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Date: Sat, 07 Jun 2008 11:38:19 +0200 From: Takashi Iwai <tiwai@...e.de> To: Benjamin Kidwell <benjkidwell@...oo.com> Cc: linux-kernel@...r.kernel.org Subject: Re: Linux-next Alsa hda_intel events/0 high CPU usage, bisected At Fri, 6 Jun 2008 14:07:55 -0700 (PDT), Benjamin Kidwell wrote: > > Linux-next Alsa hda_intel events/0 high CPU usage, bisected > > During sound playback with recent linux-next-20080806 I observed much higher > than usual cpu usage for the events/0 process, locked at a near constant 4.3% > according to ps. 2.6.25-rc5 does not exhibit this behavior on my machine. > > I git-bisected and arrived at this commit to sound/pci/hda/hda_intel.c > 8a4bd4dff53ad23c32ffc0b366e592319dd566a4 > which fixes IRQ timing issues. > > As a very crude debugging test, I short-circuited this decision: > > --- a/sound/pci/hda/hda_intel.c > +++ b/sound/pci/hda/hda_intel.c > @@ -1489,7 +1489,7 @@ > } > > if (pos % azx_dev->period_bytes > azx_dev->period_bytes / 2) > - return 0; /* NG - it's below the period boundary */ > + return 1; /* Tell a lie */ > return 1; /* OK, it's fine */ > } > > and sure enough, the events/0 process cpu load dropped down to its usual > level, undetectable with top and ps. I don't know if the high events/0 load is > the intended behavior of this code on my hardware or not. Sound playback and > general system behavior seemed subjectively equivalent regardless of the > highly active events/0 process. The problem is that your hardware reports the wrong DMA position. Some apps don't care about the exact position, but some do. The latter apps (such as JACK running with two periods) suffer from this bug severely. I didn't expect that this delay is so much, (IOW, the hardware is so buggy). Maybe it should be put into its own workq. Also, you can replace cond_resched() with msleep(1) in azx_irq_pending_work() as well. Takashi > This report is from /dev/random_user and I'm not qualified to diff bugs vs. > features, so sorry if this message is just noise. I'm happy to provide more > info if needed. > > Here's a bit of relevant info from my machine from a run with the high > events/0 usage. A few bits of dmesg: > > [ 0.066419] ACPI: Core revision 20080321 > [ 0.075988] ENABLING IO-APIC IRQs > [ 0.075988] ..TIMER: vector=0x31 apic1=0 pin1=2 apic2=-1 pin2=-1 > [ 0.075988] ..MP-BIOS bug: 8254 timer not connected to IO-APIC > [ 0.075988] ...trying to set up timer (IRQ0) through the 8259A ... > failed. > [ 0.075988] ...trying to set up timer as Virtual Wire IRQ... works. > [ 0.086170] CPU0: Intel(R) Pentium(R) 4 CPU 3.00GHz stepping 09 > [ 0.086986] CPU 1 irqstacks, hard=c0359000 soft=c0357000 > [ 0.086986] Booting processor 1/1 ip 6000 > [ 0.096985] Initializing CPU#1 > [ 0.096985] Calibrating delay using timer specific routine.. 5998.67 > BogoMIPS (lpj=2999338) > [ 0.160975] ACPI: bus type pci registered > [ 0.160975] PCI: MCFG configuration 0: base e0000000 segment 0 buses > 0 - > 255 > [ 0.160975] PCI: MCFG area at e0000000 reserved in E820 > [ 0.160975] PCI: Using MMCONFIG for extended config space > [ 0.160975] PCI: Using configuration type 1 for base access > [ 0.160975] Setting up standard PCI resources > [ 0.166580] ACPI: EC: Look up EC in DSDT > [ 0.172973] ACPI: Interpreter enabled > [ 0.172977] ACPI: (supports S0 S3 S5) > [ 0.173185] ACPI: Using IOAPIC for interrupt routing > [ 0.179736] ACPI: PCI Root Bridge [PCI0] (0000:00) > [ 