	int err;
 
-	topa = topa_alloc(buf->cpu, gfp);
+	topa = topa_alloc(cpu, gfp);
 	if (!topa)
 		return -ENOMEM;
 
 	topa_insert_table(buf, topa);
 
 	while (buf->nr_pages < nr_pages) {
-		err = topa_insert_pages(buf, gfp);
+		err = topa_insert_pages(buf, cpu, gfp);
 		if (err) {
 			pt_buffer_fini_topa(buf);
 			return -ENOMEM;
@@ -1124,13 +1124,12 @@ pt_buffer_setup_aux(struct perf_event *event, void **pages,
 	if (!buf)
 		return NULL;
 
-	buf->cpu = cpu;
 	buf->snapshot = snapshot;
 	buf->data_pages = pages;
 
 	INIT_LIST_HEAD(&buf->tables);
 
-	ret = pt_buffer_init_topa(buf, nr_pages, GFP_KERNEL);
+	ret = pt_buffer_init_topa(buf, cpu, nr_pages, GFP_KERNEL);
 	if (ret) {
 		kfree(buf);
 		return NULL;
diff --git a/arch/x86/events/intel/pt.h b/arch/x86/events/intel/pt.h
index 63fe4063fbd6..8de8ed089697 100644
--- a/arch/x86/events/intel/pt.h
+++ b/arch/x86/events/intel/pt.h
@@ -53,7 +53,6 @@ struct pt_pmu {
 /**
  * struct pt_buffer - buffer configuration; one buffer per task_struct or
  *		cpu, depending on perf event configuration
- * @cpu:	cpu for per-cpu allocation
  * @tables:	list of ToPA tables in this buffer
  * @first:	shorthand for first topa table
  * @last:	shorthand for last topa table
@@ -71,7 +70,6 @@ struct pt_pmu {
  * @topa_index:	table of topa entries indexed by page offset
  */
 struct pt_buffer {
-	int			cpu;
 	struct list_head	tables;
 	struct topa		*first, *last, *cur;
 	unsigned int		cur_idx;
-- 
2.23.0.rc1

[tip: perf/core] perf/x86/intel/pt: Clean up ToPA allocation path

[tip-bot2 for Alexander Shishkin]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     90583af61d0c0d2826f42a297a03645b35c49085
Gitweb:        https://git.kernel.org/tip/90583af61d0c0d2826f42a297a03645b35c49085
Author:        Alexander Shishkin <alexander.shishkin@linux.intel.com>
AuthorDate:    Wed, 21 Aug 2019 15:47:22 +03:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 26 Aug 2019 12:00:12 +02:00

perf/x86/intel/pt: Clean up ToPA allocation path

Some of the allocation parameters are passed as function arguments,
while the CPU number for per-cpu allocation is passed via the buffer
object. There's no reason for this.

Pass the CPU as a function argument instead.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/20190821124727.73310-2-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/events/intel/pt.c | 15 +++++++--------
 arch/x86/events/intel/pt.h |  2 --
 2 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index d3dc227..9d9258f 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -670,7 +670,7 @@ static bool topa_table_full(struct topa *topa)
  *
  * Return:	0 on success or error code.
  */
-static int topa_insert_pages(struct pt_buffer *buf, gfp_t gfp)
+static int topa_insert_pages(struct pt_buffer *buf, int cpu, gfp_t gfp)
 {
 	struct topa *topa = buf->last;
 	int order = 0;
@@ -681,7 +681,7 @@ static int topa_insert_pages(struct pt_buffer *buf, gfp_t gfp)
 		order = page_private(p);
 
 	if (topa_table_full(topa)) {
-		topa = topa_alloc(buf->cpu, gfp);
+		topa = topa_alloc(cpu, gfp);
 		if (!topa)
 			return -ENOMEM;
 
@@ -1061,20 +1061,20 @@ static void pt_buffer_fini_topa(struct pt_buffer *buf)
  * @size:	Total size of all regions within this ToPA.
  * @gfp:	Allocation flags.
  */
-static int pt_buffer_init_topa(struct pt_buffer *buf, unsigned long nr_pages,
-			       gfp_t gfp)
+static int pt_buffer_init_topa(struct pt_buffer *buf, int cpu,
+			       unsigned long nr_pages, gfp_t gfp)
 {
 	struct topa *topa;
 	int err;
 
-	topa = topa_alloc(buf->cpu, gfp);
+	topa = topa_alloc(cpu, gfp);
 	if (!topa)
 		return -ENOMEM;
 
 	topa_insert_table(buf, topa);
 
 	while (buf->nr_pages < nr_pages) {
-		err = topa_insert_pages(buf, gfp);
+		err = topa_insert_pages(buf, cpu, gfp);
 		if (err) {
 			pt_buffer_fini_topa(buf);
 			return -ENOMEM;
@@ -1124,13 +1124,12 @@ pt_buffer_setup_aux(struct perf_event *event, void **pages,
 	if (!buf)
 		return NULL;
 
-	buf->cpu = cpu;
 	buf->snapshot = snapshot;
 	buf->data_pages = pages;
 
 	INIT_LIST_HEAD(&buf->tables);
 
-	ret = pt_buffer_init_topa(buf, nr_pages, GFP_KERNEL);
+	ret = pt_buffer_init_topa(buf, cpu, nr_pages, GFP_KERNEL);
 	if (ret) {
 		kfree(buf);
 		return NULL;
diff --git a/arch/x86/events/intel/pt.h b/arch/x86/events/intel/pt.h
index 63fe406..8de8ed0 100644
--- a/arch/x86/events/intel/pt.h
+++ b/arch/x86/events/intel/pt.h
@@ -53,7 +53,6 @@ struct pt_pmu {
 /**
  * struct pt_buffer - buffer configuration; one buffer per task_struct or
  *		cpu, depending on perf event configuration
- * @cpu:	cpu for per-cpu allocation
  * @tables:	list of ToPA tables in this buffer
  * @first:	shorthand for first topa table
  * @last:	shorthand for last topa table
@@ -71,7 +70,6 @@ struct pt_pmu {
  * @topa_index:	table of topa entries indexed by page offset
  */
 struct pt_buffer {
-	int			cpu;
 	struct list_head	tables;
 	struct topa		*first, *last, *cur;
 	unsigned int		cur_idx;

[PATCH v0 2/6] perf/x86/intel/pt: Use helpers to obtain ToPA entry size

[Alexander Shishkin]

There are a few places in the PT driver that need to obtain the size of
a ToPA entry, some of them for the current ToPA entry in the buffer.
Use helpers for those, to make the lines shorter and more readable.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
 arch/x86/events/intel/pt.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index b029f32edae2..831163a1b41a 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -572,6 +572,7 @@ struct topa {
 
 /* make -1 stand for the last table entry */
 #define TOPA_ENTRY(t, i) ((i) == -1 ? &(t)->table[(t)->last] : &(t)->table[(i)])
+#define TOPA_ENTRY_SIZE(t, i) (sizes(TOPA_ENTRY((t), (i))->size))
 
 /**
  * topa_alloc() - allocate page-sized ToPA table
@@ -771,7 +772,7 @@ static void pt_update_head(struct pt *pt)
 
 	/* offset of the current output region within this table */
 	for (topa_idx = 0; topa_idx < buf->cur_idx; topa_idx++)
-		base += sizes(buf->cur->table[topa_idx].size);
+		base += TOPA_ENTRY_SIZE(buf->cur, topa_idx);
 
 	if (buf->snapshot) {
 		local_set(&buf->data_size, base);
@@ -800,7 +801,7 @@ static void *pt_buffer_region(struct pt_buffer *buf)
  */
 static size_t pt_buffer_region_size(struct pt_buffer *buf)
 {
-	return sizes(buf->cur->table[buf->cur_idx].size);
+	return TOPA_ENTRY_SIZE(buf->cur, buf->cur_idx);
 }
 
 /**
@@ -830,7 +831,7 @@ static void pt_handle_status(struct pt *pt)
 		 * know.
 		 */
 		if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries) ||
-		    buf->output_off == sizes(TOPA_ENTRY(buf->cur, buf->cur_idx)->size)) {
+		    buf->output_off == pt_buffer_region_size(buf)) {
 			perf_aux_output_flag(&pt->handle,
 			                     PERF_AUX_FLAG_TRUNCATED);
 			advance++;
@@ -925,8 +926,7 @@ static int pt_buffer_reset_markers(struct pt_buffer *buf,
 	unsigned long idx, npages, wakeup;
 
