（这是从 ubuntu 官方论坛发来的。那里没人回答，希望我在这里能更幸运一些）
自从我在新笔记本电脑上安装了 xubuntu 14.04.2 LTS 后，出现了这种奇怪的行为，您可以在这些屏幕中看到（插入黑条是为了删除私人数据，否则这些屏幕代表我在桌面上实际看到的内容）：
当我登录时，没有采取任何特殊操作，就会发生这种情况，当我使用浏览器或同时打开多个窗口时，问题会变得更加严重。
这是我的笔记本电脑的规格：
- 宏碁 Aspire V15（代码 V3-572G-75CA）
- 英特尔酷睿 i7 5500U 2.4GHz
- Nvidia GeForce 840M 2GB 显存
- 8GB DDR3
- 1000 GB 硬盘
以下是我从 lspci 获得的信息：
00:00.0 Host bridge: Intel Corporation Broadwell-U Host Bridge -OPI (rev 09)
00:02.0 VGA compatible controller: Intel Corporation Broadwell-U Integrated Graphics (rev 09)
00:03.0 Audio device: Intel Corporation Broadwell-U Audio Controller (rev 09)
00:14.0 USB controller: Intel Corporation Wildcat Point-LP USB xHCI Controller (rev 03)
00:16.0 Communication controller: Intel Corporation Wildcat Point-LP MEI Controller #1 (rev 03)
00:1b.0 Audio device: Intel Corporation Wildcat Point-LP High Definition Audio Controller (rev 03)
00:1c.0 PCI bridge: Intel Corporation Wildcat Point-LP PCI Express Root Port #1 (rev e3)
00:1c.2 PCI bridge: Intel Corporation Wildcat Point-LP PCI Express Root Port #3 (rev e3)
00:1c.3 PCI bridge: Intel Corporation Wildcat Point-LP PCI Express Root Port #4 (rev e3)
00:1c.4 PCI bridge: Intel Corporation Wildcat Point-LP PCI Express Root Port #5 (rev e3)
00:1f.0 ISA bridge: Intel Corporation Wildcat Point-LP LPC Controller (rev 03)
00:1f.2 SATA controller: Intel Corporation Wildcat Point-LP SATA Controller [AHCI Mode] (rev 03)
00:1f.3 SMBus: Intel Corporation Wildcat Point-LP SMBus Controller (rev 03)
00:1f.6 Signal processing controller: Intel Corporation Wildcat Point-LP Thermal Management Controller (rev 03)
02:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. Device 5287 (rev 01)
02:00.1 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 12)
03:00.0 Network controller: Intel Corporation Wireless 7260 (rev bb)
04:00.0 3D controller: NVIDIA Corporation GM108M [GeForce 840M] (rev a2)
以下是图形设备的 -v -s 详细信息：
00:02.0 VGA compatible controller: Intel Corporation Broadwell-U Integrated Graphics (rev 09) (prog-if 00 [VGA controller])
Subsystem: Acer Incorporated [ALI] Device 0940
Flags: bus master, fast devsel, latency 0, IRQ 69
Memory at c2000000 (64-bit, non-prefetchable) [size=16M]
Memory at d0000000 (64-bit, prefetchable) [size=256M]
I/O ports at 5000 [size=64]
Expansion ROM at <unassigned> [disabled]
Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
Capabilities: [d0] Power Management version 2
Capabilities: [a4] PCI Advanced Features
Kernel driver in use: i915
04:00.0 3D controller: NVIDIA Corporation GM108M [GeForce 840M] (rev a2)
Subsystem: Acer Incorporated [ALI] Device 0942
Flags: fast devsel, IRQ 16
Memory at c3000000 (32-bit, non-prefetchable) [size=16M]
Memory at b0000000 (64-bit, prefetchable) [size=256M]
Memory at c0000000 (64-bit, prefetchable) [size=32M]
I/O ports at 3000 [size=128]
Expansion ROM at <ignored> [disabled]
Capabilities: [60] Power Management version 3
Capabilities: [68] MSI: Enable- Count=1/1 Maskable- 64bit+
