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Commit b93f7978 authored by Xiao Guangrong's avatar Xiao Guangrong Committed by Ingo Molnar
Browse files

perf_event: Allocate children's perf_event_ctxp at the right time 



In current code, children task will allocate memory for
'child->perf_event_ctxp' if the parent is counted, we can
do it only if the parent allowed children inherit it.

It can save memory and reduce overhead.

Signed-off-by: default avatarXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Reviewed-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <4B1F19A8.5040805@cn.fujitsu.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent aa5452d7

kernel/perf_event.c

+22 −15
Original line number Diff line number Diff line
@@ -5083,7 +5083,7 @@ again: 
 */

int perf_event_init_task(struct task_struct *child)

{

	struct perf_event_context *child_ctx, *parent_ctx;

	struct perf_event_context *child_ctx = NULL, *parent_ctx;

	struct perf_event_context *cloned_ctx;

	struct perf_event *event;

	struct task_struct *parent = current;
@@ -5098,20 +5098,6 @@ int perf_event_init_task(struct task_struct *child) 
	if (likely(!parent->perf_event_ctxp))

		return 0;



	/*

	 * This is executed from the parent task context, so inherit

	 * events that have been marked for cloning.

	 * First allocate and initialize a context for the child.

	 */



	child_ctx = kzalloc(sizeof(struct perf_event_context), GFP_KERNEL);

	if (!child_ctx)

		return -ENOMEM;



	__perf_event_init_context(child_ctx, child);

	child->perf_event_ctxp = child_ctx;

	get_task_struct(child);



	/*

	 * If the parent's context is a clone, pin it so it won't get

	 * swapped under us.
@@ -5142,6 +5128,26 @@ int perf_event_init_task(struct task_struct *child) 
			continue;

		}



		if (!child->perf_event_ctxp) {

			/*

			 * This is executed from the parent task context, so

			 * inherit events that have been marked for cloning.

			 * First allocate and initialize a context for the

			 * child.

			 */



			child_ctx = kzalloc(sizeof(struct perf_event_context),

					    GFP_KERNEL);

			if (!child_ctx) {

				ret = -ENOMEM;

				goto exit;

			}



			__perf_event_init_context(child_ctx, child);

			child->perf_event_ctxp = child_ctx;

			get_task_struct(child);

		}



		ret = inherit_group(event, parent, parent_ctx,

					     child, child_ctx);

		if (ret) {
@@ -5170,6 +5176,7 @@ int perf_event_init_task(struct task_struct *child) 
		get_ctx(child_ctx->parent_ctx);

	}



exit:

	mutex_unlock(&parent_ctx->mutex);



	perf_unpin_context(parent_ctx);