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

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Message-ID: <070a2aa1-a804-4124-ad89-c43e09dc3ded@csgroup.eu>
Date: Wed, 4 Sep 2024 16:36:15 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: "Jason A. Donenfeld" <Jason@...c4.com>
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

Le 04/09/2024 à 16:16, Jason A. Donenfeld a écrit :
> 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.

You can learn a bit more about cvdso_call in commit ce7d8056e38b 
("powerpc/vdso: Prepare for switching VDSO to generic C implementation.")

About the fixed-r30, you can learn more in commit a88603f4b92e 
("powerpc/vdso: Don't use r30 to avoid breaking Go lang")

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

Thanks, looking forward to getting this series applied.

Christophe