Re: Qsynth midi latency not low enough... what to do?

On Sat, Dec 01, 2018 at 01:19:00PM -0600, Adam Thompson wrote:
> PROBLEM STATEMENT: driving FluidSynth from a MIDI controller produces ~1/4sec delay between keypress and sound.
>
> NARRATIVE:
>
> I finally got Qsynth working under Xfce (it freezes X under twm!) so I can control fluidsynth in a reasonably-obvious way... but I am now experiencing substantial latency.
> The good news is that it feels just like playing an old pneumatic or tracker organ, where there's a ~0.25sec delay between keypress and sound.
> The bad news is that it feels just like playing an old pneumatic or tracker organ...
>
> I'm not a good enough musician to handle the roughly quarter-second delay when playing live. I know from many musicians that near-zero-latency from MIDI softsynths (even when using soundfonts) is possible... although no-one I know of uses OpenBSD.
>
> Is sndio(4) suitable for real-time(-ish) performance? Or do I need a (OS) platform that does ASIO or JACK? (I mostly play by ear so I'm targeting <<0.1sec latency.)
>
> If sndio core or umidi(4) support isn't the problem, the only obvious thing to blame is FluidSynth... but the CPU in this laptop should be more than up to the task, and – again – I know this particular piece of software handles low-latency live performance in other configurations (i.e. on Linux, using JACK).
> I don't suspect Qsynth at the moment, as it only controls how fluidsynth launches, it doesn't put itself in the data path.
>
> Unsurprisingly, I've been unable to find any useful information on running this kind of setup under OpenBSD. But as mentioned before, I'm trying to avoid the (to me) insanity that is JACK.
>
> Dmesg follows, just in case anyone spots anything useful in there…
>
> Hardware setup, broadly:
> * Dell Latitude E6430 laptop
> - booting in EFI mode to work around a weird bootloader bug
> * onboard azalia(4) audio (for now) using onboard speakers (for now)
> * Roland A500PRO MIDI controller, connected via USB
> * M-audio Uno USB-MIDI, nothing connected to it yet
> * No-name USB 5.1ch Audio DAC from Amazon, nothing connected to it yet
> - (leaving the M-audio umidi and the "ABC" uaudio devices disconnected makes no difference)
>
>
> Advice / pointers gratefully accepted, including pointers to documentation or threads I may have missed.
>
> Thanks,
> -Adam
>
>
> Dmesg << __EOF__ (so to speak)
> OpenBSD 6.4 (GENERIC.MP) #1: Mon Nov 26 10:18:14 CET 2018
> root@syspatch-64-amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP
> real mem = 8471482368 (8079MB)
> avail mem = 8205459456 (7825MB)
> mpath0 at root
> scsibus0 at mpath0: 256 targets
> mainbus0 at root
> bios0 at mainbus0: SMBIOS rev. 2.7 @ 0xebf40 (101 entries)
> bios0: vendor Dell Inc. version "A21" date 05/08/2017
> bios0: Dell Inc. Latitude E6430
> acpi0 at bios0: rev 2
> acpi0: sleep states S0 S3 S4 S5
> acpi0: tables DSDT FACP APIC FPDT MCFG SSDT HPET SSDT SSDT SSDT ASF! SLIC BGRT SSDT
> acpi0: wakeup devices P0P1(S4) USB1(S3) USB2(S3) USB3(S3) USB5(S3) USB6(S3) USB7(S3) PXSX(S4) RP01(S4) PXSX(S4) RP02(S4) PXSX(S4) RP05(S4) PXSX(S4) RP06(S4) PXSX(S4) [...]