 	/* can't stop in the middle of an output region */
-	if (buf->output_off + handle->size + 1 <
-	    sizes(TOPA_ENTRY(buf->cur, buf->cur_idx)->size)) {
+	if (buf->output_off + handle->size + 1 < pt_buffer_region_size(buf)) {
 		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
 		return -EINVAL;
 	}
@@ -1032,7 +1032,7 @@ static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head)
 	buf->cur = (struct topa *)((unsigned long)buf->topa_index[pg] & PAGE_MASK);
 	buf->cur_idx = ((unsigned long)buf->topa_index[pg] -
 			(unsigned long)buf->cur) / sizeof(struct topa_entry);
-	buf->output_off = head & (sizes(buf->cur->table[buf->cur_idx].size) - 1);
+	buf->output_off = head & (pt_buffer_region_size(buf) - 1);
 
 	local64_set(&buf->head, head);
 	local_set(&buf->data_size, 0);
-- 
2.23.0.rc1

[tip: perf/core] perf/x86/intel/pt: Use helpers to obtain ToPA entry size

[tip-bot2 for Alexander Shishkin]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     fffec50f541ace292383c0cbe9a2a97d16d201c6
Gitweb:        https://git.kernel.org/tip/fffec50f541ace292383c0cbe9a2a97d16d201c6
Author:        Alexander Shishkin <alexander.shishkin@linux.intel.com>
AuthorDate:    Wed, 21 Aug 2019 15:47:23 +03:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 26 Aug 2019 12:00:13 +02:00

perf/x86/intel/pt: Use helpers to obtain ToPA entry size

There are a few places in the PT driver that need to obtain the size of
a ToPA entry, some of them for the current ToPA entry in the buffer.
Use helpers for those, to make the lines shorter and more readable.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/20190821124727.73310-3-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/events/intel/pt.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index 9d9258f..f269875 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -572,6 +572,7 @@ struct topa {
 
 /* make -1 stand for the last table entry */
 #define TOPA_ENTRY(t, i) ((i) == -1 ? &(t)->table[(t)->last] : &(t)->table[(i)])
+#define TOPA_ENTRY_SIZE(t, i) (sizes(TOPA_ENTRY((t), (i))->size))
 
 /**
  * topa_alloc() - allocate page-sized ToPA table
@@ -771,7 +772,7 @@ static void pt_update_head(struct pt *pt)
 
 	/* offset of the current output region within this table */
 	for (topa_idx = 0; topa_idx < buf->cur_idx; topa_idx++)
-		base += sizes(buf->cur->table[topa_idx].size);
+		base += TOPA_ENTRY_SIZE(buf->cur, topa_idx);
 
 	if (buf->snapshot) {
 		local_set(&buf->data_size, base);
@@ -800,7 +801,7 @@ static void *pt_buffer_region(struct pt_buffer *buf)
  */
 static size_t pt_buffer_region_size(struct pt_buffer *buf)
 {
-	return sizes(buf->cur->table[buf->cur_idx].size);
+	return TOPA_ENTRY_SIZE(buf->cur, buf->cur_idx);
 }
 
 /**
@@ -830,7 +831,7 @@ static void pt_handle_status(struct pt *pt)
 		 * know.
 		 */
 		if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries) ||
-		    buf->output_off == sizes(TOPA_ENTRY(buf->cur, buf->cur_idx)->size)) {
+		    buf->output_off == pt_buffer_region_size(buf)) {
 			perf_aux_output_flag(&pt->handle,
 			                     PERF_AUX_FLAG_TRUNCATED);
 			advance++;
@@ -925,8 +926,7 @@ static int pt_buffer_reset_markers(struct pt_buffer *buf,
 	unsigned long idx, npages, wakeup;
 
 	/* can't stop in the middle of an output region */
-	if (buf->output_off + handle->size + 1 <
-	    sizes(TOPA_ENTRY(buf->cur, buf->cur_idx)->size)) {
+	if (buf->output_off + handle->size + 1 < pt_buffer_region_size(buf)) {
 		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
 		return -EINVAL;
 	}
@@ -1032,7 +1032,7 @@ static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head)
 	buf->cur = (struct topa *)((unsigned long)buf->topa_index[pg] & PAGE_MASK);
 	buf->cur_idx = ((unsigned long)buf->topa_index[pg] -
 			(unsigned long)buf->cur) / sizeof(struct topa_entry);
-	buf->output_off = head & (sizes(buf->cur->table[buf->cur_idx].size) - 1);
+	buf->output_off = head & (pt_buffer_region_size(buf) - 1);
 
 	local64_set(&buf->head, head);
 	local_set(&buf->data_size, 0);

[PATCH v0 3/6] perf/x86/intel/pt: Use pointer arithmetics instead in ToPA entry calculation

[Alexander Shishkin]

Currently, pt_buffer_reset_offsets() calculates the current ToPA entry by
casting pointers to addresses and performing ungainly subtractions and
divisions instead of a simpler pointer arithmetic, which would be perfectly
applicable in that case. Fix that.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
 arch/x86/events/intel/pt.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index 831163a1b41a..15e7c11e3460 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -1030,8 +1030,7 @@ static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head)
 	pg = pt_topa_next_entry(buf, pg);
 
 	buf->cur = (struct topa *)((unsigned long)buf->topa_index[pg] & PAGE_MASK);
-	buf->cur_idx = ((unsigned long)buf->topa_index[pg] -
-			(unsigned long)buf->cur) / sizeof(struct topa_entry);
+	buf->cur_idx = buf->topa_index[pg] - TOPA_ENTRY(buf->cur, 0);
 	buf->output_off = head & (pt_buffer_region_size(buf) - 1);
 
 	local64_set(&buf->head, head);
-- 
2.23.0.rc1

[tip: perf/core] perf/x86/intel/pt: Use pointer arithmetics instead in ToPA entry calculation

[tip-bot2 for Alexander Shishkin]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     539f7c26b41d4ed7d88dd9756de3966ae7ca07b4
Gitweb:        https://git.kernel.org/tip/539f7c26b41d4ed7d88dd9756de3966ae7ca07b4
Author:        Alexander Shishkin <alexander.shishkin@linux.intel.com>
AuthorDate:    Wed, 21 Aug 2019 15:47:24 +03:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 26 Aug 2019 12:00:13 +02:00

perf/x86/intel/pt: Use pointer arithmetics instead in ToPA entry calculation

Currently, pt_buffer_reset_offsets() calculates the current ToPA entry by
casting pointers to addresses and performing ungainly subtractions and
divisions instead of a simpler pointer arithmetic, which would be perfectly
applicable in that case. Fix that.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/20190821124727.73310-4-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/events/intel/pt.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index f269875..188d45f 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -1030,8 +1030,7 @@ static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head)
 	pg = pt_topa_next_entry(buf, pg);
 
 	buf->cur = (struct topa *)((unsigned long)buf->topa_index[pg] & PAGE_MASK);
-	buf->cur_idx = ((unsigned long)buf->topa_index[pg] -
-			(unsigned long)buf->cur) / sizeof(struct topa_entry);
+	buf->cur_idx = buf->topa_index[pg] - TOPA_ENTRY(buf->cur, 0);
 	buf->output_off = head & (pt_buffer_region_size(buf) - 1);
 
 	local64_set(&buf->head, head);

[PATCH v0 4/6] perf/x86/intel/pt: Split ToPA metadata and page layout

[Alexander Shishkin]

PT uses page sized ToPA tables, where the ToPA table resides at the bottom
and its driver-specific metadata taking up a few words at the top of the
page. The split is currently calculated manually and needs to be redone
every time a field is added to or removed from the metadata structure.
Also, the 32-bit version can be made smaller.

