Subject: [PATCH 05/11] ftrace: create memcache for hash entries

From: Changbin Du <[email-masked]>
Date: Sun, 25 Aug 2019 21:23:24 +0800

When CONFIG_FTRACE_FUNC_PROTOTYPE is enabled, thousands of
ftrace_func_entry instances are created. So create a dedicated
memcache to enhance performance.

Signed-off-by: Changbin Du <[email-masked]>
---
 kernel/trace/ftrace.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index a314f0768b2c..cfcb8dad93ea 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -94,6 +94,8 @@ struct ftrace_ops *function_trace_op __read_mostly = &ftrace_list_end;
 /* What to set function_trace_op to */
 static struct ftrace_ops *set_function_trace_op;
 
+struct kmem_cache *hash_entry_cache;
+
 static bool ftrace_pids_enabled(struct ftrace_ops *ops)
 {
 	struct trace_array *tr;
@@ -1169,7 +1171,7 @@ static int add_hash_entry(struct ftrace_hash *hash, unsigned long ip,
 {
 	struct ftrace_func_entry *entry;
 
-	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
+	entry = kmem_cache_alloc(hash_entry_cache, GFP_KERNEL);
 	if (!entry)
 		return -ENOMEM;
 
@@ -6153,6 +6155,15 @@ void __init ftrace_init(void)
 	if (ret)
 		goto failed;
 
+	hash_entry_cache = kmem_cache_create("ftrace-hash",
+					     sizeof(struct ftrace_func_entry),
+					     sizeof(struct ftrace_func_entry),
+					     0, NULL);
+	if (!hash_entry_cache) {
+		pr_err("failed to create ftrace hash entry cache\n");
+		goto failed;
+	}
+
 	count = __stop_mcount_loc - __start_mcount_loc;
 	if (!count) {
 		pr_info("ftrace: No functions to be traced?\n");
@@ -6172,6 +6183,10 @@ void __init ftrace_init(void)
 
 	return;
  failed:
+	if (hash_entry_cache) {
+		kmem_cache_destroy(hash_entry_cache);
+		hash_entry_cache = NULL;
+	}
 	ftrace_disabled = 1;
 }
 
-- 
2.20.1

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