Re: [PATCH] Silly bitmap size accounting fix

[Nick Piggin <nickpiggin@yahoo.com.au>]

Steven Rostedt wrote:
> > > +/*
> > > + * Calculate BITMAP_SIZE.
> > > + *  The bitmask holds MAX_PRIO bits + 1 for the delimiter.
> >
> > + * Calculation is to find the minimum number of longs that holds MAX_PRIO+1 bits:
> > + *  size-in-chars = ceiling((MAX_PRIO+1) / CHAR_BITS)
> > + *  size-in-longs = ceiling(size-in-chars / sizeof(long))
> >
> >
> > > + */
> > > #define BITMAP_SIZE ((((MAX_PRIO+1+7)/8)+sizeof(long)-1)/sizeof(long))
>
> What do you think of the following comment, better?

Cool, thanks.

> -- Steve
>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
>
> Index: linux-2.6.17-rc3-mm1/kernel/sched.c
> ===================================================================
> --- linux-2.6.17-rc3-mm1.orig/kernel/sched.c	2006-05-12 04:02:32.000000000 -0400
> +++ linux-2.6.17-rc3-mm1/kernel/sched.c	2006-05-13 10:50:44.000000000 -0400
> @@ -192,6 +192,13 @@ static inline unsigned int task_timeslic
>   * These are the runqueue data structures:
>   */
>
> +/*
> + * Calculate BITMAP_SIZE.
> + *  The bitmask holds MAX_PRIO bits + 1 for the delimiter.
> + *  BITMAP_SIZE is the minimum number of longs that holds MAX_PRIO+1 bits:
> + *   size-in-bytes = ceiling((MAX_PRIO+1) / BITS_PER_BYTE)
> + *   size-in-longs = ceiling(size-in-bytes / sizeof(long))
> + */
>  #define BITMAP_SIZE ((((MAX_PRIO+1+7)/8)+sizeof(long)-1)/sizeof(long))
>
>  typedef struct runqueue runqueue_t;


--
SUSE Labs, Novell Inc.
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