By splitting the table and metadata into separate structures, we are making
the compiler figure out the division of the page.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
 arch/x86/events/intel/pt.c | 93 ++++++++++++++++++++++++--------------
 1 file changed, 60 insertions(+), 33 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index 15e7c11e3460..e7b0f8f4f1b0 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -545,16 +545,8 @@ static void pt_config_buffer(void *buf, unsigned int topa_idx,
 	wrmsrl(MSR_IA32_RTIT_OUTPUT_MASK, reg);
 }
 
-/*
- * Keep ToPA table-related metadata on the same page as the actual table,
- * taking up a few words from the top
- */
-
-#define TENTS_PER_PAGE (((PAGE_SIZE - 40) / sizeof(struct topa_entry)) - 1)
-
 /**
- * struct topa - page-sized ToPA table with metadata at the top
- * @table:	actual ToPA table entries, as understood by PT hardware
+ * struct topa - ToPA metadata
  * @list:	linkage to struct pt_buffer's list of tables
  * @phys:	physical address of this page
  * @offset:	offset of the first entry in this table in the buffer
@@ -562,7 +554,6 @@ static void pt_config_buffer(void *buf, unsigned int topa_idx,
  * @last:	index of the last initialized entry in this table
  */
 struct topa {
-	struct topa_entry	table[TENTS_PER_PAGE];
 	struct list_head	list;
 	u64			phys;
 	u64			offset;
@@ -570,8 +561,39 @@ struct topa {
 	int			last;
 };
 
+/*
+ * Keep ToPA table-related metadata on the same page as the actual table,
+ * taking up a few words from the top
+ */
+
+#define TENTS_PER_PAGE	\
+	((PAGE_SIZE - sizeof(struct topa)) / sizeof(struct topa_entry))
+
+/**
+ * struct topa_page - page-sized ToPA table with metadata at the top
+ * @table:	actual ToPA table entries, as understood by PT hardware
+ * @topa:	metadata
+ */
+struct topa_page {
+	struct topa_entry	table[TENTS_PER_PAGE];
+	struct topa		topa;
+};
+
+static inline struct topa_page *topa_to_page(struct topa *topa)
+{
+	return container_of(topa, struct topa_page, topa);
+}
+
+static inline struct topa_page *topa_entry_to_page(struct topa_entry *te)
+{
+	return (struct topa_page *)((unsigned long)te & PAGE_MASK);
+}
+
 /* make -1 stand for the last table entry */
-#define TOPA_ENTRY(t, i) ((i) == -1 ? &(t)->table[(t)->last] : &(t)->table[(i)])
+#define TOPA_ENTRY(t, i)				\
+	((i) == -1					\
+		? &topa_to_page(t)->table[(t)->last]	\
+		: &topa_to_page(t)->table[(i)])
 #define TOPA_ENTRY_SIZE(t, i) (sizes(TOPA_ENTRY((t), (i))->size))
 
 /**
@@ -584,27 +606,27 @@ struct topa {
 static struct topa *topa_alloc(int cpu, gfp_t gfp)
 {
 	int node = cpu_to_node(cpu);
-	struct topa *topa;
+	struct topa_page *tp;
 	struct page *p;
 
 	p = alloc_pages_node(node, gfp | __GFP_ZERO, 0);
 	if (!p)
 		return NULL;
 
-	topa = page_address(p);
-	topa->last = 0;
-	topa->phys = page_to_phys(p);
+	tp = page_address(p);
+	tp->topa.last = 0;
+	tp->topa.phys = page_to_phys(p);
 
 	/*
 	 * In case of singe-entry ToPA, always put the self-referencing END
 	 * link as the 2nd entry in the table
 	 */
 	if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries)) {
-		TOPA_ENTRY(topa, 1)->base = topa->phys >> TOPA_SHIFT;
-		TOPA_ENTRY(topa, 1)->end = 1;
+		TOPA_ENTRY(&tp->topa, 1)->base = tp->topa.phys;
+		TOPA_ENTRY(&tp->topa, 1)->end = 1;
 	}
 
-	return topa;
+	return &tp->topa;
 }
 
 /**
@@ -714,22 +736,23 @@ static void pt_topa_dump(struct pt_buffer *buf)
 	struct topa *topa;
 
 	list_for_each_entry(topa, &buf->tables, list) {
+		struct topa_page *tp = topa_to_page(topa);
 		int i;
 
-		pr_debug("# table @%p (%016Lx), off %llx size %zx\n", topa->table,
+		pr_debug("# table @%p (%016Lx), off %llx size %zx\n", tp->table,
 			 topa->phys, topa->offset, topa->size);
 		for (i = 0; i < TENTS_PER_PAGE; i++) {
 			pr_debug("# entry @%p (%lx sz %u %c%c%c) raw=%16llx\n",
-				 &topa->table[i],
-				 (unsigned long)topa->table[i].base << TOPA_SHIFT,
-				 sizes(topa->table[i].size),
-				 topa->table[i].end ?  'E' : ' ',
-				 topa->table[i].intr ? 'I' : ' ',
-				 topa->table[i].stop ? 'S' : ' ',
-				 *(u64 *)&topa->table[i]);
+				 &tp->table[i],
+				 (unsigned long)tp->table[i].base << TOPA_SHIFT,
+				 sizes(tp->table[i].size),
+				 tp->table[i].end ?  'E' : ' ',
+				 tp->table[i].intr ? 'I' : ' ',
+				 tp->table[i].stop ? 'S' : ' ',
+				 *(u64 *)&tp->table[i]);
 			if ((intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries) &&
-			     topa->table[i].stop) ||
-			    topa->table[i].end)
+			     tp->table[i].stop) ||
+			    tp->table[i].end)
 				break;
 		}
 	}
@@ -792,7 +815,7 @@ static void pt_update_head(struct pt *pt)
  */
 static void *pt_buffer_region(struct pt_buffer *buf)
 {
-	return phys_to_virt(buf->cur->table[buf->cur_idx].base << TOPA_SHIFT);
+	return phys_to_virt(TOPA_ENTRY(buf->cur, buf->cur_idx)->base << TOPA_SHIFT);
 }
 
 /**
@@ -869,9 +892,11 @@ static void pt_handle_status(struct pt *pt)
 static void pt_read_offset(struct pt_buffer *buf)
 {
 	u64 offset, base_topa;
+	struct topa_page *tp;
 
 	rdmsrl(MSR_IA32_RTIT_OUTPUT_BASE, base_topa);
-	buf->cur = phys_to_virt(base_topa);
+	tp = phys_to_virt(base_topa);
+	buf->cur = &tp->topa;
 
 	rdmsrl(MSR_IA32_RTIT_OUTPUT_MASK, offset);
 	/* offset within current output region */
@@ -1021,6 +1046,7 @@ static void pt_buffer_setup_topa_index(struct pt_buffer *buf)
  */
 static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head)
 {
+	struct topa_page *cur_tp;
 	int pg;
 
 	if (buf->snapshot)
@@ -1029,7 +1055,8 @@ static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head)
 	pg = (head >> PAGE_SHIFT) & (buf->nr_pages - 1);
 	pg = pt_topa_next_entry(buf, pg);
 
-	buf->cur = (struct topa *)((unsigned long)buf->topa_index[pg] & PAGE_MASK);
+	cur_tp = topa_entry_to_page(buf->topa_index[pg]);
+	buf->cur = &cur_tp->topa;
 	buf->cur_idx = buf->topa_index[pg] - TOPA_ENTRY(buf->cur, 0);
 	buf->output_off = head & (pt_buffer_region_size(buf) - 1);
 
@@ -1294,7 +1321,7 @@ void intel_pt_interrupt(void)
 			return;
 		}
 
-		pt_config_buffer(buf->cur->table, buf->cur_idx,
+		pt_config_buffer(topa_to_page(buf->cur)->table, buf->cur_idx,
 				 buf->output_off);
 		pt_config(event);
 	}
@@ -1359,7 +1386,7 @@ static void pt_event_start(struct perf_event *event, int mode)
 	WRITE_ONCE(pt->handle_nmi, 1);
 	hwc->state = 0;
 
-	pt_config_buffer(buf->cur->table, buf->cur_idx,
+	pt_config_buffer(topa_to_page(buf->cur)->table, buf->cur_idx,
 			 buf->output_off);
 	pt_config(event);
 
-- 
2.23.0.rc1

[tip: perf/core] perf/x86/intel/pt: Split ToPA metadata and page layout

[tip-bot2 for Alexander Shishkin]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     38bb8d77d0b932a0773b5de2ef42479409314f96
Gitweb:        https://git.kernel.org/tip/38bb8d77d0b932a0773b5de2ef42479409314f96
Author:        Alexander Shishkin <alexander.shishkin@linux.intel.com>
AuthorDate:    Wed, 21 Aug 2019 15:47:25 +03:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 26 Aug 2019 12:00:14 +02:00

perf/x86/intel/pt: Split ToPA metadata and page layout

PT uses page sized ToPA tables, where the ToPA table resides at the bottom
and its driver-specific metadata taking up a few words at the top of the
page. The split is currently calculated manually and needs to be redone
every time a field is added to or removed from the metadata structure.
Also, the 32-bit version can be made smaller.

