Le Wed, 13 May 2020 17:03:01 +0300,
Paul Irofti <p...@irofti.net> a écrit :
Hi,
By far one of the most popular and frequently used system calls is
clock_gettime(2). As a result the cost of kernel-userland transitions
out weight the actual work, thus I am proposing we make the data
available directly from userland without passing through a system
call.
This has been a subject of discussion multiple times across the years
and last I heard from it was at the p2k19 hackthon that I hosted in
Bucharest where espie@ sent me a diff from one of his students(?).
Being busy with organization I have not had the time to look at it and
I am thus getting back to it just now due to robert@ prodding me again
on the subject. The proposed diff is mine, not the student's.
The technical bits.
Please keep in mind that this is only proof of concept. I am looking
for ways to improve the current diff. As it is, it requires a flag day
because it makes use of ELF aux vectors to export the data from the
kernel.
I have also played with exposing the data via separate ELF sections
and with kbind-mmap alternatives. The frist also involves a flag day
and is more intrusive in my opinion, and the second I could not get
to work. I think that would be the less intrusive way of doing it,
possibly without a flag day, so if anyone knows how, please let me
know.
The supported clocks are just those that do not require process
specific data. Those can also be handled later if this diff is
decided to be a good thing.
Clock update inside the kernel is done at the end of tc_windup().
There might be better places to do it. Let me know where.
The update currently does the work of clock_gettime(), but it can
probably be changed to only update the timehands and move the logic
elsewhere. Note that if we expose only the timehands to userland, most
of the bintime functionality has to also be made available there. Or
so I think.
In userland, I wrapped the clock_gettime(2) syscall in libc. There, I
search for the auxiliary vector and fetch the timespec data from it.
As you can see in the diff, parts from the elf_exec header will have
to be exposed to userland if we do it this way.
Results.
To test this diff you need to do a full release(8). I have tested this
with multiple programs. Test programs, base programs and packages.
None the less, this diff touches many important areas of our tree and
is very fragile. I also probably missed changing some parts that
required change due to libc or elf changes.
If you see regressions, which you probably will, please let me know.
With the patch, system crashes reliably at boot when prompting for login
I followed release(8) instructions, did I miss something?
cd /sys/arch/$(machine)/compile/GENERIC.MP
make obj
make config
make && make install
reboot
cd /usrc/src
make obj
make build
sysmerge
cd /dev && ./MAKEDEV all
cd /usr/xenocara
make bootstrap
make obj
make build
reboot
I got a first panic like « panic init died (signal 0, exit 11)
when I typed reboot.
Now, if I start the system with the new kernel (old kernel.sp
still work), I get either a panic init died or I have ddb but
can't type in it. This happens after full boot sequence when
I'm prompted for login: I tried to disable all pkg_services
and xdm and it still crash at this step, I can't login.
2 screenshots of crashes errors
https://perso.pw/IMG_20200514_110104.jpg
https://perso.pw/IMG_20200514_110451.jpg
dmesg output (from bsd.sp kernel which still boots)
OpenBSD 6.7 (GENERIC) #179: Thu May 7 11:02:37 MDT 2020
dera...@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC
real mem = 8033624064 (7661MB)
avail mem = 7777611776 (7417MB)
mpath0 at root
scsibus0 at mpath0: 256 targets
mainbus0 at root
