Hi Mathieu,

On 14/05/2019 20:40, Mathieu Poirier wrote:

Unify amongst sink drivers how the AUX ring buffer head is communicated to user space. That way the same algorithm in cs_etm_find_snapshot()

I would leave the userspace tool's function name out of the commit description and the comment below. We could instead say: "That way the same algorithm can be used by the userspace tool to determine the position and the size of the latest snapshot data."

can be used to determine where the latest data is and how much of it to access.

Signed-off-by: Mathieu Poirier mathieu.poirier@linaro.org

drivers/hwtracing/coresight/coresight-etb10.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c index 4ee4c80a4354..60e753b1768d 100644 --- a/drivers/hwtracing/coresight/coresight-etb10.c +++ b/drivers/hwtracing/coresight/coresight-etb10.c @@ -548,13 +548,14 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev, writel_relaxed(0x0, drvdata->base + ETB_RAM_WRITE_POINTER); /*

• * In snapshot mode we have to update the handle->head to point
  

• * to the new location.
  

• * In snapshot mode we simply increment the head by the number of byte
  

• * that were written.  User space function  cs_etm_find_snapshot() will
  

• * figure out how many bytes to get from the AUX buffer based on the
  

• * position of the head.
  

  */

• if (buf->snapshot) {

• handle->head = (cur * PAGE_SIZE) + offset;
  

• to_read = buf->nr_pages << PAGE_SHIFT;
  

• }

• if (buf->snapshot)

• handle->head += to_read;
  

• __etb_enable_hw(drvdata); CS_LOCK(drvdata->base); out:

Otherwise:

Reviewed-by: Suzuki K Poulose suzuki.poulose@arm.com

Hi Mathieu,

On 15/05/2019 15:28, Mathieu Poirier wrote:

Good day Suzuki,

On Wed, 15 May 2019 at 03:45, Suzuki K Poulose suzuki.poulose@arm.com wrote:

...

Hi Mathieu,

On 14/05/2019 20:40, Mathieu Poirier wrote:

...

Unify amongst sink drivers how the AUX ring buffer head is communicated to user space. That way the same algorithm in cs_etm_find_snapshot()

I would leave the userspace tool's function name out of the commit description and the comment below. We could instead say: "That way the same algorithm can be used by the userspace tool to determine the position and the size of the latest snapshot data."

I purposely added the name of the function there so that people can quickly find it and avoid any misunderstanding about the code in question. But I also have the same information as a comment in the code, which should be sufficient. I'll fix it.

No need to resend the series as it is just the comment and description. You may fix up both before committing.

...

...

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c index 4ee4c80a4354..60e753b1768d 100644 --- a/drivers/hwtracing/coresight/coresight-etb10.c +++ b/drivers/hwtracing/coresight/coresight-etb10.c @@ -548,13 +548,14 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev, writel_relaxed(0x0, drvdata->base + ETB_RAM_WRITE_POINTER);

   /*

•  * In snapshot mode we have to update the handle->head to point
  

•  * to the new location.
  

•  * In snapshot mode we simply increment the head by the number of byte
  

•  * that were written.  User space function  cs_etm_find_snapshot() will
  

•  * figure out how many bytes to get from the AUX buffer based on the
  

•  * position of the head.
    */
  

• if (buf->snapshot) {
  

•         handle->head = (cur * PAGE_SIZE) + offset;
  

•         to_read = buf->nr_pages << PAGE_SHIFT;
  

• }
  

• if (buf->snapshot)
  

•         handle->head += to_read;
  

•  __etb_enable_hw(drvdata);
   CS_LOCK(drvdata->base);
  

  out:

Otherwise:

Reviewed-by: Suzuki K Poulose suzuki.poulose@arm.com

Is this for all the kernel space patches or just this one?

It was initially for the first patch. But now I realize that all the other patches are of similar approach. I will add a different tag for better tracking.

Cheers Suzuki

On Thu, 16 May 2019 at 09:00, Leo Yan leo.yan@linaro.org wrote:

On Tue, May 14, 2019 at 01:40:18PM -0600, Mathieu Poirier wrote:

...

This patch adds the necessay intelligence to properly compute the value of 'old' and 'head' when operating in snapshot mode. That way we can get the latest information in the AUX buffer and be compatible with the generic AUX ring buffer mechanic.

Signed-off-by: Mathieu Poirier mathieu.poirier@linaro.org

tools/perf/arch/arm/util/cs-etm.c | 124 ++++++++++++++++++++++++++++-- 1 file changed, 119 insertions(+), 5 deletions(-)

diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c index 911426721170..3734e3fd18f8 100644 --- a/tools/perf/arch/arm/util/cs-etm.c +++ b/tools/perf/arch/arm/util/cs-etm.c @@ -31,6 +31,8 @@ struct cs_etm_recording { struct auxtrace_record itr; struct perf_pmu *cs_etm_pmu; struct perf_evlist *evlist;

• int                     wrapped_cnt;
  

• bool                    *wrapped;
  bool                    snapshot_mode;
  size_t                  snapshot_size;
  