By splitting the table and metadata into separate structures, we are making
the compiler figure out the division of the page.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/20190821124727.73310-5-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/events/intel/pt.c | 93 +++++++++++++++++++++++--------------
 1 file changed, 60 insertions(+), 33 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index 188d45f..2e3f068 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -545,16 +545,8 @@ static void pt_config_buffer(void *buf, unsigned int topa_idx,
 	wrmsrl(MSR_IA32_RTIT_OUTPUT_MASK, reg);
 }
 
-/*
- * Keep ToPA table-related metadata on the same page as the actual table,
- * taking up a few words from the top
- */
-
-#define TENTS_PER_PAGE (((PAGE_SIZE - 40) / sizeof(struct topa_entry)) - 1)
-
 /**
- * struct topa - page-sized ToPA table with metadata at the top
- * @table:	actual ToPA table entries, as understood by PT hardware
+ * struct topa - ToPA metadata
  * @list:	linkage to struct pt_buffer's list of tables
  * @phys:	physical address of this page
  * @offset:	offset of the first entry in this table in the buffer
@@ -562,7 +554,6 @@ static void pt_config_buffer(void *buf, unsigned int topa_idx,
  * @last:	index of the last initialized entry in this table
  */
 struct topa {
-	struct topa_entry	table[TENTS_PER_PAGE];
 	struct list_head	list;
 	u64			phys;
 	u64			offset;
@@ -570,8 +561,39 @@ struct topa {
 	int			last;
 };
 
+/*
+ * Keep ToPA table-related metadata on the same page as the actual table,
+ * taking up a few words from the top
+ */
+
+#define TENTS_PER_PAGE	\
+	((PAGE_SIZE - sizeof(struct topa)) / sizeof(struct topa_entry))
+
+/**
+ * struct topa_page - page-sized ToPA table with metadata at the top
+ * @table:	actual ToPA table entries, as understood by PT hardware
+ * @topa:	metadata
+ */
+struct topa_page {
+	struct topa_entry	table[TENTS_PER_PAGE];
+	struct topa		topa;
+};
+
+static inline struct topa_page *topa_to_page(struct topa *topa)
+{
+	return container_of(topa, struct topa_page, topa);
+}
+
+static inline struct topa_page *topa_entry_to_page(struct topa_entry *te)
+{
+	return (struct topa_page *)((unsigned long)te & PAGE_MASK);
+}
+
 /* make -1 stand for the last table entry */
-#define TOPA_ENTRY(t, i) ((i) == -1 ? &(t)->table[(t)->last] : &(t)->table[(i)])
+#define TOPA_ENTRY(t, i)				\
+	((i) == -1					\
+		? &topa_to_page(t)->table[(t)->last]	\
+		: &topa_to_page(t)->table[(i)])
 #define TOPA_ENTRY_SIZE(t, i) (sizes(TOPA_ENTRY((t), (i))->size))
 
 /**
@@ -584,27 +606,27 @@ struct topa {
 static struct topa *topa_alloc(int cpu, gfp_t gfp)
 {
 	int node = cpu_to_node(cpu);
-	struct topa *topa;
+	struct topa_page *tp;
 	struct page *p;
 
 	p = alloc_pages_node(node, gfp | __GFP_ZERO, 0);
 	if (!p)
 		return NULL;
 
-	topa = page_address(p);
-	topa->last = 0;
-	topa->phys = page_to_phys(p);
+	tp = page_address(p);
+	tp->topa.last = 0;
+	tp->topa.phys = page_to_phys(p);
 
 	/*
 	 * In case of singe-entry ToPA, always put the self-referencing END
 	 * link as the 2nd entry in the table
 	 */
 	if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries)) {
-		TOPA_ENTRY(topa, 1)->base = topa->phys >> TOPA_SHIFT;
-		TOPA_ENTRY(topa, 1)->end = 1;
+		TOPA_ENTRY(&tp->topa, 1)->base = tp->topa.phys;
+		TOPA_ENTRY(&tp->topa, 1)->end = 1;
 	}
 
-	return topa;
+	return &tp->topa;
 }
 
 /**
@@ -714,22 +736,23 @@ static void pt_topa_dump(struct pt_buffer *buf)
 	struct topa *topa;
 
 	list_for_each_entry(topa, &buf->tables, list) {
+		struct topa_page *tp = topa_to_page(topa);
 		int i;
 
-		pr_debug("# table @%p (%016Lx), off %llx size %zx\n", topa->table,
+		pr_debug("# table @%p (%016Lx), off %llx size %zx\n", tp->table,
 			 topa->phys, topa->offset, topa->size);
 		for (i = 0; i < TENTS_PER_PAGE; i++) {
 			pr_debug("# entry @%p (%lx sz %u %c%c%c) raw=%16llx\n",
-				 &topa->table[i],
-				 (unsigned long)topa->table[i].base << TOPA_SHIFT,
-				 sizes(topa->table[i].size),
-				 topa->table[i].end ?  'E' : ' ',
-				 topa->table[i].intr ? 'I' : ' ',
-				 topa->table[i].stop ? 'S' : ' ',
-				 *(u64 *)&topa->table[i]);
+				 &tp->table[i],
+				 (unsigned long)tp->table[i].base << TOPA_SHIFT,
+				 sizes(tp->table[i].size),
+				 tp->table[i].end ?  'E' : ' ',
+				 tp->table[i].intr ? 'I' : ' ',
+				 tp->table[i].stop ? 'S' : ' ',
+				 *(u64 *)&tp->table[i]);
 			if ((intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries) &&
-			     topa->table[i].stop) ||
-			    topa->table[i].end)
+			     tp->table[i].stop) ||
+			    tp->table[i].end)
 				break;
 		}
 	}
@@ -792,7 +815,7 @@ static void pt_update_head(struct pt *pt)
  */
 static void *pt_buffer_region(struct pt_buffer *buf)
 {
-	return phys_to_virt(buf->cur->table[buf->cur_idx].base << TOPA_SHIFT);
+	return phys_to_virt(TOPA_ENTRY(buf->cur, buf->cur_idx)->base << TOPA_SHIFT);
 }
 
 /**
@@ -869,9 +892,11 @@ static void pt_handle_status(struct pt *pt)
 static void pt_read_offset(struct pt_buffer *buf)
 {
 	u64 offset, base_topa;
+	struct topa_page *tp;
 
 	rdmsrl(MSR_IA32_RTIT_OUTPUT_BASE, base_topa);
-	buf->cur = phys_to_virt(base_topa);
+	tp = phys_to_virt(base_topa);
+	buf->cur = &tp->topa;
 
 	rdmsrl(MSR_IA32_RTIT_OUTPUT_MASK, offset);
 	/* offset within current output region */
@@ -1021,6 +1046,7 @@ static void pt_buffer_setup_topa_index(struct pt_buffer *buf)
  */
 static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head)
 {
+	struct topa_page *cur_tp;
 	int pg;
 
 	if (buf->snapshot)
@@ -1029,7 +1055,8 @@ static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head)
 	pg = (head >> PAGE_SHIFT) & (buf->nr_pages - 1);
 	pg = pt_topa_next_entry(buf, pg);
 
-	buf->cur = (struct topa *)((unsigned long)buf->topa_index[pg] & PAGE_MASK);
+	cur_tp = topa_entry_to_page(buf->topa_index[pg]);
+	buf->cur = &cur_tp->topa;
 	buf->cur_idx = buf->topa_index[pg] - TOPA_ENTRY(buf->cur, 0);
 	buf->output_off = head & (pt_buffer_region_size(buf) - 1);
 
@@ -1294,7 +1321,7 @@ void intel_pt_interrupt(void)
 			return;
 		}
 
-		pt_config_buffer(buf->cur->table, buf->cur_idx,
+		pt_config_buffer(topa_to_page(buf->cur)->table, buf->cur_idx,
 				 buf->output_off);
 		pt_config(event);
 	}
@@ -1359,7 +1386,7 @@ static void pt_event_start(struct perf_event *event, int mode)
 	WRITE_ONCE(pt->handle_nmi, 1);
 	hwc->state = 0;
 
-	pt_config_buffer(buf->cur->table, buf->cur_idx,
+	pt_config_buffer(topa_to_page(buf->cur)->table, buf->cur_idx,
 			 buf->output_off);
 	pt_config(event);
 

[PATCH v0 5/6] perf/x86/intel/pt: Free up space in a ToPA descriptor

[Alexander Shishkin]

Currently, we're storing physical address of a ToPA table in its
descriptor, which is completely unnecessary. Since the descriptor
and the table itself share the same page, reducing the descriptor
size leaves more space for the table.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
 arch/x86/events/intel/pt.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index e7b0f8f4f1b0..5965e9493c8b 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -548,14 +548,12 @@ static void pt_config_buffer(void *buf, unsigned int topa_idx,
 /**
  * struct topa - ToPA metadata
  * @list:	linkage to struct pt_buffer's list of tables
- * @phys:	physical address of this page
  * @offset:	offset of the first entry in this table in the buffer
  * @size:	total size of all entries in this table
  * @last:	index of the last initialized entry in this table
  */
 struct topa {
 	struct list_head	list;
-	u64			phys;
 	u64			offset;
 	size_t			size;
 	int			last;
@@ -589,6 +587,11 @@ static inline struct topa_page *topa_entry_to_page(struct topa_entry *te)
 	return (struct topa_page *)((unsigned long)te & PAGE_MASK);
 }
 
