Re: [patch] CFS scheduler, -v8

Mike Galbraith
2007-05-02T06:37:23Z

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