> acpitimer0 at acpi0: 3579545 Hz, 24 bits
> acpimadt0 at acpi0 addr 0xfee00000: PC-AT compat
> cpu0 at mainbus0: apid 0 (boot processor)
> cpu0: Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz, 2193.29 MHz, 06-3a-09
> cpu0: FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE,SSE3,PCLMUL,DTES64,MWAIT,DS-CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,POPCNT,DEADLINE,AES,XSAVE,AVX,F16C,RDRAND,NXE,RDTSCP,LONG,LAHF,PERF,ITSC,FSGSBASE,SMEP,ERMS,IBRS,IBPB,STIBP,L1DF,SSBD,SENSOR,ARAT,XSAVEOPT,MELTDOWN
> cpu0: 256KB 64b/line 8-way L2 cache
> cpu0: smt 0, core 0, package 0
> mtrr: Pentium Pro MTRR support, 10 var ranges, 88 fixed ranges
> cpu0: apic clock running at 99MHz
> cpu0: mwait min=64, max=64, C-substates=0.2.1.1.2, IBE
> cpu1 at mainbus0: apid 2 (application processor)
> cpu1: Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz, 2192.89 MHz, 06-3a-09
> cpu1: FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE,SSE3,PCLMUL,DTES64,MWAIT,DS-CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,POPCNT,DEADLINE,AES,XSAVE,AVX,F16C,RDRAND,NXE,RDTSCP,LONG,LAHF,PERF,ITSC,FSGSBASE,SMEP,ERMS,IBRS,IBPB,STIBP,L1DF,SSBD,SENSOR,ARAT,XSAVEOPT,MELTDOWN
> cpu1: 256KB 64b/line 8-way L2 cache
> cpu1: smt 0, core 1, package 0
> cpu2 at mainbus0: apid 4 (application processor)
> cpu2: Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz, 2192.89 MHz, 06-3a-09
> cpu2: FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE,SSE3,PCLMUL,DTES64,MWAIT,DS-CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,POPCNT,DEADLINE,AES,XSAVE,AVX,F16C,RDRAND,NXE,RDTSCP,LONG,LAHF,PERF,ITSC,FSGSBASE,SMEP,ERMS,IBRS,IBPB,STIBP,L1DF,SSBD,SENSOR,ARAT,XSAVEOPT,MELTDOWN
> cpu2: 256KB 64b/line 8-way L2 cache
> cpu2: smt 0, core 2, package 0
> cpu3 at mainbus0: apid 6 (application processor)
> cpu3: Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz, 2192.89 MHz, 06-3a-09
> cpu3: FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE,SSE3,PCLMUL,DTES64,MWAIT,DS-CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,POPCNT,DEADLINE,AES,XSAVE,AVX,F16C,RDRAND,NXE,RDTSCP,LONG,LAHF,PERF,ITSC,FSGSBASE,SMEP,ERMS,IBRS,IBPB,STIBP,L1DF,SSBD,SENSOR,ARAT,XSAVEOPT,MELTDOWN
> cpu3: 256KB 64b/line 8-way L2 cache
> cpu3: smt 0, core 3, package 0
> cpu4 at mainbus0: apid 1 (application processor)
> cpu4: Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz, 2192.89 MHz, 06-3a-09
> cpu4: FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE,SSE3,PCLMUL,DTES64,MWAIT,DS-CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,POPCNT,DEADLINE,AES,XSAVE,AVX,F16C,RDRAND,NXE,RDTSCP,LONG,LAHF,PERF,ITSC,FSGSBASE,SMEP,ERMS,IBRS,IBPB,STIBP,L1DF,SSBD,SENSOR,ARAT,XSAVEOPT,MELTDOWN
> cpu4: 256KB 64b/line 8-way L2 cache
> cpu4: smt 1, core 0, package 0
> cpu5 at mainbus0: apid 3 (application processor)
> cpu5: Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz, 2192.89 MHz, 06-3a-09
> cpu5: FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE,SSE3,PCLMUL,DTES64,MWAIT,DS-CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,POPCNT,DEADLINE,AES,XSAVE,AVX,F16C,RDRAND,NXE,RDTSCP,LONG,LAHF,PERF,ITSC,FSGSBASE,SMEP,ERMS,IBRS,IBPB,STIBP,L1DF,SSBD,SENSOR,ARAT,XSAVEOPT,MELTDOWN