+static inline phys_addr_t topa_pfn(struct topa *topa)
+{
+	return PFN_DOWN(virt_to_phys(topa_to_page(topa)));
+}
+
 /* make -1 stand for the last table entry */
 #define TOPA_ENTRY(t, i)				\
 	((i) == -1					\
@@ -615,14 +618,13 @@ static struct topa *topa_alloc(int cpu, gfp_t gfp)
 
 	tp = page_address(p);
 	tp->topa.last = 0;
-	tp->topa.phys = page_to_phys(p);
 
 	/*
 	 * In case of singe-entry ToPA, always put the self-referencing END
 	 * link as the 2nd entry in the table
 	 */
 	if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries)) {
-		TOPA_ENTRY(&tp->topa, 1)->base = tp->topa.phys;
+		TOPA_ENTRY(&tp->topa, 1)->base = page_to_phys(p);
 		TOPA_ENTRY(&tp->topa, 1)->end = 1;
 	}
 
@@ -666,7 +668,7 @@ static void topa_insert_table(struct pt_buffer *buf, struct topa *topa)
 
 	BUG_ON(last->last != TENTS_PER_PAGE - 1);
 
-	TOPA_ENTRY(last, -1)->base = topa->phys >> TOPA_SHIFT;
+	TOPA_ENTRY(last, -1)->base = topa_pfn(topa);
 	TOPA_ENTRY(last, -1)->end = 1;
 }
 
@@ -739,8 +741,8 @@ static void pt_topa_dump(struct pt_buffer *buf)
 		struct topa_page *tp = topa_to_page(topa);
 		int i;
 
-		pr_debug("# table @%p (%016Lx), off %llx size %zx\n", tp->table,
-			 topa->phys, topa->offset, topa->size);
+		pr_debug("# table @%p, off %llx size %zx\n", tp->table,
+			 topa->offset, topa->size);
 		for (i = 0; i < TENTS_PER_PAGE; i++) {
 			pr_debug("# entry @%p (%lx sz %u %c%c%c) raw=%16llx\n",
 				 &tp->table[i],
@@ -1111,7 +1113,7 @@ static int pt_buffer_init_topa(struct pt_buffer *buf, int cpu,
 
 	/* link last table to the first one, unless we're double buffering */
 	if (intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries)) {
-		TOPA_ENTRY(buf->last, -1)->base = buf->first->phys >> TOPA_SHIFT;
+		TOPA_ENTRY(buf->last, -1)->base = topa_pfn(buf->first);
 		TOPA_ENTRY(buf->last, -1)->end = 1;
 	}
 
-- 
2.23.0.rc1

[tip: perf/core] perf/x86/intel/pt: Free up space in a ToPA descriptor

[tip-bot2 for Alexander Shishkin]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     91feca5e2ecc9752894d57c9a72c2645471929c3
Gitweb:        https://git.kernel.org/tip/91feca5e2ecc9752894d57c9a72c2645471929c3
Author:        Alexander Shishkin <alexander.shishkin@linux.intel.com>
AuthorDate:    Wed, 21 Aug 2019 15:47:26 +03:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 26 Aug 2019 12:00:15 +02:00

perf/x86/intel/pt: Free up space in a ToPA descriptor

Currently, we're storing physical address of a ToPA table in its
descriptor, which is completely unnecessary. Since the descriptor
and the table itself share the same page, reducing the descriptor
size leaves more space for the table.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/20190821124727.73310-6-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/events/intel/pt.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index 2e3f068..0f38ed3 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -548,14 +548,12 @@ static void pt_config_buffer(void *buf, unsigned int topa_idx,
 /**
  * struct topa - ToPA metadata
  * @list:	linkage to struct pt_buffer's list of tables
- * @phys:	physical address of this page
  * @offset:	offset of the first entry in this table in the buffer
  * @size:	total size of all entries in this table
  * @last:	index of the last initialized entry in this table
  */
 struct topa {
 	struct list_head	list;
-	u64			phys;
 	u64			offset;
 	size_t			size;
 	int			last;
@@ -589,6 +587,11 @@ static inline struct topa_page *topa_entry_to_page(struct topa_entry *te)
 	return (struct topa_page *)((unsigned long)te & PAGE_MASK);
 }
 
+static inline phys_addr_t topa_pfn(struct topa *topa)
+{
+	return PFN_DOWN(virt_to_phys(topa_to_page(topa)));
+}
+
 /* make -1 stand for the last table entry */
 #define TOPA_ENTRY(t, i)				\
 	((i) == -1					\
@@ -615,14 +618,13 @@ static struct topa *topa_alloc(int cpu, gfp_t gfp)
 
 	tp = page_address(p);
 	tp->topa.last = 0;
-	tp->topa.phys = page_to_phys(p);
 
 	/*
 	 * In case of singe-entry ToPA, always put the self-referencing END
 	 * link as the 2nd entry in the table
 	 */
 	if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries)) {
-		TOPA_ENTRY(&tp->topa, 1)->base = tp->topa.phys;
+		TOPA_ENTRY(&tp->topa, 1)->base = page_to_phys(p);
 		TOPA_ENTRY(&tp->topa, 1)->end = 1;
 	}
 
@@ -666,7 +668,7 @@ static void topa_insert_table(struct pt_buffer *buf, struct topa *topa)
 
 	BUG_ON(last->last != TENTS_PER_PAGE - 1);
 
-	TOPA_ENTRY(last, -1)->base = topa->phys >> TOPA_SHIFT;
+	TOPA_ENTRY(last, -1)->base = topa_pfn(topa);
 	TOPA_ENTRY(last, -1)->end = 1;
 }
 
@@ -739,8 +741,8 @@ static void pt_topa_dump(struct pt_buffer *buf)
 		struct topa_page *tp = topa_to_page(topa);
 		int i;
 
-		pr_debug("# table @%p (%016Lx), off %llx size %zx\n", tp->table,
-			 topa->phys, topa->offset, topa->size);
+		pr_debug("# table @%p, off %llx size %zx\n", tp->table,
+			 topa->offset, topa->size);
 		for (i = 0; i < TENTS_PER_PAGE; i++) {
 			pr_debug("# entry @%p (%lx sz %u %c%c%c) raw=%16llx\n",
 				 &tp->table[i],
@@ -1111,7 +1113,7 @@ static int pt_buffer_init_topa(struct pt_buffer *buf, int cpu,
 
 	/* link last table to the first one, unless we're double buffering */
 	if (intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries)) {
-		TOPA_ENTRY(buf->last, -1)->base = buf->first->phys >> TOPA_SHIFT;
+		TOPA_ENTRY(buf->last, -1)->base = topa_pfn(buf->first);
 		TOPA_ENTRY(buf->last, -1)->end = 1;
 	}
 

[PATCH v0 6/6] perf/x86/intel/pt: Get rid of reverse lookup table for ToPA

[Alexander Shishkin]

In order to quickly find a ToPA entry by its page offset in the buffer,
we're using a reverse lookup table. The problem with it is that it's a
large array of mostly similar pointers, especially so now that we're
using high order allocations from the page allocator. Because its size
is limited to whatever is the maximum for kmalloc(), it places a limit
on the number of ToPA entries per buffer, and therefore, on the total
buffer size, which otherwise doesn't have to be there.

Replace the reverse lookup table with a simple runtime lookup. With the
high order AUX allocations in place, the runtime penalty of such a lookup
is much smaller and in cases where all entries in a ToPA table are of
the same size, the complexity is O(1).

