Messages in this thread | | | Date | Tue, 17 Jun 2014 11:29:33 +0400 | From | Vladimir Davydov <> | Subject | Re: [PATCH] slab: fix oops when reading /proc/slab_allocators |
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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?
Thanks.
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