linux-kernel - Re: [PATCH v5 00/22] powerpc/32: Implement C syscall entry/exit

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Date:   Tue, 09 Feb 2021 11:03:21 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Michael Ellerman <mpe@...erman.id.au>, msuchanek@...e.de,
        Paul Mackerras <paulus@...ba.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v5 00/22] powerpc/32: Implement C syscall entry/exit

Excerpts from Christophe Leroy's message of February 9, 2021 1:10 am:
> This series implements C syscall entry/exit for PPC32. It reuses
> the work already done for PPC64.
> 
> This series is based on today's merge-test (b6f72fc05389e3fc694bf5a5fa1bbd33f61879e0)
> 
> In terms on performance we have the following number of cycles on an
> 8xx running null_syscall benchmark:
> - mainline: 296 cycles
> - after patch 4: 283 cycles
> - after patch 16: 304 cycles
> - after patch 17: 348 cycles
> - at the end of the series: 320 cycles
> 
> So in summary, we have a degradation of performance of 8% on null_syscall.
> 
> I think it is not a big degradation, it is worth it.

I guess it's 13% from 283. But it's very nice to use the shared C code.

There might be a few more percent speedup in there we can find later.

Thanks,
Nick