linux-kernel - [PATCH] clk: make clk_core_lookup faster by using clk name hash

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Date:   Tue, 5 Oct 2021 14:59:49 +0800
From:   Mark-PK Tsai <mark-pk.tsai@...iatek.com>
To:     <mturquette@...libre.com>, <sboyd@...nel.org>
CC:     <mark-pk.tsai@...iatek.com>, <yj.chiang@...iatek.com>,
        <matthias.bgg@...il.com>, <linux-clk@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>
Subject: [PATCH] clk: make clk_core_lookup faster by using clk name hash

Compare hash value before strcmp the full name to make
clk_core_lookup faster.

It make clk driver probe 30 percent faster on the platform
have 1483 registered clks and average clock name length 20.

Signed-off-by: Mark-PK Tsai <mark-pk.tsai@...iatek.com>
---
 drivers/clk/clk.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 65508eb89ec9..d5f65fda3db8 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -89,6 +89,7 @@ struct clk_core {
 	struct hlist_node	debug_node;
 #endif
 	struct kref		ref;
+	unsigned int		hash;
 };
 
 #define CREATE_TRACE_POINTS
@@ -292,16 +293,17 @@ struct clk_hw *clk_hw_get_parent(const struct clk_hw *hw)
 EXPORT_SYMBOL_GPL(clk_hw_get_parent);
 
 static struct clk_core *__clk_lookup_subtree(const char *name,
+					     unsigned int hash,
 					     struct clk_core *core)
 {
 	struct clk_core *child;
 	struct clk_core *ret;
 
-	if (!strcmp(core->name, name))
+	if (hash == core->hash && !strcmp(core->name, name))
 		return core;
 
 	hlist_for_each_entry(child, &core->children, child_node) {
-		ret = __clk_lookup_subtree(name, child);
+		ret = __clk_lookup_subtree(name, hash, child);
 		if (ret)
 			return ret;
 	}
@@ -313,20 +315,22 @@ static struct clk_core *clk_core_lookup(const char *name)
 {
 	struct clk_core *root_clk;
 	struct clk_core *ret;
+	unsigned int hash;
 
 	if (!name)
 		return NULL;
 
+	hash = full_name_hash(NULL, name, strlen(name));
 	/* search the 'proper' clk tree first */
 	hlist_for_each_entry(root_clk, &clk_root_list, child_node) {
-		ret = __clk_lookup_subtree(name, root_clk);
+		ret = __clk_lookup_subtree(name, hash, root_clk);
 		if (ret)
 			return ret;
 	}
 
 	/* if not found, then search the orphan tree */
 	hlist_for_each_entry(root_clk, &clk_orphan_list, child_node) {
-		ret = __clk_lookup_subtree(name, root_clk);
+		ret = __clk_lookup_subtree(name, hash, root_clk);
 		if (ret)
 			return ret;
 	}
@@ -3827,6 +3831,7 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
 		goto fail_name;
 	}
 
+	core->hash = full_name_hash(NULL, core->name, strlen(core->name));
 	if (WARN_ON(!init->ops)) {
 		ret = -EINVAL;
 		goto fail_ops;
-- 
2.18.0