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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: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Reviewed-by: Frederic 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: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Xiao Guangrong 2009-12-09 11:29:44 +08:00 committed by Ingo Molnar
parent aa5452d70c
commit b93f7978ad
1 changed files with 22 additions and 15 deletions
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37
kernel/perf_event.c
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@ -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);