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john xi
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QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
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john xi
10/26/2017 11:01 PM
post118152
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QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
With the interrupt latency tool from QNX, I test my several BayTrail platforms (with J1900/E3845/E3825 processors),
all target platforms have interrupt latency issue, testing result is here:
# ./latency_500000
START: ./latency_500000, pid 102422
LOOPS: 500000
POINT: file latency.c, line 179 interrupt/schedulling latency, 999.987 Hz, 2000001383 cycles/sec
PASS: file latency.c, line 222 latency min = 1.488 usec, avg = 1.792 usec, max = 435.084 usec
STOP: ./latency_500000, pid 102422 point=1,pass=1,fail=0,xpass=0,xfail=0,unres=0
From the test result, we can see, the max value is 435.084 usec, this value is too large, the normal value should be
less than 50 usec, after change the OS version from QNX 6.5.1 to QNX 6.6/QNX7, the test result still be the same.
I run the same OS image & interrupt latency tool on other X86 platforms, such as ivyBridge/Haswell/SkyLake, the test
result is OK, max latency value will be less than 20 usec.
Further on, re-back to the BayTrail platform, if I disable the xHCI USB 3.0 Controller at BIOS, the interrupt latency
issue will disappear, test result is here:
# ./latency_500000
START: ./latency_500000, pid 69654
LOOPS: 500000
POINT: file latency.c, line 179 interrupt/schedulling latency, 999.987 Hz, 2000001383 cycles/sec
PASS: file latency.c, line 222 latency min = 1.488 usec, avg = 1.678 usec, max = 19.092 usec
STOP: ./latency_500000, pid 69654 point=1,pass=1,fail=0,xpass=0,xfail=0,unres=0
I don't know why BayTrail platform has this issue, but other X86 platform (such as ivyBridge/Haswell/SkyLake) is OK?
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Elad Lahav
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RE: QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
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Elad Lahav
10/27/2017 8:27 AM
post118153
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RE: QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
This may not be directly related to the problem you are seeing, but we found out that BayTrail boards do not keep time
accurately, which may skew the results.
--Elad
________________________________________
From: john xi [community-noreply@qnx.com]
Sent: October-26-17 11:01 PM
To: ostech-core_os
Subject: QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
With the interrupt latency tool from QNX, I test my several BayTrail platforms (with J1900/E3845/E3825 processors),
all target platforms have interrupt latency issue, testing result is here:
# ./latency_500000
START: ./latency_500000, pid 102422
LOOPS: 500000
POINT: file latency.c, line 179 interrupt/schedulling latency, 999.987 Hz, 2000001383 cycles/sec
PASS: file latency.c, line 222 latency min = 1.488 usec, avg = 1.792 usec, max = 435.084 usec
STOP: ./latency_500000, pid 102422 point=1,pass=1,fail=0,xpass=0,xfail=0,unres=0
From the test result, we can see, the max value is 435.084 usec, this value is too large, the normal value should be
less than 50 usec, after change the OS version from QNX 6.5.1 to QNX 6.6/QNX7, the test result still be the same.
I run the same OS image & interrupt latency tool on other X86 platforms, such as ivyBridge/Haswell/SkyLake, the test
result is OK, max latency value will be less than 20 usec.
Further on, re-back to the BayTrail platform, if I disable the xHCI USB 3.0 Controller at BIOS, the interrupt latency
issue will disappear, test result is here:
# ./latency_500000
START: ./latency_500000, pid 69654
LOOPS: 500000
POINT: file latency.c, line 179 interrupt/schedulling latency, 999.987 Hz, 2000001383 cycles/sec
PASS: file latency.c, line 222 latency min = 1.488 usec, avg = 1.678 usec, max = 19.092 usec
STOP: ./latency_500000, pid 69654 point=1,pass=1,fail=0,xpass=0,xfail=0,unres=0
I don't know why BayTrail platform has this issue, but other X86 platform (such as ivyBridge/Haswell/SkyLake) is OK?
_______________________________________________
OSTech
http://community.qnx.com/sf/go/post118152
To cancel your subscription to this discussion, please e-mail ostech-core_os-unsubscribe@community.qnx.com
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Albrecht Uhlmann
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Re: RE: QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
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Albrecht Uhlmann
10/27/2017 9:23 AM
post118154
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Re: RE: QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
Some ideas to think about:
- IvyBridge and Haswell: Do they have USB 3.0 support at all?
- USB, in general, is very interupt-sensitive, e.g. it causes lots of interrupts, sometimes even in idle state - it is
enough that a USB hub is present. USB 3.0 may behaving differently than USB 2.0, or the XHCI driver maybe implemented
differently regarding interrupt handling than ehci driver.