> cpu5: 256KB 64b/line 8-way L2 cache
> cpu5: smt 1, core 1, package 0
> cpu6 at mainbus0: apid 5 (application processor)
> cpu6: Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz, 2192.89 MHz, 06-3a-09
> cpu6: FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE,SSE3,PCLMUL,DTES64,MWAIT,DS-CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,POPCNT,DEADLINE,AES,XSAVE,AVX,F16C,RDRAND,NXE,RDTSCP,LONG,LAHF,PERF,ITSC,FSGSBASE,SMEP,ERMS,IBRS,IBPB,STIBP,L1DF,SSBD,SENSOR,ARAT,XSAVEOPT,MELTDOWN
> cpu6: 256KB 64b/line 8-way L2 cache
> cpu6: smt 1, core 2, package 0
> cpu7 at mainbus0: apid 7 (application processor)
> cpu7: Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz, 2192.89 MHz, 06-3a-09
> cpu7: FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE,SSE3,PCLMUL,DTES64,MWAIT,DS-CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,POPCNT,DEADLINE,AES,XSAVE,AVX,F16C,RDRAND,NXE,RDTSCP,LONG,LAHF,PERF,ITSC,FSGSBASE,SMEP,ERMS,IBRS,IBPB,STIBP,L1DF,SSBD,SENSOR,ARAT,XSAVEOPT,MELTDOWN
> cpu7: 256KB 64b/line 8-way L2 cache
> cpu7: smt 1, core 3, package 0
> ioapic0 at mainbus0: apid 2 pa 0xfec00000, version 20, 24 pins
> acpimcfg0 at acpi0
> acpimcfg0: addr 0xf8000000, bus 0-63
> acpihpet0 at acpi0: 14318179 Hz
> acpiprt0 at acpi0: bus 0 (PCI0)
> acpiprt1 at acpi0: bus -1 (P0P1)
> acpiprt2 at acpi0: bus 2 (RP01)
> acpiprt3 at acpi0: bus 3 (RP02)
> acpiprt4 at acpi0: bus -1 (RP05)
> acpiprt5 at acpi0: bus 12 (RP06)
> acpiprt6 at acpi0: bus -1 (RP07)
> acpiprt7 at acpi0: bus -1 (RP08)
> acpiprt8 at acpi0: bus 1 (PEG0)
> acpiprt9 at acpi0: bus -1 (PEG1)
> acpiprt10 at acpi0: bus -1 (PEG2)
> acpiprt11 at acpi0: bus -1 (PEG3)
> acpiprt12 at acpi0: bus 4 (RP03)
> acpiprt13 at acpi0: bus 8 (RP04)
> acpiec0 at acpi0
> acpicpu0 at acpi0: C3(200@87 mwait.1@0x30), C2(500@59 mwait.1@0x10), C1(1000@1 mwait.1), PSS
> acpicpu1 at acpi0: C3(200@87 mwait.1@0x30), C2(500@59 mwait.1@0x10), C1(1000@1 mwait.1), PSS
> acpicpu2 at acpi0: C3(200@87 mwait.1@0x30), C2(500@59 mwait.1@0x10), C1(1000@1 mwait.1), PSS
> acpicpu3 at acpi0: C3(200@87 mwait.1@0x30), C2(500@59 mwait.1@0x10), C1(1000@1 mwait.1), PSS
> acpicpu4 at acpi0: C3(200@87 mwait.1@0x30), C2(500@59 mwait.1@0x10), C1(1000@1 mwait.1), PSS
> acpicpu5 at acpi0: C3(200@87 mwait.1@0x30), C2(500@59 mwait.1@0x10), C1(1000@1 mwait.1), PSS
> acpicpu6 at acpi0: C3(200@87 mwait.1@0x30), C2(500@59 mwait.1@0x10), C1(1000@1 mwait.1), PSS
> acpicpu7 at acpi0: C3(200@87 mwait.1@0x30), C2(500@59 mwait.1@0x10), C1(1000@1 mwait.1), PSS
> acpitz0 at acpi0: critical temperature is 107 degC
> acpicmos0 at acpi0
> "SMO8810" at acpi0 not configured
> "*pnp0c14" at acpi0 not configured
> acpibtn0 at acpi0: LID0
> acpibtn1 at acpi0: PBTN
> acpibtn2 at acpi0: SBTN
> acpiac0 at acpi0: AC unit online
> acpibat0 at acpi0: BAT0 model "DELL P6YD623" serial 1827 type LION oem "SMP"
> acpibat1 at acpi0: BAT1 not present
> acpibat2 at acpi0: BAT2 not present
> "DELLABCE" at acpi0 not configured
> "INT33A0" at acpi0 not configured
> acpivideo0 at acpi0: VID_
> acpivout0 at acpivideo0: LCD_
> acpivideo1 at acpi0: VID_