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
 arch/x86/events/intel/pt.c | 194 ++++++++++++++++++++++++-------------
 arch/x86/events/intel/pt.h |  10 +-
 2 files changed, 131 insertions(+), 73 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index 5965e9493c8b..4972c727d5c5 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -551,12 +551,14 @@ static void pt_config_buffer(void *buf, unsigned int topa_idx,
  * @offset:	offset of the first entry in this table in the buffer
  * @size:	total size of all entries in this table
  * @last:	index of the last initialized entry in this table
+ * @z_count:	how many times the first entry repeats
  */
 struct topa {
 	struct list_head	list;
 	u64			offset;
 	size_t			size;
 	int			last;
+	unsigned int		z_count;
 };
 
 /*
@@ -598,6 +600,7 @@ static inline phys_addr_t topa_pfn(struct topa *topa)
 		? &topa_to_page(t)->table[(t)->last]	\
 		: &topa_to_page(t)->table[(i)])
 #define TOPA_ENTRY_SIZE(t, i) (sizes(TOPA_ENTRY((t), (i))->size))
+#define TOPA_ENTRY_PAGES(t, i) (1 << TOPA_ENTRY((t), (i))->size)
 
 /**
  * topa_alloc() - allocate page-sized ToPA table
@@ -713,6 +716,11 @@ static int topa_insert_pages(struct pt_buffer *buf, int cpu, gfp_t gfp)
 		topa_insert_table(buf, topa);
 	}
 
+	if (topa->z_count == topa->last - 1) {
+		if (order == TOPA_ENTRY(topa, topa->last - 1)->size)
+			topa->z_count++;
+	}
+
 	TOPA_ENTRY(topa, -1)->base = page_to_phys(p) >> TOPA_SHIFT;
 	TOPA_ENTRY(topa, -1)->size = order;
 	if (!buf->snapshot &&
@@ -756,6 +764,8 @@ static void pt_topa_dump(struct pt_buffer *buf)
 			     tp->table[i].stop) ||
 			    tp->table[i].end)
 				break;
+			if (!i && topa->z_count)
+				i += topa->z_count;
 		}
 	}
 }
@@ -907,29 +917,97 @@ static void pt_read_offset(struct pt_buffer *buf)
 	buf->cur_idx = (offset & 0xffffff80) >> 7;
 }
 
-/**
- * pt_topa_next_entry() - obtain index of the first page in the next ToPA entry
- * @buf:	PT buffer.
- * @pg:		Page offset in the buffer.
- *
- * When advancing to the next output region (ToPA entry), given a page offset
- * into the buffer, we need to find the offset of the first page in the next
- * region.
- */
-static unsigned int pt_topa_next_entry(struct pt_buffer *buf, unsigned int pg)
+static struct topa_entry *
+pt_topa_entry_for_page(struct pt_buffer *buf, unsigned int pg)
+{
+	struct topa_page *tp;
+	struct topa *topa;
+	unsigned int idx, cur_pg = 0, z_pg = 0, start_idx = 0;
+
+	/*
+	 * Indicates a bug in the caller.
+	 */
+	if (WARN_ON_ONCE(pg >= buf->nr_pages))
+		return NULL;
+
+	/*
+	 * First, find the ToPA table where @pg fits. With high
+	 * order allocations, there shouldn't be many of these.
+	 */
+	list_for_each_entry(topa, &buf->tables, list) {
+		if (topa->offset + topa->size > pg << PAGE_SHIFT)
+			goto found;
+	}
+
+	/*
+	 * Hitting this means we have a problem in the ToPA
+	 * allocation code.
+	 */
+	WARN_ON_ONCE(1);
+
+	return NULL;
+
+found:
+	/*
+	 * Indicates a problem in the ToPA allocation code.
+	 */
+	if (WARN_ON_ONCE(topa->last == -1))
+		return NULL;
+
+	tp = topa_to_page(topa);
+	cur_pg = PFN_DOWN(topa->offset);
+	if (topa->z_count) {
+		z_pg = TOPA_ENTRY_PAGES(topa, 0) * (topa->z_count + 1);
+		start_idx = topa->z_count + 1;
+	}
+
+	/*
+	 * Multiple entries at the beginning of the table have the same size,
+	 * ideally all of them; if @pg falls there, the search is done.
+	 */
+	if (pg >= cur_pg && pg < cur_pg + z_pg) {
+		idx = (pg - cur_pg) / TOPA_ENTRY_PAGES(topa, 0);
+		return &tp->table[idx];
+	}
+
+	/*
+	 * Otherwise, slow path: iterate through the remaining entries.
+	 */
+	for (idx = start_idx, cur_pg += z_pg; idx < topa->last; idx++) {
+		if (cur_pg + TOPA_ENTRY_PAGES(topa, idx) > pg)
+			return &tp->table[idx];
+
+		cur_pg += TOPA_ENTRY_PAGES(topa, idx);
+	}
+
+	/*
+	 * Means we couldn't find a ToPA entry in the table that does match.
+	 */
+	WARN_ON_ONCE(1);
+
+	return NULL;
+}
+
+static struct topa_entry *
+pt_topa_prev_entry(struct pt_buffer *buf, struct topa_entry *te)
 {
-	struct topa_entry *te = buf->topa_index[pg];
+	unsigned long table = (unsigned long)te & ~(PAGE_SIZE - 1);
+	struct topa_page *tp;
+	struct topa *topa;
 
-	/* one region */
-	if (buf->first == buf->last && buf->first->last == 1)
-		return pg;
+	tp = (struct topa_page *)table;
+	if (tp->table != te)
+		return --te;
+
+	topa = &tp->topa;
+	if (topa == buf->first)
+		topa = buf->last;
+	else
+		topa = list_prev_entry(topa, list);
 
-	do {
-		pg++;
-		pg &= buf->nr_pages - 1;
-	} while (buf->topa_index[pg] == te);
+	tp = topa_to_page(topa);
 
-	return pg;
+	return &tp->table[topa->last - 1];
 }
 
 /**
@@ -964,9 +1042,13 @@ static int pt_buffer_reset_markers(struct pt_buffer *buf,
 		return 0;
 
 	/* clear STOP and INT from current entry */
-	buf->topa_index[buf->stop_pos]->stop = 0;
-	buf->topa_index[buf->stop_pos]->intr = 0;
-	buf->topa_index[buf->intr_pos]->intr = 0;
+	if (buf->stop_te) {
+		buf->stop_te->stop = 0;
+		buf->stop_te->intr = 0;
+	}
+
+	if (buf->intr_te)
+		buf->intr_te->intr = 0;
 
 	/* how many pages till the STOP marker */
 	npages = handle->size >> PAGE_SHIFT;
@@ -977,7 +1059,12 @@ static int pt_buffer_reset_markers(struct pt_buffer *buf,
 
 	idx = (head >> PAGE_SHIFT) + npages;
 	idx &= buf->nr_pages - 1;
-	buf->stop_pos = idx;
+
+	if (idx != buf->stop_pos) {
+		buf->stop_pos = idx;
+		buf->stop_te = pt_topa_entry_for_page(buf, idx);
+		buf->stop_te = pt_topa_prev_entry(buf, buf->stop_te);
+	}
 
 	wakeup = handle->wakeup >> PAGE_SHIFT;
 
@@ -987,50 +1074,19 @@ static int pt_buffer_reset_markers(struct pt_buffer *buf,
 		idx = wakeup;
 
 	idx &= buf->nr_pages - 1;
-	buf->intr_pos = idx;
+	if (idx != buf->intr_pos) {
+		buf->intr_pos = idx;
+		buf->intr_te = pt_topa_entry_for_page(buf, idx);
+		buf->intr_te = pt_topa_prev_entry(buf, buf->intr_te);
+	}
 
-	buf->topa_index[buf->stop_pos]->stop = 1;
-	buf->topa_index[buf->stop_pos]->intr = 1;
-	buf->topa_index[buf->intr_pos]->intr = 1;
+	buf->stop_te->stop = 1;
+	buf->stop_te->intr = 1;
+	buf->intr_te->intr = 1;
 
 	return 0;
 }
 
-/**
- * pt_buffer_setup_topa_index() - build topa_index[] table of regions
- * @buf:	PT buffer.
- *
- * topa_index[] references output regions indexed by offset into the
- * buffer for purposes of quick reverse lookup.
- */
-static void pt_buffer_setup_topa_index(struct pt_buffer *buf)
-{
-	struct topa *cur = buf->first, *prev = buf->last;
-	struct topa_entry *te_cur = TOPA_ENTRY(cur, 0),
-		*te_prev = TOPA_ENTRY(prev, prev->last - 1);
-	int pg = 0, idx = 0;
-
-	while (pg < buf->nr_pages) {
-		int tidx;
-
-		/* pages within one topa entry */
-		for (tidx = 0; tidx < 1 << te_cur->size; tidx++, pg++)
-			buf->topa_index[pg] = te_prev;
-
-		te_prev = te_cur;
-
-		if (idx == cur->last - 1) {
-			/* advance to next topa table */
-			idx = 0;
-			cur = list_entry(cur->list.next, struct topa, list);
-		} else {
-			idx++;
-		}
-		te_cur = TOPA_ENTRY(cur, idx);
-	}
-
-}
-
 /**
  * pt_buffer_reset_offsets() - adjust buffer's write pointers from aux_head
  * @buf:	PT buffer.
@@ -1049,17 +1105,18 @@ static void pt_buffer_setup_topa_index(struct pt_buffer *buf)
 static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head)
 {
 	struct topa_page *cur_tp;
+	struct topa_entry *te;
 	int pg;
 
 	if (buf->snapshot)
 		head &= (buf->nr_pages << PAGE_SHIFT) - 1;
 
 	pg = (head >> PAGE_SHIFT) & (buf->nr_pages - 1);
-	pg = pt_topa_next_entry(buf, pg);
+	te = pt_topa_entry_for_page(buf, pg);
 
