From: Xiao Guangrong Date: Wed, 9 Dec 2009 03:29:44 +0000 (+0800) Subject: perf_event: Allocate children's perf_event_ctxp at the right time X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=b93f7978ad6b46133e9453b90ccc057dc2429e75;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git 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 Reviewed-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Paul Mackerras LKML-Reference: <4B1F19A8.5040805@cn.fujitsu.com> Signed-off-by: Ingo Molnar --- diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 2b06c45bfba9..77641ae6b23f 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -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);