linux-kernel - Re: [PATCH v5 0/5] Wire up getrandom() vDSO implementation on powerpc

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Message-ID: <Zthr1nB_RJ56YD3O@zx2c4.com>
Date: Wed, 4 Sep 2024 16:16:54 +0200
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Naveen N Rao <naveen@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-kselftest@...r.kernel.org,
	llvm@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, linux-trace-kernel@...r.kernel.org,
	Adhemerval Zanella <adhemerval.zanella@...aro.org>,
	Xi Ruoyao <xry111@...111.site>
Subject: Re: [PATCH v5 0/5] Wire up getrandom() vDSO implementation on powerpc

Hi Christophe, Michael,

On Mon, Sep 02, 2024 at 09:17:17PM +0200, Christophe Leroy wrote:
> This series wires up getrandom() vDSO implementation on powerpc.
> 
> Tested on PPC32 on real hardware.
> Tested on PPC64 (both BE and LE) on QEMU:
> 
> Performance on powerpc 885:
> 	~# ./vdso_test_getrandom bench-single
> 	   vdso: 25000000 times in 62.938002291 seconds
> 	   libc: 25000000 times in 535.581916866 seconds
> 	syscall: 25000000 times in 531.525042806 seconds
> 
> Performance on powerpc 8321:
> 	~# ./vdso_test_getrandom bench-single
> 	   vdso: 25000000 times in 16.899318858 seconds
> 	   libc: 25000000 times in 131.050596522 seconds
> 	syscall: 25000000 times in 129.794790389 seconds
> 
> Performance on QEMU pseries:
> 	~ # ./vdso_test_getrandom bench-single
> 	   vdso: 25000000 times in 4.977777162 seconds
> 	   libc: 25000000 times in 75.516749981 seconds
> 	syscall: 25000000 times in 86.842242014 seconds

Looking good. I have no remaining nits on this patchset; it looks good
to me.

A review from Michael would be nice though (in addition to the necessary
"Ack" I need to commit this to my tree), because there are a lot of PPC
particulars that I don't know enough about to review properly. For
example, you use -ffixed-r30 on PPC64. I'm sure there's a good reason
for this, but I don't know enough to assess it. And cvdso_call I have no
idea what's going on. Etc.

But anyway, awesome work, and I look forward to the final stretches.

Jason