Messages in this thread | | | Date | Thu, 2 Aug 2018 14:22:03 +0800 | From | zhong jiang <> | Subject | Re: [Question] A novel case happened when using mempool allocate memory. |
| |
On 2018/8/1 23:37, Matthew Wilcox wrote: > On Wed, Aug 01, 2018 at 11:31:15PM +0800, zhong jiang wrote: >> Hi, Everyone >> >> I ran across the following novel case similar to memory leak in linux-4.1 stable when allocating >> memory object by kmem_cache_alloc. it rarely can be reproduced. >> >> I create a specific mempool with 24k size based on the slab. it can not be merged with >> other kmem cache. I record the allocation and free usage by atomic_add/sub. After a while, >> I watch the specific slab consume most of total memory. After halting the code execution. >> The counter of allocation and free is equal. Therefore, I am sure that module have released >> all meory resource. but the statistic of specific slab is very high but stable by checking /proc/slabinfo. > Please post the code. > > . >
when module is loaded. we create the specific mempool. The code flow is as follows.
mem_pool_create() {
slab_cache = kmem_cache_create(name, item_size, 0, 0 , NULL);
mempoll_create(min_pool_size, mempool_alloc_slab, mempool_free_slab, slab_cache); //min_pool_size is assigned to 1024 atomic_set(pool->statistics, 0); }
we allocate memory from specific mempool , The code flow is as follows.
mem_alloc() { mempool_alloc(pool, gfp_flags);
atomic_inc(pool->statistics); }
we release memory to specific mempool . The code flow is as follows. mem_free() { mempool_free(object_ptr, pool);
atomic_dec(pool->statistics); }
when we unregister the module, the memory has been taken up will get back the system. the code flow is as follows.
mem_pool_destroy() { mempool_destroy(pool); kmem_cache_destroy(slab_cache); }
From the above information. I assume the specific kmem_cache will not take up overmuch memory when halting the execution and pool->statistics is equal to 0.
I have no idea about the issue.
Thanks zhong jiang
| |