}; @@ -536,16 +538,126 @@ static int cs_etm_info_fill(struct auxtrace_record *itr, return 0; }

-static int cs_etm_find_snapshot(struct auxtrace_record *itr __maybe_unused, +static int cs_etm_alloc_wrapped_array(struct cs_etm_recording *ptr, int idx) +{

• bool *wrapped;
  

• int cnt = ptr->wrapped_cnt;
  

• /* Make @ptr->wrapped as big as @idx */
  

• while (cnt <= idx)
  

•         cnt++;
  

• /* Free'ed in cs_etm_recording_free() */
  

• wrapped = reallocarray(ptr->wrapped, cnt, sizeof(bool));
  

• if (!wrapped)
  

•         return -ENOMEM;
  

• ptr->wrapped_cnt = cnt;
  

• ptr->wrapped = wrapped;
  

• return 0;
  

+}

+static bool cs_etm_buffer_has_wrapped(unsigned char *buffer,

•                               size_t buffer_size, u64 head)
  

+{

• u64 i, watermark;
  

• u64 *buf = (u64 *)buffer;
  

• size_t buf_size = buffer_size;
  

• /*
  

•  * We want to look the very last 512 byte (chosen arbitrarily) in
  

•  * the ring buffer.
  

•  */
  

• watermark = buf_size - 512;
  

• /*
  

•  * @head is continuously increasing - if its value is equal or greater
  

•  * than the size of the ring buffer, it has wrapped around.
  

•  */
  

• if (head >= buffer_size)
  

•         return true;
  

• /*
  

•  * The value of @head is somewhere within the size of the ring buffer.
  

•  * This can be that there hasn't been enough data to fill the ring
  

•  * buffer yet or the trace time was so long that @head has numerically
  

•  * wrapped around.  To find we need to check if we have data at the very
  

•  * end of the ring buffer.  We can reliably do this because mmap'ed
  

•  * pages are zeroed out and there is a fresh mapping with every new
  

•  * session.
  

•  */
  

• /* @head is less than 512 byte from the end of the ring buffer */
  

• if (head > watermark)
  

•         watermark = head;
  

• /*
  

•  * Speed things up by using 64 bit transactions (see "u64 *buf" above)
  

•  */
  

• watermark >>= 3;
  

• buf_size >>= 3;
  

• /*
  

•  * If we find trace data at the end of the ring buffer, @head has
  

•  * been there and has numerically wrapped around at least once.
  

•  */
  

• for (i = watermark; i < buf_size; i++)
  

•         if (buf[i])
  

I think here should be: if (buf[i << 3])

It would be if buf[] was a char *, but it is a u64 *.

Otherwise, this patch looks good to me.

...

•                 return true;
  

• return false;
  

+}

+static int cs_etm_find_snapshot(struct auxtrace_record *itr, int idx, struct auxtrace_mmap *mm,

•                         unsigned char *data __maybe_unused,
  

•                         unsigned char *data,
                          u64 *head, u64 *old)
  

{

• pr_debug3("%s: mmap index %d old head %zu new head %zu size %zu\n",
  

• int err;
  

• bool wrapped;
  

• struct cs_etm_recording *ptr =
  

•                 container_of(itr, struct cs_etm_recording, itr);
  

• /*
  

•  * Allocate memory to keep track of wrapping if this is the first
  

•  * time we deal with this *mm.
  

•  */
  

• if (idx >= ptr->wrapped_cnt) {
  

•         err = cs_etm_alloc_wrapped_array(ptr, idx);
  

•         if (err)
  

•                 return err;
  

• }
  

• /*
  

•  * Check to see if *head has wrapped around.  If it hasn't only the
  

•  * amount of data between *head and *old is snapshot'ed to avoid
  

•  * bloating the perf.data file with zeros.  But as soon as *head has
  

•  * wrapped around the entire size of the AUX ring buffer it taken.
  

•  */
  

• wrapped = ptr->wrapped[idx];
  

• if (!wrapped && cs_etm_buffer_has_wrapped(data, mm->len, *head)) {
  

•         wrapped = true;
  

•         ptr->wrapped[idx] = true;
  

• }
  

• pr_debug3("%s: mmap index %d old head %lx new head %lx size %lx\n",
            __func__, idx, (size_t)*old, (size_t)*head, mm->len);
  
  

• *old = *head;
  

• *head += mm->len;
  

• /* No wrap has occurred, we can just use *head and *old. */
  

• if (!wrapped)
  

•         return 0;
  

• /*
  

•  * *head has wrapped around - adjust *head and *old to pickup the
  

•  * entire content of the AUX buffer.
  

•  */
  

• if (*head >= mm->len) {
  

•         *old = *head - mm->len;
  

• } else {
  

•         *head += mm->len;
  

•         *old = *head - mm->len;
  

• }
  
  return 0;
  

} @@ -586,6 +698,8 @@ static void cs_etm_recording_free(struct auxtrace_record *itr) { struct cs_etm_recording *ptr = container_of(itr, struct cs_etm_recording, itr);

• zfree(&ptr->wrapped);
  free(ptr);
  

}

-- 2.17.1