- Check interrupt assignments to PCI bus with USB 3.0 enabled and without. Maybe it's an interrupt sharing issue.
- I dont' have the source of the mentioned latency test program, check how time measurement is implemented. If
ClockCycles() is being used, you may have run in an rdtsc issue (QNX assumes this counter runs with constant speeds but
it actually doesn't on some processors, which may mean that the test itself is not accurate). The fact that the issue
disappears with some fiddeling on USB contradicts this, though.
Regards,
Albrecht
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Armin Steinhoff
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Re: QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
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Armin Steinhoff
10/28/2017 4:27 AM
post118155
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Re: QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
Albrecht Uhlmann schrieb:
> Some ideas to think about:
> - IvyBridge and Haswell: Do they have USB 3.0 support at all?
> - USB, in general, is very interupt-sensitive, e.g. it causes lots of interrupts, sometimes even in idle state - it is
enough that a USB hub is present. USB 3.0 may behaving differently than USB 2.0, or the XHCI driver maybe implemented
differently regarding interrupt handling than ehci driver.
That could be the case if the XHCI driver maybe implemented in the same
stile as the (old?) serial driver ... which does a lot of processing in
the ISR. At what hardware priority are the XHCI driver and your driver
working?
> - Check interrupt assignments to PCI bus with USB 3.0 enabled and without. Maybe it's an interrupt sharing issue.
> - I dont' have the source of the mentioned latency test program, check how time measurement is implemented. If
ClockCycles() is being used, you may have run in an rdtsc issue (QNX assumes this counter runs with constant speeds but
it actually doesn't on some processors, which may mean that the test itself is not accurate). The fact that the issue
disappears with some fiddeling on USB contradicts this, though.
>
> Regards,
> Albrecht
>
>
>
> _______________________________________________
>
> OSTech
> http://community.qnx.com/sf/go/post118154
> To cancel your subscription to this discussion, please e-mail ostech-core_os-unsubscribe@community.qnx.com
>
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john xi
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Re: QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
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john xi
10/29/2017 10:53 PM
post118157
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Re: QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
Our ivyBridge/Haswell/SkyLake boards are all have USB 3.0 Controller.
To BayTrail board & ivyBridge/Haswell/SkyLake boards, the QNX test image is the same, so the xHCI driver also be the
same.
Attached file " latency_tool_src.zip" is source code for latency tool,
another file "BayTrail with USB3.0 Enabled Test Report.pdf" is one of our customer test report for our BayTrail board
with xHCI enabled.
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john xi
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答复: RE: QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
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john xi
10/29/2017 11:20 PM
post118158
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答复: RE: QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
Our ivyBridge/Haswell/SkyLake boards are all have USB 3.0 Controller.
To BayTrail board & ivyBridge/Haswell/SkyLake boards, the QNX test image is the same, so the xHCI driver also be the
same.
Attached file " latency_tool_src.zip" is source code for latency tool,
another file "BayTrail with USB3.0 Enabled Test Report.pdf" is one of our customer test report for our BayTrail board
with xHCI enabled.
Best Regards！
John
-----邮件原件-----
发件人: Albrecht Uhlmann [mailto:community-noreply@qnx.com]
发送时间: 2017年10月27日 21:24
收件人: ostech-core_os
主题: Re: RE: QNX6.5.1/6.6/7.0 has interrupt latency issue on Intel BayTrail platform
Some ideas to think about:
- IvyBridge and Haswell: Do they have USB 3.0 support at all?
- USB, in general, is very interupt-sensitive, e.g. it causes lots of interrupts, sometimes even in idle state - it is
enough that a USB hub is present. USB 3.0 may behaving differently than USB 2.0, or the XHCI driver maybe implemented
differently regarding interrupt handling than ehci driver.
- Check interrupt assignments to PCI bus with USB 3.0 enabled and without. Maybe it's an interrupt sharing issue.
- I dont' have the source of the mentioned latency test program, check how time measurement is implemented. If
ClockCycles() is being used, you may have run in an rdtsc issue (QNX assumes this counter runs with constant speeds but
it actually doesn't on some processors, which may mean that the test itself is not accurate). The fact that the issue
disappears with some fiddeling on USB contradicts this, though.
Regards,
Albrecht
_______________________________________________
OSTech
http://community.qnx.com/sf/go/post118154
To cancel your subscription to this discussion, please e-mail ostech-core_os-unsubscribe@community.qnx.com
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