Capabilities: [78] Express Endpoint, MSI 00
Capabilities: [100] Virtual Channel
Capabilities: [250] Latency Tolerance Reporting
Capabilities: [258] L1 PM Substates
Capabilities: [128] Power Budgeting <?>
Capabilities: [600] Vendor Specific Information: ID=0001 Rev=1 Len=024 <?>
Capabilities: [900] #19
我还在 dmsg 中收到了这些值得报告的奇怪消息：
[ 11.359540] fbcon: inteldrmfb (fb0) is primary device
[ 11.359591] Console: switching to colour frame buffer device 170x48
[ 11.359607] i915 0000:00:02.0: fb0: inteldrmfb frame buffer device
[ 11.359608] i915 0000:00:02.0: registered panic notifier
[ 11.383686] ACPI: Video Device [GFX0] (multi-head: yes rom: no post: no)
[ 11.383759] input: Video Bus as /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:00/input/input12
[ 11.383891] [Firmware Bug]: ACPI(PXSX) defines _DOD but not _DOS
[ 11.383898] ACPI: Video Device [PXSX] (multi-head: yes rom: yes post: no)
[ 11.383929] input: Video Bus as /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:52/LNXVIDEO:01/input/input13
[ 11.383991] [drm] Initialized i915 1.6.0 20080730 for 0000:00:02.0 on minor 0
[ 11.384356] snd_hda_intel 0000:00:03.0: irq 70 for MSI/MSI-X
[ 11.393858] input: HDA Intel HDMI HDMI/DP,pcm=3 as /devices/pci0000:00/0000:00:03.0/sound/card0/input14
[ 11.393923] input: HDA Intel HDMI HDMI/DP,pcm=7 as /devices/pci0000:00/0000:00:03.0/sound/card0/input15
[ 11.393980] input: HDA Intel HDMI HDMI/DP,pcm=8 as /devices/pci0000:00/0000:00:03.0/sound/card0/input16
[ 11.116752] VGA switcheroo: detected Optimus DSM method \_SB_.PCI0.RP05.PXSX handle
[ 11.116774] checking generic (d0000000 410000) vs hw (b0000000 10000000)
[ 11.116776] checking generic (d0000000 410000) vs hw (c0000000 2000000)
[ 11.116805] nouveau 0000:04:00.0: enabling device (0106 -> 0107)
[ 11.117047] nouveau ![ DEVICE][0000:04:00.0] unknown Maxwell chipset
[ 11.117051] nouveau E[ DEVICE][0000:04:00.0] unknown chipset, 0x118010a2
[ 11.117053] nouveau E[ DRM] failed to create 0x80000080, -22
[ 11.117273] nouveau: probe of 0000:04:00.0 failed with error -22
[ 11.117658] iwlwifi 0000:03:00.0: Unsupported splx structure
[ 11.118163] input: Acer BMA150 accelerometer as /devices/virtual/input/input8
[ 11.125464] [drm] Memory usable by graphics device = 4096M
[ 11.125468] checking generic (d0000000 410000) vs hw (d0000000 10000000)
[ 11.125469] fb: switching to inteldrmfb from EFI VGA
[ 11.125482] Console: switching to colour dummy device 80x25
[ 11.125545] [drm] Replacing VGA console driver
[ 11.126214] [drm] ACPI BIOS requests an excessive sleep of 10000 ms, using 1500 ms instead
[ 11.146760] i915 0000:00:02.0: irq 69 for MSI/MSI-X
[ 11.146771] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[ 11.146773] [drm] Driver supports precise vblank timestamp query.
[ 11.146802] vgaarb: device changed decodes: PCI:0000:00:02.0,olddecodes=io+mem,decodes=io+mem:owns=io+mem
[ 11.187004] [drm] VBT doesn't support DRRS