Revision 7f453c24b95a085fc7bd35d53b33abc4dc5a048b authored by Peter Zijlstra on 21 July 2009, 11:19:40 UTC, committed by Peter Zijlstra on 22 July 2009, 16:05:56 UTC
Anton noted that for inherited counters the counter-id as provided by PERF_SAMPLE_ID isn't mappable to the id found through PERF_RECORD_ID because each inherited counter gets its own id. His suggestion was to always return the parent counter id, since that is the primary counter id as exposed. However, these inherited counters have a unique identifier so that events like PERF_EVENT_PERIOD and PERF_EVENT_THROTTLE can be specific about which counter gets modified, which is important when trying to normalize the sample streams. This patch removes PERF_EVENT_PERIOD in favour of PERF_SAMPLE_PERIOD, which is more useful anyway, since changing periods became a lot more common than initially thought -- rendering PERF_EVENT_PERIOD the less useful solution (also, PERF_SAMPLE_PERIOD reports the more accurate value, since it reports the value used to trigger the overflow, whereas PERF_EVENT_PERIOD simply reports the requested period changed, which might only take effect on the next cycle). This still leaves us PERF_EVENT_THROTTLE to consider, but since that _should_ be a rare occurrence, and linking it to a primary id is the most useful bit to diagnose the problem, we introduce a PERF_SAMPLE_STREAM_ID, for those few cases where the full reconstruction is important. [Does change the ABI a little, but I see no other way out] Suggested-by: Anton Blanchard <anton@samba.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1248095846.15751.8781.camel@twins>
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cgroup_debug.c
/*
* kernel/cgroup_debug.c - Example cgroup subsystem that
* exposes debug info
*
* Copyright (C) Google Inc, 2007
*
* Developed by Paul Menage (menage@google.com)
*
*/
#include <linux/cgroup.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/rcupdate.h>
#include <asm/atomic.h>
static struct cgroup_subsys_state *debug_create(struct cgroup_subsys *ss,
struct cgroup *cont)
{
struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
if (!css)
return ERR_PTR(-ENOMEM);
return css;
}
static void debug_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
{
kfree(cont->subsys[debug_subsys_id]);
}
static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
{
return atomic_read(&cont->count);
}
static u64 taskcount_read(struct cgroup *cont, struct cftype *cft)
{
u64 count;
count = cgroup_task_count(cont);
return count;
}
static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
{
return (u64)(long)current->cgroups;
}
static u64 current_css_set_refcount_read(struct cgroup *cont,
struct cftype *cft)
{
u64 count;
rcu_read_lock();
count = atomic_read(¤t->cgroups->refcount);
rcu_read_unlock();
return count;
}
static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
{
return test_bit(CGRP_RELEASABLE, &cgrp->flags);
}
static struct cftype files[] = {
{
.name = "cgroup_refcount",
.read_u64 = cgroup_refcount_read,
},
{
.name = "taskcount",
.read_u64 = taskcount_read,
},
{
.name = "current_css_set",
.read_u64 = current_css_set_read,
},
{
.name = "current_css_set_refcount",
.read_u64 = current_css_set_refcount_read,
},
{
.name = "releasable",
.read_u64 = releasable_read,
},
};
static int debug_populate(struct cgroup_subsys *ss, struct cgroup *cont)
{
return cgroup_add_files(cont, ss, files, ARRAY_SIZE(files));
}
struct cgroup_subsys debug_subsys = {
.name = "debug",
.create = debug_create,
.destroy = debug_destroy,
.populate = debug_populate,
.subsys_id = debug_subsys_id,
};
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