Hi Mathieu, Mark,
On Wed, Feb 13, 2019 at 02:26:25PM -0700, Mathieu Poirier wrote:
Hi Mark,
CoreSight trace collection is broken on v5.0-rc6 due to this commit:
9dff0aa95a32 perf/core: Don't WARN() for impossible ring-buffer sizes
Before: root@juno:/home/linaro# perf record -e cs_etm/@20070000.etr/u --per-thread uname [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.036 MB perf.data ] root@juno:/home/linaro#
After: root@juno:/home/linaro# perf record -e cs_etm/@20070000.etr/u --per-thread uname failed to mmap with 12 (Cannot allocate memory) root@juno:/home/linaro#
The problem is related to the order_base_2() [1] test with a size of 1264, stemming from nr_pages equal to 128. The combination yields an order of 11, something leading directly to the error path.
The results are the same with linux-next 20190213. This was tested on a Juno R0 and R1 with a 4K page configuration. I haven't tried but I'm pretty sure it breaks IntelPT as well.
I noticed in another thread [1] Peter gave out the fixing for this issue; applied this fixing on my local code and it fixes CoreSight tracing issue.
Thanks, Leo Yan