bios0 at mainbus0: SMBIOS rev. 2.7 @ 0xec070 (76 entries)
bios0: vendor American Megatrends Inc. version "FB" date 06/25/2014
bios0: Gigabyte Technology Co., Ltd. H81M-D2V
acpi0 at bios0: ACPI 5.0
acpi0: sleep states S0 S3 S4 S5
acpi0: tables DSDT FACP APIC FPDT SSDT SSDT MCFG HPET SSDT SSDT
acpi0: wakeup devices RP01(S4) PXSX(S4) PXSX(S4) RP03(S4) PXSX(S4)
RP04(S4) PXSX(S4) PXSX(S4) PXSX(S4) PXSX(S4) PXSX(S4) GLAN(S4) EHC1(S4)
EHC2(S4) XHC_(S4) HDEF(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) i3-4160 CPU @ 3.60GHz,
3592.14 MHz, 06-3c-03 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,SDBG,FMA3,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,MOVBE,POPCNT,DEADLINE,AES,XSAVE,AVX,F16C,RDRAND,NXE,PAGE1GB,RDTSCP,LONG,LAHF,ABM,PERF,ITSC,FSGSBASE,TSC_ADJUST,BMI1,AVX2,SMEP,BMI2,ERMS,INVPCID,MD_CLEAR,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=0.2.1.2.4, IBE
cpu at mainbus0: not configured
cpu at mainbus0: not configured
cpu at mainbus0: not configured
ioapic0 at mainbus0: apid 8 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 2 (RP01)
acpiprt2 at acpi0: bus 3 (RP03)
acpiprt3 at acpi0: bus 4 (RP04)
acpiprt4 at acpi0: bus 1 (PEG0)
acpiprt5 at acpi0: bus -1 (PEG1)
acpiprt6 at acpi0: bus -1 (PEG2)
acpiec0 at acpi0: not present
acpicpu0 at acpi0: C2(500@67 mwait.1@0x10), C1(1000@1 mwait.1), PSS
acpipwrres0 at acpi0: FN00, resource for FAN0
acpipwrres1 at acpi0: FN01, resource for FAN1
acpipwrres2 at acpi0: FN02, resource for FAN2
acpipwrres3 at acpi0: FN03, resource for FAN3
acpipwrres4 at acpi0: FN04, resource for FAN4
acpitz0 at acpi0: critical temperature is 105 degC
acpitz1 at acpi0: critical temperature is 105 degC
acpipci0 at acpi0 PCI0: 0x00000010 0x00000011 0x00000000
acpicmos0 at acpi0
acpibtn0 at acpi0: PWRB
"PNP0C0B" at acpi0 not configured
"PNP0C0B" at acpi0 not configured
"PNP0C0B" at acpi0 not configured
"PNP0C0B" at acpi0 not configured
"PNP0C0B" at acpi0 not configured
acpivideo0 at acpi0: GFX0
acpivout0 at acpivideo0: DD1F
cpu0: using VERW MDS workaround (except on vmm entry)
cpu0: Enhanced SpeedStep 3592 MHz: speeds: 3600, 3400, 3200, 3000,
2900, 2700, 2500, 2300, 2100, 1900, 1700, 1500, 1400, 1200, 1000, 800
MHz pci0 at mainbus0 bus 0 pchb0 at pci0 dev 0 function 0 "Intel Core
4G Host" rev 0x06 ppb0 at pci0 dev 1 function 0 "Intel Core 4G PCIE"
rev 0x06: msi pci1 at ppb0 bus 1
vendor "NVIDIA", unknown product 0x1c03 (class display subclass VGA,
rev 0xa1) at pci1 dev 0 function 0 not configured azalia0 at pci1 dev 0
function 1 vendor "NVIDIA", unknown product 0x10f1 rev 0xa1: msi
azalia0: no supported codecs inteldrm0 at pci0 dev 2 function 0 "Intel
HD Graphics 4600" rev 0x06 drm0 at inteldrm0
inteldrm0: msi, HASWELL, gen 7
azalia1 at pci0 dev 3 function 0 "Intel Core 4G HD Audio" rev 0x06: msi
azalia1: No codecs found
xhci0 at pci0 dev 20 function 0 "Intel 8 Series xHCI" rev 0x05: 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 8 Series MEI" rev 0x04 at pci0 dev 22 function
0 not configured ehci0 at pci0 dev 26 function 0 "Intel 8 Series USB"
rev 0x05: apic 8 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 azalia2 at pci0 dev 27 function 0 "Intel 8 Series HD
Audio" rev 0x05: msi azalia2: codecs: Realtek/0x0887
audio0 at azalia2
ppb1 at pci0 dev 28 function 0 "Intel 8 Series PCIE" rev 0xd5: msi
pci2 at ppb1 bus 2
ppb2 at pci0 dev 28 function 2 "Intel 8 Series PCIE" rev 0xd5: msi
pci3 at ppb2 bus 3
re0 at pci3 dev 0 function 0 "Realtek 8168" rev 0x0c: RTL8168G/8111G
(0x4c00), msi, address fc:aa:14:68:75:64 rgephy0 at re0 phy 7: RTL8251
PHY, rev. 0 ppb3 at pci0 dev 28 function 3 "Intel 8 Series PCIE" rev
0xd5: msi pci4 at ppb3 bus 4
xhci1 at pci4 dev 0 function 0 "VIA VL805 xHCI" rev 0x01: msi, xHCI 1.0
