Messages in this thread |  | | From | Florian Weimer <> | Subject | Re: Candidate Linux ABI for Intel AMX and hypothetical new related features | Date | Sat, 22 May 2021 09:16:44 +0200 |
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* Len Brown:
> A. per-task. If we do it this way, then we will likely wind up > mandating a GET at the start of every routine in every library that > touches AMX, and potentially also a PUT. This is because the library > has no idea what thread called it. The plus is that this will address > the "used once and sits on a buffer for the rest of the process > lifetime' scenario. The minus is that high performance users will be > executing thousands of unnecessary system calls that have zero value.
We could revive the KTLS proposal (userspace donates memory for use by the kernel & vDSO), and the thread could reserve (on-stack) buffer space for kernel use for the duration of the AMX computation. There would be a pointer to that space in the KTLS area, set upon entry of the AMX region, and cleared upon exit. It's not extremely cheap (unbounded alloca has a stack probing loop nowadays). But no system call is required.
Thanks, Florian
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