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A comment on Magic-trace – High-resolution traces of what a process is doing. Parent comment

Re:Magic-trace – High-resolution traces of what a process is... by b20000 on Friday April 22, 2022 @04:48PM (#31127888)
how do you access this DDIO feature if you are writing a C or C++ application? intrinsics?
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Re:Magic-trace – High-resolution traces of what a process is... by tbr1 on Friday April 22, 2022 @05:09PM (#31128168)
DDIO operates mostly transparently to software, with the I/O controller feeding DMAs into a slice of L3. Hardware can opt out by setting PCIe TLP header hints, and you have some system-wide configurability via MSRs, but it's not something a userspace application can take into its own hands.
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Re:Magic-trace – High-resolution traces of what a process is... by b20000 on Friday April 22, 2022 @06:23PM (#31128962)
so is this taken advantage of by the OnLoad drivers of solarflare cards, for example?
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Re:Magic-trace – High-resolution traces of what a process is... by isogon on Sunday April 24, 2022 @01:18PM (#31146057)
Noticed this just now. It is.
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Re:Magic-trace – High-resolution traces of what a process is... by medawsonjr on Monday April 25, 2022 @01:56PM (#31158412)
It's configurable via MSR. You can also disable it system-wide or on a PCIe port basis. I detailed it all here:

https://www.jabperf.com/skip-the-line-with-intel-ddio/

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