Hi Ben,
If for performance reasons you want to set multiple registers at the same time, use the `withMRs` (e.g seL4_CallWithMRs) and other variants of the system calls. These place arguments directly into registers and avoid manipulating the IPC buffer at all (however you're limited to 4 message registers, and 1 on ia32).
Otherwise `seL4_GetMR` and friends are inline convenience functions and only manipulate the IPC buffer - the compiler should optimise these for you. They are not system calls and will not invoke the kernel.
Cheers,
Anna.
________________________________
From: Devel on behalf of Ben Ph
Sent: Tuesday, 31 March 2020 9:12 PM
To: devel@sel4.systems
Subject: [seL4] Get/Set multiple message registers with the one syscall?
I'm looking at `seL4_GetMR()` and `seL4_SetMR()`, which requires a syscall
for each get/set. To my naive eye, it seems like you're much better off
running `seL4_GetIPCBuffer()->msg` then reading/writing to each index as
needed, turning multiple syscalls (one for each get/set) into just the one.
Am I missing anything? I was planning on replacing my Get/Set calls with
direct array writes, but I'm wondering if I've missed reasons why I
shouldn't.
Thanks,
Ben
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