Kernel memory leak. slab debug.
 

Hi,

I have a question about how to find a memory leak in the slab.

I am using a Windriver linux distribution and noticed that free memory was going down. After I enabled slub_debug, I noticed that the buf_acquire is allocating the memory and skb_release_data is freeing it (see below). The numbers (buf_acquire, skb_release_data) seem to match but the # of active objects keeps on increasing until there is no memory left. How can I proceed further as to why the slab is not being freed?

Thanks for your help.

from slabtop: 349594 281787 80% 4.07K 49942 7 1598144K kmalloc-4096

sort -n /sys/kernel/slab/kmalloc-4096/alloc_calls 259945 buf_acquire+0x30/0x70 [tipc] age=251/2199820/3285324 pid=3789 cpus=0-7

from /sys/kernel/slab/kmalloc-4096/free_calls 260208 skb_release_data +0x85/0xd0 age=1499/2291151/4037734 pid=4722-31618 cpus=0-7

When I notice strange kernel related problems, first thing I try is booting with another kernel version (preferably much older or much newer). This may not be the detailed answer you're looking for but I hope it helps.

One thing to remember is that Linux will use the entire "unused" memory for buffers. If nothing needs the space, it will just remain. If new processes (or I/O) needs memory it will flush these buffers and reuse the space.

The major identification of a kernel leak is when your system hangs...