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What PMU Events describes Remote Reads

FabianSchuetze

I would like to know how what perf counters describe remote memory loads from other cores or nodes. The Arm Cortex A-Series, Programmer's Guide for Arm v8-a (https://cs140e.sergio.bz/docs/ARMv8-A-Programmer-Guide.pdf, would be nice to know the official link to that document too)says (at 11-7):

> For multi-core and multi-cluster systems, before performing a load from external memory, the caches of L2 or L1 caches of cores within the cluster or of other clusters might also be checked

What perf counters describe such loads?

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  • +1

    Hi ,

    The Arm Architecture Reference Manual for A-profile architecture chapter D13.12.3.2 Common microarchitectural events lists many events, which might be of interest. For example:

    • 0x0031, REMOTE_ACCESS, Access to a remote device
    • 0x0038, REMOTE_ACCESS_RD, Access to a remote device, read
    • 0x8194, DSNP_HIT_RD, Snoop hit, demand data read
    • 0x8195, DSNP_HIT_NEAR_RD, Snoop hit in near local cache, demand data read
    • 0x8196, DSNP_HIT_FAR_RD, Snoop hit in far local cache, demand data read
    • 0x8197, DSNP_HIT_REMOTE_RD, Snoop hit in remote cache, demand data read
    • 0x8238, REMOTE_MEM, Access to memory attached to a remote device

    etc.

    You will need to verify if your system does indeed implement those events, though.

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  • +1

    Hi ,

    The Arm Architecture Reference Manual for A-profile architecture chapter D13.12.3.2 Common microarchitectural events lists many events, which might be of interest. For example:

    • 0x0031, REMOTE_ACCESS, Access to a remote device
    • 0x0038, REMOTE_ACCESS_RD, Access to a remote device, read
    • 0x8194, DSNP_HIT_RD, Snoop hit, demand data read
    • 0x8195, DSNP_HIT_NEAR_RD, Snoop hit in near local cache, demand data read
    • 0x8196, DSNP_HIT_FAR_RD, Snoop hit in far local cache, demand data read
    • 0x8197, DSNP_HIT_REMOTE_RD, Snoop hit in remote cache, demand data read
    • 0x8238, REMOTE_MEM, Access to memory attached to a remote device

    etc.

    You will need to verify if your system does indeed implement those events, though.

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