-	cur_tp = topa_entry_to_page(buf->topa_index[pg]);
+	cur_tp = topa_entry_to_page(te);
 	buf->cur = &cur_tp->topa;
-	buf->cur_idx = buf->topa_index[pg] - TOPA_ENTRY(buf->cur, 0);
+	buf->cur_idx = te - TOPA_ENTRY(buf->cur, 0);
 	buf->output_off = head & (pt_buffer_region_size(buf) - 1);
 
 	local64_set(&buf->head, head);
@@ -1109,8 +1166,6 @@ static int pt_buffer_init_topa(struct pt_buffer *buf, int cpu,
 		}
 	}
 
-	pt_buffer_setup_topa_index(buf);
-
 	/* link last table to the first one, unless we're double buffering */
 	if (intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries)) {
 		TOPA_ENTRY(buf->last, -1)->base = topa_pfn(buf->first);
@@ -1147,13 +1202,14 @@ pt_buffer_setup_aux(struct perf_event *event, void **pages,
 		cpu = raw_smp_processor_id();
 	node = cpu_to_node(cpu);
 
-	buf = kzalloc_node(offsetof(struct pt_buffer, topa_index[nr_pages]),
-			   GFP_KERNEL, node);
+	buf = kzalloc_node(sizeof(struct pt_buffer), GFP_KERNEL, node);
 	if (!buf)
 		return NULL;
 
 	buf->snapshot = snapshot;
 	buf->data_pages = pages;
+	buf->stop_pos = -1;
+	buf->intr_pos = -1;
 
 	INIT_LIST_HEAD(&buf->tables);
 
diff --git a/arch/x86/events/intel/pt.h b/arch/x86/events/intel/pt.h
index 8de8ed089697..1d2bb7572374 100644
--- a/arch/x86/events/intel/pt.h
+++ b/arch/x86/events/intel/pt.h
@@ -64,8 +64,10 @@ struct pt_pmu {
  * @lost:	if data was lost/truncated
  * @head:	logical write offset inside the buffer
  * @snapshot:	if this is for a snapshot/overwrite counter
- * @stop_pos:	STOP topa entry in the buffer
- * @intr_pos:	INT topa entry in the buffer
+ * @stop_pos:	STOP topa entry index
+ * @intr_pos:	INT topa entry index
+ * @stop_te:	STOP topa entry pointer
+ * @intr_te:	INT topa entry pointer
  * @data_pages:	array of pages from perf
  * @topa_index:	table of topa entries indexed by page offset
  */
@@ -78,9 +80,9 @@ struct pt_buffer {
 	local_t			data_size;
 	local64_t		head;
 	bool			snapshot;
-	unsigned long		stop_pos, intr_pos;
+	long			stop_pos, intr_pos;
+	struct topa_entry	*stop_te, *intr_te;
 	void			**data_pages;
-	struct topa_entry	*topa_index[0];
 };
 
 #define PT_FILTERS_NUM	4
-- 
2.23.0.rc1

[tip: perf/core] perf/x86/intel/pt: Get rid of reverse lookup table for ToPA

[tip-bot2 for Alexander Shishkin]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     39152ee51b77851689f9b23fde6f610d13566c39
Gitweb:        https://git.kernel.org/tip/39152ee51b77851689f9b23fde6f610d13566c39
Author:        Alexander Shishkin <alexander.shishkin@linux.intel.com>
AuthorDate:    Wed, 21 Aug 2019 15:47:27 +03:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 26 Aug 2019 12:00:16 +02:00

perf/x86/intel/pt: Get rid of reverse lookup table for ToPA

In order to quickly find a ToPA entry by its page offset in the buffer,
we're using a reverse lookup table. The problem with it is that it's a
large array of mostly similar pointers, especially so now that we're
using high order allocations from the page allocator. Because its size
is limited to whatever is the maximum for kmalloc(), it places a limit
on the number of ToPA entries per buffer, and therefore, on the total
buffer size, which otherwise doesn't have to be there.

Replace the reverse lookup table with a simple runtime lookup. With the
high order AUX allocations in place, the runtime penalty of such a lookup
is much smaller and in cases where all entries in a ToPA table are of
the same size, the complexity is O(1).

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/20190821124727.73310-7-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/events/intel/pt.c | 194 +++++++++++++++++++++++-------------
 arch/x86/events/intel/pt.h |  10 +-
 2 files changed, 131 insertions(+), 73 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index 0f38ed3..fa43d90 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -551,12 +551,14 @@ static void pt_config_buffer(void *buf, unsigned int topa_idx,
  * @offset:	offset of the first entry in this table in the buffer
  * @size:	total size of all entries in this table
  * @last:	index of the last initialized entry in this table
+ * @z_count:	how many times the first entry repeats
  */
 struct topa {
 	struct list_head	list;
 	u64			offset;
 	size_t			size;
 	int			last;
+	unsigned int		z_count;
 };
 
 /*
@@ -598,6 +600,7 @@ static inline phys_addr_t topa_pfn(struct topa *topa)
 		? &topa_to_page(t)->table[(t)->last]	\
 		: &topa_to_page(t)->table[(i)])
 #define TOPA_ENTRY_SIZE(t, i) (sizes(TOPA_ENTRY((t), (i))->size))
+#define TOPA_ENTRY_PAGES(t, i) (1 << TOPA_ENTRY((t), (i))->size)
 
 /**
  * topa_alloc() - allocate page-sized ToPA table
@@ -713,6 +716,11 @@ static int topa_insert_pages(struct pt_buffer *buf, int cpu, gfp_t gfp)
 		topa_insert_table(buf, topa);
 	}
 
+	if (topa->z_count == topa->last - 1) {
+		if (order == TOPA_ENTRY(topa, topa->last - 1)->size)
+			topa->z_count++;
+	}
+
 	TOPA_ENTRY(topa, -1)->base = page_to_phys(p) >> TOPA_SHIFT;
 	TOPA_ENTRY(topa, -1)->size = order;
 	if (!buf->snapshot &&
@@ -756,6 +764,8 @@ static void pt_topa_dump(struct pt_buffer *buf)
 			     tp->table[i].stop) ||
 			    tp->table[i].end)
 				break;
+			if (!i && topa->z_count)
+				i += topa->z_count;
 		}
 	}
 }
@@ -907,29 +917,97 @@ static void pt_read_offset(struct pt_buffer *buf)
 	buf->cur_idx = (offset & 0xffffff80) >> 7;
 }
 
-/**
- * pt_topa_next_entry() - obtain index of the first page in the next ToPA entry
- * @buf:	PT buffer.
- * @pg:		Page offset in the buffer.
- *
- * When advancing to the next output region (ToPA entry), given a page offset
- * into the buffer, we need to find the offset of the first page in the next
- * region.
- */
-static unsigned int pt_topa_next_entry(struct pt_buffer *buf, unsigned int pg)
+static struct topa_entry *
+pt_topa_entry_for_page(struct pt_buffer *buf, unsigned int pg)
+{
+	struct topa_page *tp;
+	struct topa *topa;
+	unsigned int idx, cur_pg = 0, z_pg = 0, start_idx = 0;
+
+	/*
+	 * Indicates a bug in the caller.
+	 */
+	if (WARN_ON_ONCE(pg >= buf->nr_pages))
+		return NULL;
+
+	/*
+	 * First, find the ToPA table where @pg fits. With high
+	 * order allocations, there shouldn't be many of these.
+	 */
+	list_for_each_entry(topa, &buf->tables, list) {
+		if (topa->offset + topa->size > pg << PAGE_SHIFT)
+			goto found;
+	}
+
+	/*
+	 * Hitting this means we have a problem in the ToPA
+	 * allocation code.
+	 */
+	WARN_ON_ONCE(1);
+
+	return NULL;
+
+found:
+	/*
+	 * Indicates a problem in the ToPA allocation code.
+	 */
+	if (WARN_ON_ONCE(topa->last == -1))
+		return NULL;
+
+	tp = topa_to_page(topa);
+	cur_pg = PFN_DOWN(topa->offset);
+	if (topa->z_count) {
+		z_pg = TOPA_ENTRY_PAGES(topa, 0) * (topa->z_count + 1);
+		start_idx = topa->z_count + 1;
+	}
+
+	/*
+	 * Multiple entries at the beginning of the table have the same size,
+	 * ideally all of them; if @pg falls there, the search is done.
+	 */
+	if (pg >= cur_pg && pg < cur_pg + z_pg) {
+		idx = (pg - cur_pg) / TOPA_ENTRY_PAGES(topa, 0);
+		return &tp->table[idx];
+	}
+
+	/*
+	 * Otherwise, slow path: iterate through the remaining entries.
+	 */
+	for (idx = start_idx, cur_pg += z_pg; idx < topa->last; idx++) {
+		if (cur_pg + TOPA_ENTRY_PAGES(topa, idx) > pg)
+			return &tp->table[idx];
+
+		cur_pg += TOPA_ENTRY_PAGES(topa, idx);
+	}
+
+	/*
+	 * Means we couldn't find a ToPA entry in the table that does match.
+	 */
+	WARN_ON_ONCE(1);
+
+	return NULL;
+}
+
+static struct topa_entry *
+pt_topa_prev_entry(struct pt_buffer *buf, struct topa_entry *te)
 {
-	struct topa_entry *te = buf->topa_index[pg];
+	unsigned long table = (unsigned long)te & ~(PAGE_SIZE - 1);
+	struct topa_page *tp;
+	struct topa *topa;
 
