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perf/core: Fix installing cgroup events on CPU

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There's two problems when installing cgroup events on CPUs: firstly
list_update_cgroup_event() only tries to set cpuctx->cgrp for the
first event, if that mismatches on @cgrp we'll not try again for later
additions.

Secondly, when we install a cgroup event into an active context, only
issue an event reprogram when the event matches the current cgroup
context. This avoids a pointless event reprogramming.

Signed-off-by: leilei.lin <leilei.lin@alibaba-inc.com>
[ Improved the changelog and comments. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: brendan.d.gregg@gmail.com
Cc: eranian@gmail.com
Cc: linux-kernel@vger.kernel.org
Cc: yang_oliver@hotmail.com
Link: http://lkml.kernel.org/r/20180306093637.28247-1-linxiulei@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
leilei.lin 2018-03-06 17:36:37 +08:00 committed by Ingo Molnar
parent 8d5bce0c37
commit 33801b9474
1 changed files with 35 additions and 11 deletions
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46
kernel/events/core.c
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@ -937,27 +937,39 @@ list_update_cgroup_event(struct perf_event *event,
if (!is_cgroup_event(event))
return;
if (add && ctx->nr_cgroups++)
return;
else if (!add && --ctx->nr_cgroups)
return;
/*
* Because cgroup events are always per-cpu events,
* this will always be called from the right CPU.
*/
cpuctx = __get_cpu_context(ctx);
cpuctx_entry = &cpuctx->cgrp_cpuctx_entry;
/* cpuctx->cgrp is NULL unless a cgroup event is active in this CPU .*/
if (add) {
/*
* Since setting cpuctx->cgrp is conditional on the current @cgrp
* matching the event's cgroup, we must do this for every new event,
* because if the first would mismatch, the second would not try again
* and we would leave cpuctx->cgrp unset.
*/
if (add && !cpuctx->cgrp) {
struct perf_cgroup *cgrp = perf_cgroup_from_task(current, ctx);
list_add(cpuctx_entry, this_cpu_ptr(&cgrp_cpuctx_list));
if (cgroup_is_descendant(cgrp->css.cgroup, event->cgrp->css.cgroup))
cpuctx->cgrp = cgrp;
} else {
list_del(cpuctx_entry);
cpuctx->cgrp = NULL;
}
if (add && ctx->nr_cgroups++)
return;
else if (!add && --ctx->nr_cgroups)
return;
/* no cgroup running */
if (!add)
cpuctx->cgrp = NULL;
cpuctx_entry = &cpuctx->cgrp_cpuctx_entry;
if (add)
list_add(cpuctx_entry, this_cpu_ptr(&cgrp_cpuctx_list));
else
list_del(cpuctx_entry);
}
#else /* !CONFIG_CGROUP_PERF */
@ -2489,6 +2501,18 @@ static int __perf_install_in_context(void *info)
raw_spin_lock(&task_ctx->lock);
}
#ifdef CONFIG_CGROUP_PERF
if (is_cgroup_event(event)) {
/*
* If the current cgroup doesn't match the event's
* cgroup, we should not try to schedule it.
*/
struct perf_cgroup *cgrp = perf_cgroup_from_task(current, ctx);
reprogram = cgroup_is_descendant(cgrp->css.cgroup,
event->cgrp->css.cgroup);
}
#endif
if (reprogram) {
ctx_sched_out(ctx, cpuctx, EVENT_TIME);
add_event_to_ctx(event, ctx);