> acpivout at acpivideo1 not configured
> cpu0: Enhanced SpeedStep 2193 MHz: speeds: 2201, 2200, 2100, 2000, 1900, 1800, 1700, 1600, 1500, 1400, 1300, 1200 MHz
> pci0 at mainbus0 bus 0
> pchb0 at pci0 dev 0 function 0 "Intel Core 3G Host" rev 0x09
> ppb0 at pci0 dev 1 function 0 "Intel Core 3G PCIE" rev 0x09: msi
> pci1 at ppb0 bus 1
> vendor "NVIDIA", unknown product 0x0dfc (class display subclass VGA, rev 0xa1) at pci1 dev 0 function 0 not configured
> inteldrm0 at pci0 dev 2 function 0 "Intel HD Graphics 4000" rev 0x09
> drm0 at inteldrm0
> inteldrm0: msi
> inteldrm0: 1600x900, 32bpp
> wsdisplay0 at inteldrm0 mux 1: console (std, vt100 emulation)
> wsdisplay0: screen 1-5 added (std, vt100 emulation)
> xhci0 at pci0 dev 20 function 0 "Intel 7 Series xHCI" rev 0x04: msi, xHCI 1.0
> usb0 at xhci0: USB revision 3.0
> uhub0 at usb0 configuration 1 interface 0 "Intel xHCI root hub" rev 3.00/1.00 addr 1
> "Intel 7 Series MEI" rev 0x04 at pci0 dev 22 function 0 not configured
> puc0 at pci0 dev 22 function 3 "Intel 7 Series KT" rev 0x04: ports: 16 com
> com4 at puc0 port 0 apic 2 int 19: ns16550a, 16 byte fifo
> com4: probed fifo depth: 0 bytes
> em0 at pci0 dev 25 function 0 "Intel 82579LM" rev 0x04: msi, address b8:ca:3a:d0:d9:42
> ehci0 at pci0 dev 26 function 0 "Intel 7 Series USB" rev 0x04: apic 2 int 16
> usb1 at ehci0: USB revision 2.0
> uhub1 at usb1 configuration 1 interface 0 "Intel EHCI root hub" rev 2.00/1.00 addr 1
> azalia0 at pci0 dev 27 function 0 "Intel 7 Series HD Audio" rev 0x04: msi
> azalia0: codecs: IDT/0x76df
> audio0 at azalia0
> ppb1 at pci0 dev 28 function 0 "Intel 7 Series PCIE" rev 0xc4: msi
> pci2 at ppb1 bus 2
> ppb2 at pci0 dev 28 function 1 "Intel 7 Series PCIE" rev 0xc4: msi
> pci3 at ppb2 bus 3
> iwn0 at pci3 dev 0 function 0 "Intel Centrino Advanced-N 6205" rev 0x34: msi, MIMO 2T2R, MoW, address 84:3a:4b:4b:1c:18
> ppb3 at pci0 dev 28 function 2 "Intel 7 Series PCIE" rev 0xc4: msi
> pci4 at ppb3 bus 4
> ppb4 at pci0 dev 28 function 3 "Intel 7 Series PCIE" rev 0xc4: msi
> pci5 at ppb4 bus 8
> ppb5 at pci0 dev 28 function 5 "Intel 7 Series PCIE" rev 0xc4: msi
> pci6 at ppb5 bus 12
> sdhc0 at pci6 dev 0 function 0 vendor "O2 Micro", unknown product 0x8221 rev 0x05: apic 2 int 17
> sdhc0: SDHC 2.0, 50 MHz base clock
> sdmmc0 at sdhc0: 4-bit, sd high-speed, mmc high-speed, dma
> ehci1 at pci0 dev 29 function 0 "Intel 7 Series USB" rev 0x04: apic 2 int 21
> usb2 at ehci1: USB revision 2.0
> uhub2 at usb2 configuration 1 interface 0 "Intel EHCI root hub" rev 2.00/1.00 addr 1
> pcib0 at pci0 dev 31 function 0 "Intel QM77 LPC" rev 0x04
> ahci0 at pci0 dev 31 function 2 "Intel 7 Series AHCI" rev 0x04: msi, AHCI 1.3
> ahci0: port 0: 6.0Gb/s
> ahci0: port 1: 1.5Gb/s
> scsibus1 at ahci0: 32 targets
> sd0 at scsibus1 targ 0 lun 0: <ATA, INTEL SSDSC2BW24, DC32> SCSI3 0/direct fixed naa.55cd2e404bfa7767
> sd0: 228936MB, 512 bytes/sector, 468862128 sectors, thin
> cd0 at scsibus1 targ 1 lun 0: <HL-DT-ST, DVD+-RW GU40N, A104> ATAPI 5/cdrom removable
> ichiic0 at pci0 dev 31 function 3 "Intel 7 Series SMBus" rev 0x04: apic 2 int 18
> iic0 at ichiic0
