linux-kernel - Re: [PATCH] [4/4] SCHED: Use a lookup array in sd_level_to

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Message-ID: <20081112152828.GM3810@one.firstfloor.org>
Date:	Wed, 12 Nov 2008 16:28:28 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andi Kleen <andi@...stfloor.org>, mingo@...e.hu,
	linux-kernel@...r.kernel.org, peterz@...radead.org
Subject: Re: [PATCH] [4/4] SCHED: Use a lookup array in sd_level_to_string

On Wed, Nov 12, 2008 at 03:47:09PM +0100, Johannes Weiner wrote:
> > +#define T(x) [SD_LV_ ## x ] = #T
> 
> Shouldn't                         ^ that be x?

Yes good point. Thanks. Revised patch appended.

-Andi

---

SCHED: Use a lookup array in sd_level_to_string v2

Generates better/shorter code. Doesn't matter much because it's only
a SCHED_DEBUG function. 

v2: Fix stupid typo thanks to Johannes Weiner

Signed-off-by: Andi Kleen <ak@...ux.intel.com>

---
 kernel/sched.c |   29 +++++++++++------------------
 1 file changed, 11 insertions(+), 18 deletions(-)

Index: linux-2.6.28-rc4-test/kernel/sched.c
===================================================================
--- linux-2.6.28-rc4-test.orig/kernel/sched.c	2008-11-12 16:35:02.000000000 +0100
+++ linux-2.6.28-rc4-test/kernel/sched.c	2008-11-12 16:35:48.000000000 +0100
@@ -6629,24 +6629,17 @@
 
 static inline const char *sd_level_to_string(enum sched_domain_level lvl)
 {
-	switch (lvl) {
-	case SD_LV_NONE:
-			return "NONE";
-	case SD_LV_SIBLING:
-			return "SIBLING";
-	case SD_LV_MC:
-			return "MC";
-	case SD_LV_CPU:
-			return "CPU";
-	case SD_LV_NODE:
-			return "NODE";
-	case SD_LV_ALLNODES:
-			return "ALLNODES";
-	case SD_LV_MAX:
-			return "MAX";
-
-	}
-	return "MAX";
+	static const char *lva[] = {
+#define T(x) [SD_LV_ ## x ] = #x
+		T(NONE),
+		T(SIBLING),
+		T(MC),
+		T(CPU),
+		T(NODE),
+		T(ALLNODES),
+#undef T
+	};
+	return (unsigned)lvl < ARRAY_SIZE(lva) ? lva[lvl] : "MAX";
 }
 
 static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
--
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