linux-kernel - Re: [patch] CFS scheduler, -v8

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Date:	Wed, 02 May 2007 08:37:14 +0200
From:	Mike Galbraith <efault@....de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Con Kolivas <kernel@...ivas.org>,
	Nick Piggin <npiggin@...e.de>,
	Arjan van de Ven <arjan@...radead.org>,
	Peter Williams <pwil3058@...pond.net.au>,
	Thomas Gleixner <tglx@...utronix.de>, caglar@...dus.org.tr,
	Willy Tarreau <w@....eu>,
	Gene Heskett <gene.heskett@...il.com>, Mark Lord <lkml@....ca>,
	Zach Carter <linux@...hcarter.com>,
	buddabrod <buddabrod@...il.com>, Balbir Singh <balbir@...ibm.com>
Subject: Re: [patch] CFS scheduler, -v8

On Tue, 2007-05-01 at 23:22 +0200, Ingo Molnar wrote:
> i'm pleased to announce release -v8 of the CFS scheduler patchset. (The 
> main goal of CFS is to implement "desktop scheduling" with as high 
> quality as technically possible.)
...

> As usual, any sort of feedback, bugreport, fix and suggestion is more 
> than welcome,

Greetings,

I noticed a (harmless) bounds warning triggered by the reduction in size
of array->bitmap.  Patchlet below.

	-Mike

  CC      kernel/sched.o
kernel/sched_rt.c: In function ‘load_balance_start_rt’:
include/asm-generic/bitops/sched.h:30: warning: array subscript is above array bounds
kernel/sched_rt.c: In function ‘pick_next_task_rt’:
include/asm-generic/bitops/sched.h:30: warning: array subscript is above array bounds

--- linux-2.6.21-cfs.v8/include/asm-generic/bitops/sched.h.org	2007-05-02 07:16:47.000000000 +0200
+++ linux-2.6.21-cfs.v8/include/asm-generic/bitops/sched.h	2007-05-02 07:20:45.000000000 +0200
@@ -6,28 +6,23 @@
 
 /*
  * Every architecture must define this function. It's the fastest
- * way of searching a 140-bit bitmap where the first 100 bits are
- * unlikely to be set. It's guaranteed that at least one of the 140
- * bits is cleared.
+ * way of searching a 100-bit bitmap.  It's guaranteed that at least
+ * one of the 100 bits is cleared.
  */
 static inline int sched_find_first_bit(const unsigned long *b)
 {
 #if BITS_PER_LONG == 64
-	if (unlikely(b[0]))
+	if (b[0])
 		return __ffs(b[0]);
-	if (likely(b[1]))
-		return __ffs(b[1]) + 64;
-	return __ffs(b[2]) + 128;
+	return __ffs(b[1]) + 64;
 #elif BITS_PER_LONG == 32
-	if (unlikely(b[0]))
+	if (b[0])
 		return __ffs(b[0]);
-	if (unlikely(b[1]))
+	if (b[1])
 		return __ffs(b[1]) + 32;
-	if (unlikely(b[2]))
+	if (b[2])
 		return __ffs(b[2]) + 64;
-	if (b[3])
-		return __ffs(b[3]) + 96;
-	return __ffs(b[4]) + 128;
+	return __ffs(b[3]) + 96;
 #else
 #error BITS_PER_LONG not defined
 #endif


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