On Thu, May 05, 2011 at 07:43:58AM +0200, Otto Moerbeek wrote:
> On Wed, May 04, 2011 at 11:56:58PM -0500, Amit Kulkarni wrote:
>
> > > The random number is derived from a global, which is incremented by a
> > > few bits every time a chunk is needed (with a small optimization if
> > > only one free slot is left).
> > >
> >
> > I have no feedback on this diff but a question on random placing in
> > another two functions.
> >
> > In static void unmap()
> > for (i = 0; tounmap > 0 && i < mopts.malloc_cache; i++) {
> > r = &d->free_regions[(i + offset) & (mopts.malloc_cache -
> > 1)];
> >
> > In static void map()
> > for (i = 0; i < mopts.malloc_cache; i++) {
> > r = &d->free_regions[(i + offset) & (mopts.malloc_cache -
> > 1)];
> >
> > AFAIK
> > malloc_cache = 64
> > offset = {0 , 15} interval
> > free_regions[MALLOC_MAXCACHE] = 256
> >
> > the effect of logical 'and' is useless because you are only
> > really indexing free_regions from i+15, max of 64+15.
> >
> > If you want to index free_regions randomly over its full range, maybe you
> > should do something else?
>
> malloc_cache is a power of the, so a bitwise and with malloc_cache - 1
> is equivalent to modulo malloc_cache.
of two, that is.
Room is reserved for MALLOC_MAXCACHE pointers, but only malloc_cache
are ever used. So doing a modulo malloc_cache is ok.
-Otto
