diff options
author | Konstantin Ozerkov <kozerkov@parallels.com> | 2011-10-26 15:11:01 (GMT) |
---|---|---|
committer | Takashi Iwai <tiwai@suse.de> | 2011-10-31 09:03:28 (GMT) |
commit | 228cf79376f13b98f2e1ac10586311312757675c (patch) | |
tree | d6855298c13b11deba6426b736d23d4aeeb1bdd3 | |
parent | c09403dcc5698abf214329fbbf3cf8dbb5558bea (diff) | |
download | linux-fsl-qoriq-228cf79376f13b98f2e1ac10586311312757675c.tar.xz |
ALSA: intel8x0: Improve performance in virtual environment
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>
-rw-r--r-- | sound/pci/intel8x0.c | 29 |
1 files changed, 27 insertions, 2 deletions
diff --git a/sound/pci/intel8x0.c b/sound/pci/intel8x0.c index 6a5b387..6dc302c 100644 --- a/sound/pci/intel8x0.c +++ b/sound/pci/intel8x0.c @@ -42,6 +42,12 @@ #include <asm/pgtable.h> #include <asm/cacheflush.h> +#ifdef CONFIG_KVM_GUEST +#include <asm/kvm_para.h> +#else +#define kvm_para_available() (0) +#endif + MODULE_AUTHOR("Jaroslav Kysela <perex@perex.cz>"); MODULE_DESCRIPTION("Intel 82801AA,82901AB,i810,i820,i830,i840,i845,MX440; SiS 7012; Ali 5455"); MODULE_LICENSE("GPL"); @@ -77,6 +83,7 @@ static int buggy_semaphore; static int buggy_irq = -1; /* auto-check */ static int xbox; static int spdif_aclink = -1; +static int inside_vm = -1; module_param(index, int, 0444); MODULE_PARM_DESC(index, "Index value for Intel i8x0 soundcard."); @@ -94,6 +101,8 @@ module_param(xbox, bool, 0444); MODULE_PARM_DESC(xbox, "Set to 1 for Xbox, if you have problems with the AC'97 codec detection."); module_param(spdif_aclink, int, 0444); MODULE_PARM_DESC(spdif_aclink, "S/PDIF over AC-link."); +module_param(inside_vm, bool, 0444); +MODULE_PARM_DESC(inside_vm, "KVM/Parallels optimization."); /* just for backward compatibility */ static int enable; @@ -400,6 +409,7 @@ struct intel8x0 { unsigned buggy_irq: 1; /* workaround for buggy mobos */ unsigned xbox: 1; /* workaround for Xbox AC'97 detection */ unsigned buggy_semaphore: 1; /* workaround for buggy codec semaphore */ + unsigned inside_vm: 1; /* enable VM optimization */ int spdif_idx; /* SPDIF BAR index; *_SPBAR or -1 if use PCMOUT */ unsigned int sdm_saved; /* SDM reg value */ @@ -1065,8 +1075,11 @@ static snd_pcm_uframes_t snd_intel8x0_pcm_pointer(struct snd_pcm_substream *subs udelay(10); continue; } - if (civ == igetbyte(chip, ichdev->reg_offset + ICH_REG_OFF_CIV) && - ptr1 == igetword(chip, ichdev->reg_offset + ichdev->roff_picb)) + if (civ != igetbyte(chip, ichdev->reg_offset + ICH_REG_OFF_CIV)) + continue; + if (chip->inside_vm) + break; + if (ptr1 == igetword(chip, ichdev->reg_offset + ichdev->roff_picb)) break; } while (timeout--); ptr = ichdev->last_pos; @@ -2984,6 +2997,10 @@ static int __devinit snd_intel8x0_create(struct snd_card *card, if (xbox) chip->xbox = 1; + chip->inside_vm = inside_vm; + if (inside_vm) + printk(KERN_INFO "intel8x0: enable KVM optimization\n"); + if (pci->vendor == PCI_VENDOR_ID_INTEL && pci->device == PCI_DEVICE_ID_INTEL_440MX) chip->fix_nocache = 1; /* enable workaround */ @@ -3226,6 +3243,14 @@ static int __devinit snd_intel8x0_probe(struct pci_dev *pci, buggy_irq = 0; } + if (inside_vm < 0) { + /* detect KVM and Parallels virtual environments */ + inside_vm = kvm_para_available(); +#if defined(__i386__) || defined(__x86_64__) + inside_vm = inside_vm || boot_cpu_has(X86_FEATURE_HYPERVISOR); +#endif + } + if ((err = snd_intel8x0_create(card, pci, pci_id->driver_data, &chip)) < 0) { snd_card_free(card); |