Optimus: cann't 'rmmod/modprobe -r' after ~1000 times of 'primus ls' runs.
=x11-drivers/nvidia-driver-340.32

[17231.601280] ------------[ cut here ]------------
[17231.601292] WARNING: CPU: 2 PID: 27492 at fs/proc/generic.c:315 proc_register+0xb8/0x130()
[17231.601294] proc_dir_entry 'driver/nvidia' already registered
[17231.601296] Modules linked in: nvidia(PO+) uvcvideo vhba(O) bbswitch(O) vboxnetadp(O) vboxnetflt(O) vboxdrv(O) squashfs aufs videobuf2_vmalloc videobuf2_memops videobuf2_core videodev i915 i2c
_algo_bit drm_kms_helper drm intel_agp i2c_core snd_hda_codec_hdmi intel_gtt snd_hda_codec_conexant snd_hda_codec_generic snd_hda_intel snd_hda_controller snd_hda_codec agpgart intel_ips snd_hwdep video asus_laptop input_poll
dev dm_snapshot dm_bufio dm_crypt dm_mirror dm_region_hash dm_log dm_mod [last unloaded: nvidia]
[17231.601330] CPU: 2 PID: 27492 Comm: modprobe Tainted: P        W  O  3.15.9-backbone #2
[17231.601332] Hardware name: ASUSTeK Computer Inc.         P52Jc/P52Jc, BIOS P52Jc.210 05/09/2011
[17231.601333]  0000000000000009 ffffffff81607325 ffff88021cdc3c78 ffffffff81099add
[17231.601336]  ffff880241e54d80 ffff88021cdc3cc8 ffff88023faa7480 ffff88024280a880
[17231.601339]  ffff880241e54d80 ffffffff81099b47 ffffffff8178ce10 0000000000000028
[17231.601342] Call Trace:
[17231.601350]  [<ffffffff81607325>] ? dump_stack+0x41/0x51
[17231.601356]  [<ffffffff81099add>] ? warn_slowpath_common+0x6d/0x90
[17231.601359]  [<ffffffff81099b47>] ? warn_slowpath_fmt+0x47/0x50
[17231.601362]  [<ffffffff811c7698>] ? proc_register+0xb8/0x130
[17231.601365]  [<ffffffff811c77f7>] ? proc_mkdir_data+0x47/0x70
[17231.601479]  [<ffffffffa1264499>] ? nv_register_procfs+0x39/0x1b0 [nvidia]
[17231.601543]  [<ffffffffa16f2285>] ? nvidia_init_module+0x285/0x786 [nvidia]
[17231.601604]  [<ffffffffa16f2795>] ? nv_drm_init+0xf/0xf [nvidia]
[17231.601665]  [<ffffffffa16f2816>] ? nvidia_frontend_init_module+0x81/0xb1 [nvidia]
[17231.601670]  [<ffffffff8100031a>] ? do_one_initcall+0xea/0x130
[17231.601675]  [<ffffffff810b875c>] ? __blocking_notifier_call_chain+0x4c/0x60
[17231.601678]  [<ffffffff81106fb6>] ? load_module+0x17e6/0x1fc0
[17231.601684]  [<ffffffff81104c60>] ? symbol_put_addr+0x30/0x30
[17231.601687]  [<ffffffff811078ad>] ? SyS_finit_module+0x6d/0x70
[17231.601691]  [<ffffffff8160df26>] ? system_call_fastpath+0x1a/0x1f
[17231.601693] ---[ end trace 251b0c17cafbeeb4 ]---
[17231.601760] vgaarb: device changed decodes: PCI:0000:01:00.0,olddecodes=none,decodes=none:owns=none
[17231.602516] [drm] Initialized nvidia-drm 0.0.0 20130102 for 0000:01:00.0 on minor 1
[17231.602526] NVRM: loading NVIDIA UNIX x86_64 Kernel Module  340.32  Tue Aug  5 20:58:26 PDT 2014
[17231.604924] nvidia 0000:01:00.0: irq 48 for MSI/MSI-X