[RFC 0/8] perf/x86: Add update attribute groups

From: Jiri Olsa
Date: Sat May 04 2019 - 08:53:03 EST

following up on [1], this patchset adds update attribute groups
to pmu and gets rid of the 'creative' attribute handling code.

In x86 pmu we mainly add attributes into following directories:
events, format, caps

so it seems like we could have just 3 attribute groups, but most of
the attributes presence depends on HW, which ends up with attributes
merging and all that 'creative' code we have now.

Currently, we have 'struct pmu::attr_groups', which is in its final
shape (merged) and it's added via sysfs_create_groups call when
registering the pmu:


This interface does not provide a way to have multiple attribute
groups, which could add files into same directory, all has to be
prepared ahead.

This patchset adds 'update attribute group', which is added via new
sysfs_update_groups function, after the initial set of attributes
is created. The group's is_visible function will cover its HW

This will allow us to update "events" or "format" directories with
attributes that depend on various HW config.

For example having group_format_extra group, that updates "format"
directory, only if pmu version is 2 and higher:

static umode_t
lbr_is_visible(struct kobject *kobj, struct attribute *attr, int i)
return x86_pmu.lbr_nr ? attr->mode : 0;

static struct attribute_group group_caps_lbr = {
.name = "caps",
.attrs = lbr_attrs,
.is_visible = lbr_is_visible,

Note that some of the groups are defined without 'attrs' set,
which is assigned later based on the detected cpu model.

And finally we'll end up with just a single set of attribute groups:

static const struct attribute_group *attr_update[] = {

that is passed to struct pmu.

Also available in:

thoughts? thanks,

[1] https://lore.kernel.org/lkml/20190318182116.17388-1-jolsa@xxxxxxxxxx/
Jiri Olsa (8):
sysfs: Add sysfs_update_groups function
perf: Add attr_groups_update into struct pmu
perf/x86: Get rid of x86_pmu::event_attrs
perf/x86: Use the new pmu::update_attrs attribute group
perf/x86: Add is_visible attribute_group callback for base events
perf/x86: Use update attribute groups for caps
perf/x86/intel: Use update attributes for skylake format
perf/x86: Use update attribute groups for default attributes

arch/x86/events/core.c | 105 +++++++++++++++------------------------------------------------------------------------------------------
arch/x86/events/intel/core.c | 144 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----------------------------------------------------
arch/x86/events/perf_event.h | 7 +------
fs/sysfs/group.c | 43 ++++++++++++++++++++++++++++---------------
include/linux/perf_event.h | 1 +
include/linux/sysfs.h | 2 ++
kernel/events/core.c | 6 ++++++
7 files changed, 145 insertions(+), 163 deletions(-)