Question about memory

[mrpre]

(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]  [<ffffffff81650e6a>] dump_stack+0x19/0x1b
[1564771.447628]  [<ffffffff81179ac0>] warn_alloc_failed+0x110/0x180
[1564771.453892]  [<ffffffff8164b57d>] ? __alloc_pages_direct_compact+0x186/0x1b5
[1564771.461452]  [<ffffffff8164bb9b>] __alloc_pages_slowpath+0x5ef/0x826
[1564771.468152]  [<ffffffff8117dcba>] __alloc_pages_nodemask+0x41a/0x440
[1564771.474841]  [<ffffffff8164d062>] kmalloc_large_node+0x60/0x8d
[1564771.481017]  [<ffffffff811d1c32>] __kmalloc_node+0x222/0x280
[1564771.487006]  [<ffffffff81176265>] ? filemap_fault+0x225/0x430
[1564771.493290]  [<ffffffffa0502dfc>] dev_mem_alloc.isra.6+0x12c/0x5f0 [usdm_drv]
[1564771.501108]  [<ffffffffa0503427>] mem_ioctl+0x167/0x200 [usdm_drv]
[1564771.507752]  [<ffffffff81204575>] do_vfs_ioctl+0x2e5/0x4c0
[1564771.513670]  [<ffffffff812047f1>] SyS_ioctl+0xa1/0xc0
[1564771.519113]  [<ffffffff816630fd>] 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 tormmod qat_config_mem