mirror of
https://github.com/torvalds/linux.git
synced 2026-02-04 15:28:49 +08:00
4e8a5c1551
After a discussion with Andi, move the perf_event_attr.precise_ip
detection for maximum precise config (via :P modifier or for default
cycles event) to perf_evsel__open().
The current detection in perf_event_attr__set_max_precise_ip() is
tricky, because precise_ip config is specific for given event and it
currently checks only hw cycles.
We now check for valid precise_ip value right after failing
sys_perf_event_open() for specific event, before any of the
perf_event_attr fallback code gets executed.
This way we get the proper config in perf_event_attr together with
allowed precise_ip settings.
We can see that code activity with -vv, like:
$ perf record -vv ls
...
------------------------------------------------------------
perf_event_attr:
size 112
{ sample_period, sample_freq } 4000
...
precise_ip 3
sample_id_all 1
exclude_guest 1
mmap2 1
comm_exec 1
ksymbol 1
------------------------------------------------------------
sys_perf_event_open: pid 9926 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open failed, error -95
decreasing precise_ip by one (2)
------------------------------------------------------------
perf_event_attr:
size 112
{ sample_period, sample_freq } 4000
...
precise_ip 2
sample_id_all 1
exclude_guest 1
mmap2 1
comm_exec 1
ksymbol 1
------------------------------------------------------------
sys_perf_event_open: pid 9926 cpu 0 group_fd -1 flags 0x8 = 4
...
Suggested-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/n/tip-dkvxxbeg7lu74155d4jhlmc9@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.