Question about memory

(1) What's the necessary of qat_config_mem.ko ? I simply `rmmod` it while Nginx was still running and found Nginx worked and reloaded correctly.
(2) Next few days after I did (1), I found Nginx did't work, `dmesg` shows:
```
[1564771.408920] Nginx: page allocation failure: order:9, mode:0x3040d0
[1564771.416519] CPU: 29 PID: 13537 Comm: Nginx Tainted: G OE ------------ 3.10.0-327.el7.x86_64 #1
[1564771.428579] Hardware name: Huawei Technologies Co., Ltd. Tecal RH2288H V2-12L/BC11SRSG1, BIOS RMIBV503 03/09/2015
[1564771.439347] Call Trace:
[1564771.442148] [] dump_stack+0x19/0x1b
[1564771.447628] [] warn_alloc_failed+0x110/0x180
[1564771.453892] [] ? __alloc_pages_direct_compact+0x186/0x1b5
[1564771.461452] [] __alloc_pages_slowpath+0x5ef/0x826
[1564771.468152] [] __alloc_pages_nodemask+0x41a/0x440
[1564771.474841] [] kmalloc_large_node+0x60/0x8d
[1564771.481017] [] __kmalloc_node+0x222/0x280
[1564771.487006] [] ? filemap_fault+0x225/0x430
[1564771.493290] [] dev_mem_alloc.isra.6+0x12c/0x5f0 [usdm_drv]
[1564771.501108] [] mem_ioctl+0x167/0x200 [usdm_drv]
[1564771.507752] [] do_vfs_ioctl+0x2e5/0x4c0
[1564771.513670] [] SyS_ioctl+0xa1/0xc0
[1564771.519113] [] system_call_fastpath+0x16/0x1b
[1564771.525535] Mem-Info:

[1564772.301905] usdm_drv: userMemAlloc:380 Unable to allocate memory slab or wrong alignment: (null)
[1564772.312064] usdm_drv: dev_mem_alloc:566 userMemAlloc failed

```
Seemed memory leaked but the memory usage of Nginx was low(I event restarted the Nginx but it didn't work still).
Then I found that `Cached` in `/proc/meminfo` is very large. Yes, I do a lot of log action, and I think the system would reclaim it.
(3) I removed the log file, then the `Cached` in `/proc/meminfo` recovered, and restarted Nginx, it works now!
(4) Does it related to`rmmod qat_config_mem`