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