-	/* one region */
-	if (buf->first == buf->last && buf->first->last == 1)
-		return pg;
+	tp = (struct topa_page *)table;
+	if (tp->table != te)
+		return --te;
+
+	topa = &tp->topa;
+	if (topa == buf->first)
+		topa = buf->last;
+	else
+		topa = list_prev_entry(topa, list);
 
-	do {
-		pg++;
-		pg &= buf->nr_pages - 1;
-	} while (buf->topa_index[pg] == te);
+	tp = topa_to_page(topa);
 
-	return pg;
+	return &tp->table[topa->last - 1];
 }
 
 /**
@@ -964,9 +1042,13 @@ static int pt_buffer_reset_markers(struct pt_buffer *buf,
 		return 0;
 
 	/* clear STOP and INT from current entry */
-	buf->topa_index[buf->stop_pos]->stop = 0;
-	buf->topa_index[buf->stop_pos]->intr = 0;
-	buf->topa_index[buf->intr_pos]->intr = 0;
+	if (buf->stop_te) {
+		buf->stop_te->stop = 0;
+		buf->stop_te->intr = 0;
+	}
+
+	if (buf->intr_te)
+		buf->intr_te->intr = 0;
 
 	/* how many pages till the STOP marker */
 	npages = handle->size >> PAGE_SHIFT;
@@ -977,7 +1059,12 @@ static int pt_buffer_reset_markers(struct pt_buffer *buf,
 
 	idx = (head >> PAGE_SHIFT) + npages;
 	idx &= buf->nr_pages - 1;
-	buf->stop_pos = idx;
+
+	if (idx != buf->stop_pos) {
+		buf->stop_pos = idx;
+		buf->stop_te = pt_topa_entry_for_page(buf, idx);
+		buf->stop_te = pt_topa_prev_entry(buf, buf->stop_te);
+	}
 
 	wakeup = handle->wakeup >> PAGE_SHIFT;
 
@@ -987,51 +1074,20 @@ static int pt_buffer_reset_markers(struct pt_buffer *buf,
 		idx = wakeup;
 
 	idx &= buf->nr_pages - 1;
-	buf->intr_pos = idx;
+	if (idx != buf->intr_pos) {
+		buf->intr_pos = idx;
+		buf->intr_te = pt_topa_entry_for_page(buf, idx);
+		buf->intr_te = pt_topa_prev_entry(buf, buf->intr_te);
+	}
 
-	buf->topa_index[buf->stop_pos]->stop = 1;
-	buf->topa_index[buf->stop_pos]->intr = 1;
-	buf->topa_index[buf->intr_pos]->intr = 1;
+	buf->stop_te->stop = 1;
+	buf->stop_te->intr = 1;
+	buf->intr_te->intr = 1;
 
 	return 0;
 }
 
 /**
- * pt_buffer_setup_topa_index() - build topa_index[] table of regions
- * @buf:	PT buffer.
- *
- * topa_index[] references output regions indexed by offset into the
- * buffer for purposes of quick reverse lookup.
- */
-static void pt_buffer_setup_topa_index(struct pt_buffer *buf)
-{
-	struct topa *cur = buf->first, *prev = buf->last;
-	struct topa_entry *te_cur = TOPA_ENTRY(cur, 0),
-		*te_prev = TOPA_ENTRY(prev, prev->last - 1);
-	int pg = 0, idx = 0;
-
-	while (pg < buf->nr_pages) {
-		int tidx;
-
-		/* pages within one topa entry */
-		for (tidx = 0; tidx < 1 << te_cur->size; tidx++, pg++)
-			buf->topa_index[pg] = te_prev;
-
-		te_prev = te_cur;
-
-		if (idx == cur->last - 1) {
-			/* advance to next topa table */
-			idx = 0;
-			cur = list_entry(cur->list.next, struct topa, list);
-		} else {
-			idx++;
-		}
-		te_cur = TOPA_ENTRY(cur, idx);
-	}
-
-}
-
-/**
  * pt_buffer_reset_offsets() - adjust buffer's write pointers from aux_head
  * @buf:	PT buffer.
  * @head:	Write pointer (aux_head) from AUX buffer.
@@ -1049,17 +1105,18 @@ static void pt_buffer_setup_topa_index(struct pt_buffer *buf)
 static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head)
 {
 	struct topa_page *cur_tp;
+	struct topa_entry *te;
 	int pg;
 
 	if (buf->snapshot)
 		head &= (buf->nr_pages << PAGE_SHIFT) - 1;
 
 	pg = (head >> PAGE_SHIFT) & (buf->nr_pages - 1);
-	pg = pt_topa_next_entry(buf, pg);
+	te = pt_topa_entry_for_page(buf, pg);
 
-	cur_tp = topa_entry_to_page(buf->topa_index[pg]);
+	cur_tp = topa_entry_to_page(te);
 	buf->cur = &cur_tp->topa;
-	buf->cur_idx = buf->topa_index[pg] - TOPA_ENTRY(buf->cur, 0);
+	buf->cur_idx = te - TOPA_ENTRY(buf->cur, 0);
 	buf->output_off = head & (pt_buffer_region_size(buf) - 1);
 
 	local64_set(&buf->head, head);
@@ -1109,8 +1166,6 @@ static int pt_buffer_init_topa(struct pt_buffer *buf, int cpu,
 		}
 	}
 
-	pt_buffer_setup_topa_index(buf);
-
 	/* link last table to the first one, unless we're double buffering */
 	if (intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries)) {
 		TOPA_ENTRY(buf->last, -1)->base = topa_pfn(buf->first);
@@ -1147,13 +1202,14 @@ pt_buffer_setup_aux(struct perf_event *event, void **pages,
 		cpu = raw_smp_processor_id();
 	node = cpu_to_node(cpu);
 
-	buf = kzalloc_node(offsetof(struct pt_buffer, topa_index[nr_pages]),
-			   GFP_KERNEL, node);
+	buf = kzalloc_node(sizeof(struct pt_buffer), GFP_KERNEL, node);
 	if (!buf)
 		return NULL;
 
 	buf->snapshot = snapshot;
 	buf->data_pages = pages;
+	buf->stop_pos = -1;
+	buf->intr_pos = -1;
 
 	INIT_LIST_HEAD(&buf->tables);
 
diff --git a/arch/x86/events/intel/pt.h b/arch/x86/events/intel/pt.h
index 8de8ed0..1d2bb75 100644
--- a/arch/x86/events/intel/pt.h
+++ b/arch/x86/events/intel/pt.h
@@ -64,8 +64,10 @@ struct pt_pmu {
  * @lost:	if data was lost/truncated
  * @head:	logical write offset inside the buffer
  * @snapshot:	if this is for a snapshot/overwrite counter
- * @stop_pos:	STOP topa entry in the buffer
- * @intr_pos:	INT topa entry in the buffer
+ * @stop_pos:	STOP topa entry index
+ * @intr_pos:	INT topa entry index
+ * @stop_te:	STOP topa entry pointer
+ * @intr_te:	INT topa entry pointer
  * @data_pages:	array of pages from perf
  * @topa_index:	table of topa entries indexed by page offset
  */
@@ -78,9 +80,9 @@ struct pt_buffer {
 	local_t			data_size;
 	local64_t		head;
 	bool			snapshot;
-	unsigned long		stop_pos, intr_pos;
+	long			stop_pos, intr_pos;
+	struct topa_entry	*stop_te, *intr_te;
 	void			**data_pages;
-	struct topa_entry	*topa_index[0];
 };
 
 #define PT_FILTERS_NUM	4