Messages in this thread | | | Date | Thu, 12 Oct 2023 15:36:53 +0100 | From | Conor Dooley <> | Subject | Re: [PATCH v3 1/2] riscv: errata: thead: use riscv_nonstd_cache_ops for CMO |
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On Thu, Oct 12, 2023 at 10:14:55PM +0800, Jisheng Zhang wrote: > Previously, we use alternative mechanism to dynamically patch > the CMO operations for THEAD C906/C910 during boot for performance > reason. But as pointed out by Arnd, "there is already a significant > cost in accessing the invalidated cache lines afterwards, which is > likely going to be much higher than the cost of an indirect branch". > And indeed, there's no performance difference with GMAC and EMMC per > my test on Sipeed Lichee Pi 4A board. > > Use riscv_nonstd_cache_ops for THEAD C906/C910 CMO to simplify > the alternative code, and to acchieve Arnd's goal -- "I think > moving the THEAD ops at the same level as all nonstandard operations > makes sense, but I'd still leave CMO as an explicit fast path that > avoids the indirect branch. This seems like the right thing to do both > for readability and for platforms on which the indirect branch has a > noticeable overhead." > > Signed-off-by: Jisheng Zhang <jszhang@kernel.org> > Tested-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
From v2: Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Thanks, Conor. [unhandled content-type:application/pgp-signature] | |