On Tue, Jun 17, 2014 at 11:29:33AM +0400, Vladimir Davydov wrote:
> Hi,
>
> On Tue, Jun 17, 2014 at 10:09:52AM +0900, Joonsoo Kim wrote:
> [...]
> > To fix the problem, I introduces object status buffer on each slab.
> > With this, we can track object status precisely, so slab leak detector
> > would not access active object and no kernel oops would occur.
> > Memory overhead caused by this fix is only imposed to
> > CONFIG_DEBUG_SLAB_LEAK which is mainly used for debugging, so memory
> > overhead isn't big problem.
> [...]
> >
> > +static size_t calculate_freelist_size(int nr_objs, size_t align)
> > +{
> > + size_t freelist_size;
> > +
> > + freelist_size = nr_objs * sizeof(freelist_idx_t);
> > + if (IS_ENABLED(CONFIG_DEBUG_SLAB_LEAK))
> > + freelist_size += nr_objs * sizeof(char);
> > +
> > + if (align)
> > + freelist_size = ALIGN(freelist_size, align);
> > +
> > + return freelist_size;
> > +}
> > +
> > static int calculate_nr_objs(size_t slab_size, size_t buffer_size,
> > size_t idx_size, size_t align)
> > {
> > int nr_objs;
> > + size_t remained_size;
> > size_t freelist_size;
> > + int extra_space = 0;
> >
> > + if (IS_ENABLED(CONFIG_DEBUG_SLAB_LEAK))
> > + extra_space = sizeof(char);
> > /*
> > * Ignore padding for the initial guess. The padding
> > * is at most @align-1 bytes, and @buffer_size is at
> > @@ -590,14 +641,15 @@ static int calculate_nr_objs(size_t slab_size, size_t
> > buffer_size,
> > * into the memory allocation when taking the padding
> > * into account.
> > */
> > - nr_objs = slab_size / (buffer_size + idx_size);
> > + nr_objs = slab_size / (buffer_size + idx_size + extra_space);
>
> There is one more function that wants to know how much space per object
> is spent for management. It's calculate_slab_order():
>
> if (flags & CFLGS_OFF_SLAB) {
> /*
> * Max number of objs-per-slab for caches which
> * use off-slab slabs. Needed to avoid a possible
> * looping condition in cache_grow().
> */
> offslab_limit = size;
> offslab_limit /= sizeof(freelist_idx_t);
>
> if (num > offslab_limit)
> break;
> }
>
> May be, we should update it too?
Hello, Vladimir.
Yes, you are right! I sent v2 with this update. :)
Thanks.
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