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Peter Anvin" To: Christoph Hellwig CC: Andrew Morton , Catalin Marinas , Will Deacon , Ard Biesheuvel , Huacai Chen , WANG Xuerui , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Herbert Xu , Dan Williams , Chris Mason , David Sterba , Arnd Bergmann , Song Liu , Yu Kuai , Li Nan , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-crypto@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-arch@vger.kernel.org, linux-raid@vger.kernel.org Subject: Re: cleanup the RAID6 P/Q library v3 User-Agent: K-9 Mail for Android In-Reply-To: <20260629122152.GA21344@lst.de> References: <20260518051804.462141-1-hch@lst.de> <20260518141205.c100f76eec5f58e78bbbf7af@linux-foundation.org> <20260519082432.GA14956@lst.de> <7d8efc7c-65e3-49f8-9381-910de7affef2@zytor.com> <20260629122152.GA21344@lst.de> Message-ID: <8684FEC2-AD56-4BDA-874F-1D3D7170F880@zytor.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On June 29, 2026 5:21:52 AM PDT, Christoph Hellwig wrote: >On Fri, Jun 26, 2026 at 05:52:18PM -0700, H=2E Peter Anvin wrote: >> On 2026-05-19 01:24, Christoph Hellwig wrote: >> >=20 >> > raid6: rework registration of optimized algorithms >> >=20 >> > - avx2 instead of avx512 is probably the right thing for no >> > benchmarking, but if it was intentional (it wasn't), that should >> > be document=2E So I'll just switch back to the previous version t= o >> > keep the state of the art >>=20 >> It is unlikely to be the right thing *going forward*, though=2E >>=20 >> The very unfortunate performance inversion is likely model-specific=2E = It is one >> of those things where you largely would have to have a list of quirks := ( > >Note that the default is still to benchmark the implementations=2E >This is just about the case where the user explicitly disabled that >benchmark-based selection=2E > The real issue though is that the benchmarking isn't really helpful, eithe= r=2E=20 It has to do with power across the whole chip, so it perversely enough dep= ends on what *else* is going on=2E=2E=2E