nouveau cause unexpected delays and periodic freeze (<0.2s) when rendering complicated 3D scene. Here dmesg during lags (repeat many times): [46444.498018] nouveau E[ PGRAPH][0000:01:00.0] TRAP_VFETCH FAULT [46444.498028] nouveau E[ PGRAPH][0000:01:00.0] TRAP_VFETCH 00f00000 0000fe0c 00000000 00000000 [46444.498031] nouveau E[ PGRAPH][0000:01:00.0] TRAP [46444.498037] nouveau E[ PGRAPH][0000:01:00.0] ch 4 [0x001f8eb000 el.x86.linux.bi[7941]] subc 5 class 0x8297 mthd 0x0f04 data 0x3f800000 [46444.498045] nouveau E[ PFB][0000:01:00.0] trapped read at 0x0000000000 on channel 0x0001f8eb [el.x86.linux.bi[7941]] PGRAPH/VFETCH/00 reason: PT_NOT_PRESENT [46444.498070] nouveau E[ PGRAPH][0000:01:00.0] TRAP_VFETCH FAULT [46444.498082] nouveau E[ PGRAPH][0000:01:00.0] TRAP_VFETCH 00f00000 0000fe0c 00000000 00000000 [46444.498085] nouveau E[ PGRAPH][0000:01:00.0] TRAP [46444.498092] nouveau E[ PGRAPH][0000:01:00.0] ch 4 [0x001f8eb000 el.x86.linux.bi[7941]] subc 5 class 0x8297 mthd 0x0f04 data 0x40028f58 [46448.541527] nouveau E[ PGRAPH][0000:01:00.0] TRAP_VFETCH FAULT [46448.541537] nouveau E[ PGRAPH][0000:01:00.0] TRAP_VFETCH 00f00000 0000fe0c 00000000 00000000 [46448.541540] nouveau E[ PGRAPH][0000:01:00.0] TRAP [46448.541545] nouveau E[ PGRAPH][0000:01:00.0] ch 4 [0x001f8eb000 el.x86.linux.bi[7941]] subc 5 class 0x8297 mthd 0x0f04 data 0x3f800000 [46448.541557] nouveau E[ PFB][0000:01:00.0] trapped read at 0x0000000000 on channel 0x0001f8eb [el.x86.linux.bi[7941]] PGRAPH/VFETCH/00 reason: PT_NOT_PRESENT [46448.541590] nouveau E[ PGRAPH][0000:01:00.0] TRAP_VFETCH FAULT [46448.541601] nouveau E[ PGRAPH][0000:01:00.0] TRAP_VFETCH 00f00000 0000fe0c 00000000 00000000 [46448.541605] nouveau E[ PGRAPH][0000:01:00.0] TRAP [46448.541612] nouveau E[ PGRAPH][0000:01:00.0] ch 4 [0x001f8eb000 el.x86.linux.bi[7941]] subc 5 class 0x8297 mthd 0x0f04 data 0x00000000 But that problem is same with many 3D applications. Was seen at least from 3.2 to 3.9-rc7.