0.180460] PCI: Transparent bridge - 0000:00:14.4 > [ 0.180566] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT] > [ 0.180972] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0.P2P_._PRT] > [ 0.194970] ACPI: PCI Interrupt Link [LNKA] (IRQs 3 4 5 6 7 10 11) > *0, disabled. > [ 0.195606] ACPI: PCI Interrupt Link [LNKB] (IRQs 3 4 5 6 7 10 11) > *0, disabled. > [ 0.196309] ACPI: PCI Interrupt Link [LNKC] (IRQs 3 4 5 6 7 10 11) > *0, disabled. > [ 0.197026] ACPI: PCI Interrupt Link [LNKD] (IRQs 3 4 5 6 7 10 11) > *0, disabled. > [ 0.197969] ACPI: PCI Interrupt Link [LNKE] (IRQs 3 4 5 6 *7 10 11) > [ 0.198286] ACPI: PCI Interrupt Link [LNKF] (IRQs 3 4 5 6 7 10 11) > *0, disabled. > [ 0.198989] ACPI: PCI Interrupt Link [LNK0] (IRQs 3 4 5 6 7 10 *11) > [ 0.199567] ACPI: PCI Interrupt Link [LNK1] (IRQs 3 4 *5 6 7 10 11) > [ 17.037709] piix4_smbus 0000:00:14.0: Found 0000:00:14.0 device > [ 17.135812] ACPI: PCI Interrupt 0000:00:14.2[A] -> GSI 16 (level, > low) -> IRQ 16 > [ 27.183697] hda-intel: Invalid position buffer, using LPIB read > method instead. > > output of lsmod: > > ipv6 223300 12 > cpufreq_userspace 2988 0 > cpufreq_stats 4748 0 > cpufreq_powersave 1792 0 > cpufreq_ondemand 6796 0 > freq_table 3592 2 cpufreq_stats,cpufreq_ondemand > sbs 11144 0 > sbshc 4864 1 sbs > container 3456 0 > battery 10116 0 > iptable_filter 2688 0 > ip_tables 9872 1 iptable_filter > x_tables 12164 1 ip_tables > ac 4228 0 > loop 13452 0 > af_packet 15232 2 > snd_hda_intel 55692 3 > snd_pcm 62084 1 snd_hda_intel > snd_timer 18312 1 snd_pcm > serio_raw 5124 0 > snd 39092 9 snd_hda_intel,snd_pcm,snd_timer > psmouse 23432 0 > i2c_piix4 7696 0 > soundcore 5984 1 snd > snd_page_alloc 7304 2 snd_hda_intel,snd_pcm > i2c_core 18324 1 i2c_piix4 > ati_agp 6540 0 > agpgart 26312 1 ati_agp > button 6032 0 > evdev 8704 3 > ext3 116616 1 > jbd 39828 1 ext3 > mbcache 6404 1 ext3 > usbhid 19364 0 > hid 36096 1 usbhid > ide_cd_mod 29444 0 > cdrom 33056 1 ide_cd_mod > sd_mod 20760 3 > pata_atiixp 4608 0 > 8139too 20992 0 > 8139cp 17408 0 > mii 4480 2 8139too,8139cp > atiixp 3588 0 [permanent] > ehci_hcd 31372 0 > ohci_hcd 20228 0 > sata_sil 7560 2 > pata_acpi 3968 0 > ata_generic 4868 0 > usbcore 120176 4 usbhid,ehci_hcd,ohci_hcd > libata 139616 4 > pata_atiixp,sata_sil,pata_acpi,ata_generic > scsi_mod 85448 2 sd_mod,libata > dock 7824 1 libata > ide_pci_generic 4100 0 [permanent] > ide_core 84904 3 ide_cd_mod,atiixp,ide_pci_generic > thermal 15004 0 > processor 31424 1 thermal > fan 4228 0 > fuse 45468 3 > > audio entry snipped from lspci -vvv > 00:14.2 Audio device: ATI Technologies Inc IXP SB4x0 High Definition > Audio Controller (rev 01) > Subsystem: Micro-Star International Co., Ltd. Unknown device 725a > Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- > ParErr- Stepping- SERR- FastB2B- > Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=slow >TAbort- > <TAbort- <MAbort- >SERR- <PERR- > Latency: 64, Cache Line Size: 32 bytes > Interrupt: pin ? routed to IRQ 16 > Region 0: Memory at fdff4000 (64-bit, non-prefetchable) > [size=16K] > Capabilities: [50] Power Management version 2 > Flags: PMEClk- DSI- D1- D2- AuxCurrent=55mA > PME(D0+,D1-,D2-,D3hot+,D3cold+) > Status: D0 PME-Enable- DSel=0 DScale=0 PME- > Capabilities: [60] Message Signalled Interrupts: Mask- 64bit+ > Queue=0/0 Enable- > Address: 0000000000000000 Data: 0000 > > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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