> iic0: addr 0x29 07=ff 0f=33 10=8f 11=80 12=b7 13=51 14=b3 15=33 16=1e 17=24 18=1d 19=a0 1a=50 1b=64 1c=c0 1e=20 20=7f 22=40 27=ff 29=fe 2d=43 2f=20 30=95 31=25 32=0e 33=16 87=ff 8f=33 90=8f 91=80 92=b7 93=51 94=b3 95=33 96=1e 97=24 98=1d 99=a0 9a=50 9b=64 9c=c0 9e=20 a0=7f a2=40 a7=ff a9=fd ad=44 af=20 b0=95 b1=25 b2=0e b3=16 words 00=0000 01=0000 02=0000 03=0000 04=0000 05=0000 06=0000 07=ffff
> spdmem0 at iic0 addr 0x50: 4GB DDR3 SDRAM PC3-10600 SO-DIMM
> spdmem1 at iic0 addr 0x52: 4GB DDR3 SDRAM PC3-10600 SO-DIMM
> isa0 at pcib0
> isadma0 at isa0
> pckbc0 at isa0 port 0x60/5 irq 1 irq 12
> pckbd0 at pckbc0 (kbd slot)
> wskbd0 at pckbd0: console keyboard, using wsdisplay0
> pms0 at pckbc0 (aux slot)
> wsmouse0 at pms0 mux 0
> pcppi0 at isa0 port 0x61
> spkr0 at pcppi0
> vmm0 at mainbus0: VMX/EPT
> efifb at mainbus0 not configured
> error: [drm:pid0:cpt_set_fifo_underrun_reporting] *ERROR* uncleared pch fifo underrun on pch transcoder A
> error: [drm:pid0:intel_pch_fifo_underrun_irq_handler] *ERROR* PCH transcoder A FIFO underrun
> uaudio0 at uhub0 port 1 configuration 1 interface 0 "ABC USB Sound Device" rev 1.10/0.10 addr 2
> uaudio0: audio rev 1.00, 14 mixer controls
> audio1 at uaudio0
> uhidev0 at uhub0 port 1 configuration 1 interface 3 "ABC USB Sound Device" rev 1.10/0.10 addr 2
> uhidev0: iclass 3/0
> uhid0 at uhidev0: input=3, output=4, feature=0
> umidi0 at uhub0 port 3 configuration 1 interface 1 "M-Audio USB Uno MIDI Interface" rev 1.00/1.13 addr 3
> umidi0: (genuine USB-MIDI)
> umidi0: out=1, in=1
> midi0 at umidi0: <USB MIDI I/F>
> ugen0 at uhub0 port 3 configuration 1 "M-Audio USB Uno MIDI Interface" rev 1.00/1.13 addr 3
> uhub3 at uhub1 port 1 configuration 1 interface 0 "Intel Rate Matching Hub" rev 2.00/0.00 addr 2
> umidi1 at uhub3 port 2 configuration 1 interface 1 "Roland A-PRO" rev 1.10/1.00 addr 3
> umidi1: (genuine USB-MIDI)
> umidi1: out=2, in=3
> midi1 at umidi1: <USB MIDI I/F>
> midi2 at umidi1: <USB MIDI I/F>
> midi3 at umidi1: <USB MIDI I/F>
> ugen1 at uhub3 port 2 configuration 1 "Roland A-PRO" rev 1.10/1.00 addr 3
> ugen2 at uhub3 port 4 "Broadcom Corp BCM20702A0" rev 2.00/1.12 addr 4
> uvideo0 at uhub3 port 5 configuration 1 interface 0 "CNFB183J0150200001D2 Laptop_Integrated_Webcam_E4HD" rev 2.00/28.07 addr 5
> video0 at uvideo0
> uhub4 at uhub2 port 1 configuration 1 interface 0 "Intel Rate Matching Hub" rev 2.00/0.00 addr 2
> vscsi0 at root
> scsibus2 at vscsi0: 256 targets
> softraid0 at root
> scsibus3 at softraid0: 256 targets
> root on sd0a (9e659ad49c8fff3e.a) swap on sd0b dump on sd0b
> error: [drm:pid97912:intel_pipe_update_start] *ERROR* Potential atomic update failure on pipe A
>

May I suggest as a test to see how LMMS's soundfont player works for you. That
would separate qsynth vs the machine itself or some other config. I have found
lmms + sndio to yield perfectly good realtime playable results with an external
midi keyboard in the sf player as well as other synths. Note you have to set the
deault midi in for lmms before runing it due to the sndio implementation in
lmms. I got that answer over the mailing list a month or so ago so you can go
back in history to find it.

Ken