usb2 at xhci1: USB revision 3.0
uhub2 at usb2 configuration 1 interface 0 "VIA xHCI root hub" rev
3.00/1.00 addr 1 ehci1 at pci0 dev 29 function 0 "Intel 8 Series USB"
rev 0x05: apic 8 int 23 usb3 at ehci1: USB revision 2.0
uhub3 at usb3 configuration 1 interface 0 "Intel EHCI root hub" rev
2.00/1.00 addr 1 pcib0 at pci0 dev 31 function 0 "Intel H81 LPC" rev
0x05 ahci0 at pci0 dev 31 function 2 "Intel 8 Series AHCI" rev 0x05:
msi, AHCI 1.3 ahci0: port 4: 3.0Gb/s
scsibus1 at ahci0: 32 targets
sd0 at scsibus1 targ 4 lun 0: <ATA, WDC WD5000AAKX-0, 15.0>
naa.50014ee0ae3f2d32 sd0: 476940MB, 512 bytes/sector, 976773168 sectors
ichiic0 at pci0 dev 31 function 3 "Intel 8 Series SMBus" rev 0x05: apic
8 int 18 iic0 at ichiic0
spdmem0 at iic0 addr 0x50: 4GB DDR3 SDRAM PC3-12800
spdmem1 at iic0 addr 0x52: 4GB DDR3 SDRAM PC3-12800
isa0 at pcib0
isadma0 at isa0
com0 at isa0 port 0x3f8/8 irq 4: ns16550a, 16 byte fifo
pckbc0 at isa0 port 0x60/5 irq 1 irq 12
pckbd0 at pckbc0 (kbd slot)
wskbd0 at pckbd0: console keyboard
pcppi0 at isa0 port 0x61
spkr0 at pcppi0
lpt0 at isa0 port 0x378/4 irq 7
vmm0 at mainbus0: VMX/EPT
uhub4 at uhub1 port 1 configuration 1 interface 0 "Intel Rate Matching
Hub" rev 2.00/0.05 addr 2 uhub5 at uhub2 port 1 configuration 1
interface 0 "VIA Labs USB2.0 Hub" rev 2.10/4.20 addr 2 uhub6 at uhub5
port 1 configuration 1 interface 0 "ALCOR Generic USB Hub" rev
1.10/3.12 addr 3 uhidev0 at uhub6 port 1 configuration 1 interface 0
"CHERRY Mechanical Keyboard" rev 2.00/0.02 addr 4 uhidev0: iclass 3/1
ukbd0 at uhidev0: 8 variable keys, 6 key codes wskbd1 at ukbd0 mux 1
uhidev1 at uhub6 port 1 configuration 1 interface 1 "CHERRY Mechanical
Keyboard" rev 2.00/0.02 addr 4 uhidev1: iclass 3/0, 3 report ids
uhid0 at uhidev1 reportid 1: input=2, output=0, feature=0
ukbd1 at uhidev1 reportid 3: 120 variable keys, 0 key codes
wskbd2 at ukbd1 mux 1
uhidev2 at uhub6 port 1 configuration 1 interface 2 "CHERRY Mechanical
Keyboard" rev 2.00/0.02 addr 4 uhidev2: iclass 3/0
uhid1 at uhidev2: input=64, output=64, feature=64
uhidev3 at uhub6 port 2 configuration 1 interface 0 "SteelSeries Sensei
Raw Gaming Mouse" rev 1.10/1.12 addr 5 uhidev3: iclass 3/0
uhid2 at uhidev3: input=32, output=32, feature=255
uhidev4 at uhub6 port 2 configuration 1 interface 1 "SteelSeries Sensei
Raw Gaming Mouse" rev 1.10/1.12 addr 5 uhidev4: iclass 3/1
ums0 at uhidev4: 8 buttons, Z dir
wsmouse0 at ums0 mux 0
uhidev5 at uhub6 port 2 configuration 1 interface 2 "SteelSeries Sensei
Raw Gaming Mouse" rev 1.10/1.12 addr 5 uhidev5: iclass 3/1
ukbd2 at uhidev5: 8 variable keys, 6 key codes
wskbd3 at ukbd2 mux 1
uhidev6 at uhub6 port 2 configuration 1 interface 3 "SteelSeries Sensei
Raw Gaming Mouse" rev 1.10/1.12 addr 5 uhidev6: iclass 3/0
uhid3 at uhidev6: input=4, output=0, feature=0
uhidev7 at uhub6 port 3 configuration 1 interface 0 "Device 2Port
KVMSwitcher" rev 1.10/0.01 addr 6 uhidev7: iclass 3/0
ukbd3 at uhidev7: 8 variable keys, 6 key codes
wskbd4 at ukbd3 mux 1
uhidev8 at uhub6 port 3 configuration 1 interface 1 "Device 2Port
KVMSwitcher" rev 1.10/0.01 addr 6 uhidev8: no input interrupt endpoint
uhub7 at uhub3 port 1 configuration 1 interface 0 "Intel Rate Matching
Hub" rev 2.00/0.05 addr 2 vscsi0 at root
scsibus2 at vscsi0: 256 targets
softraid0 at root
scsibus3 at softraid0: 256 targets
root on sd0a (9b5c1232128549ea.a) swap on sd0b dump on sd0b
WARNING: / was not properly unmounted
inteldrm0: 1920x1080, 32bpp
wsdisplay0 at inteldrm0 mux 1: console (std, vt100 emulation), using
wskbd0 wskbd1: connecting to wsdisplay0
wskbd2: connecting to wsdisplay0
wskbd3: connecting to wsdisplay0
wskbd4: connecting to wsdisplay0
wsdisplay0: screen 1-5 added (std, vt100 emulation)
