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228cf79376
v3: detection code is x86 and KVM specific, hide it under ifdef v2: add detection for virtual environments (KVM and Parallels) This patch is intended to improve performance in virtualized environments like Parallels Desktop or KVM/VirtualBox/QEMU (virtual ICH/AC97 audio). I/O access is very time-expensive operation in virtual world: VCPU can be rescheduled and in the worst case we get more than 10ms delay on each I/O access. In the virtual environment loop exit rule (old_civ == current_civ && old_picb == current_picb) is never satisfied, because old_picb is never the same as current_picb due to delay inspired by reading current_civ. As a result loop ended by timeout and we get 10x more I/O operations. Experimental data from Prallels Desktop 7, RHEL6 guest (I/O ops per second): Original code: In Port Counter Callback f014 41550 fffff00000179d00 ac97_bm_read_civ+0x000 f018 41387 fffff0000017a580 ac97_bm_read_picb+0x000 With patch: In Port Counter Callback f014 4090 fffff00000179d00 ac97_bm_read_civ+0x000 f018 1964 fffff0000017a580 ac97_bm_read_picb+0x000 Signed-off-by: Konstantin Ozerkov <kozerkov@parallels.com> Signed-off-by: Denis V. Lunev <den@openvz.org> Signed-off-by: Takashi Iwai <tiwai@suse.de> |
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| .. | ||
| aoa | ||
| arm | ||
| atmel | ||
| core | ||
| drivers | ||
| firewire | ||
| i2c | ||
| isa | ||
| mips | ||
| oss | ||
| parisc | ||
| pci | ||
| pcmcia | ||
| ppc | ||
| sh | ||
| soc | ||
| sparc | ||
| spi | ||
| synth | ||
| usb | ||
| ac97_bus.c | ||
| Kconfig | ||
| last.c | ||
| Makefile | ||
| sound_core.c | ||
| sound_firmware.c | ||