Revision 228cf79376f13b98f2e1ac10586311312757675c authored by Konstantin Ozerkov on 26 October 2011, 15:11:01 UTC, committed by Takashi Iwai on 31 October 2011, 09:03:28 UTC
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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File | Mode | Size |
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Documentation | ||
arch | ||
block | ||
crypto | ||
drivers | ||
firmware | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.gitignore | -rw-r--r-- | 1014 bytes |
.mailmap | -rw-r--r-- | 4.1 KB |
COPYING | -rw-r--r-- | 18.3 KB |
CREDITS | -rw-r--r-- | 92.6 KB |
Kbuild | -rw-r--r-- | 2.4 KB |
Kconfig | -rw-r--r-- | 252 bytes |
MAINTAINERS | -rw-r--r-- | 196.4 KB |
Makefile | -rw-r--r-- | 52.3 KB |
README | -rw-r--r-- | 17.0 KB |
REPORTING-BUGS | -rw-r--r-- | 3.3 KB |
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