From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 21ABBEC873D for ; Thu, 7 Sep 2023 16:27:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229517AbjIGQ1G (ORCPT ); Thu, 7 Sep 2023 12:27:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38544 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236774AbjIGQ0E (ORCPT ); Thu, 7 Sep 2023 12:26:04 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DBC2E61B5 for ; Thu, 7 Sep 2023 09:22:07 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F35CC433BA; Thu, 7 Sep 2023 09:47:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1694080080; bh=ioGfmHzP2GjyiqSrlbgIeRZSwKKtv0WFrj6DT7aSlks=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mLg+V3E9qaY9ombLvd77WkJ4/u93T3ZxXYPB4JdXuB2oOzxLDlNH9me5cEiN8IEDD hgdcdLXevKfMKThzJM3m0rYD9+Ykd5RhvO6XkbmVQ3PBaJKr+e5VHPHJVgj8FSMtqh seudiFFp8FoptyZa7+75TrW0fR3Kqzi4Ddu8I1Pv3m8x4haMO+ce/alSOsvuWix0vn mlfkBLMWtqfw88o/g6UpO5As/0Hq8PDu2TIysni9GCEfqpMNA7Pz7fB9XBNw3RoHgl 6XBIZDE/7Ok4eCoxfG8mDSQELRd/uBlK54ZtotPlOlmfTPFBkJiRSwLAkPjdhKXxBt IpVH2dLHk7Dpg== Date: Thu, 7 Sep 2023 10:47:55 +0100 From: Conor Dooley To: Charlie Jenkins Cc: Palmer Dabbelt , Samuel Holland , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Paul Walmsley , Albert Ou Subject: Re: [PATCH v2 3/5] riscv: Vector checksum header Message-ID: <20230907-c23868a1016a17299a470120@fedora> References: <20230905-optimize_checksum-v2-0-ccd658db743b@rivosinc.com> <20230905-optimize_checksum-v2-3-ccd658db743b@rivosinc.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="yWEbZ60EvanaedV2" Content-Disposition: inline In-Reply-To: <20230905-optimize_checksum-v2-3-ccd658db743b@rivosinc.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --yWEbZ60EvanaedV2 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Sep 05, 2023 at 09:46:52PM -0700, Charlie Jenkins wrote: > Vector code is written in assembly rather than using the GCC vector > instrinsics because they did not provide optimal code. Vector > instrinsic types are still used so the inline assembly can > appropriately select vector registers. However, this code cannot be > merged yet because it is currently not possible to use vector > instrinsics in the kernel because vector support needs to be directly > enabled by assembly. >=20 > Signed-off-by: Charlie Jenkins > --- > arch/riscv/include/asm/checksum.h | 87 +++++++++++++++++++++++++++++++++= ++++++ > 1 file changed, 87 insertions(+) >=20 > diff --git a/arch/riscv/include/asm/checksum.h b/arch/riscv/include/asm/c= hecksum.h > index 3f9d5a202e95..1d6c23cd1221 100644 > --- a/arch/riscv/include/asm/checksum.h > +++ b/arch/riscv/include/asm/checksum.h > @@ -10,6 +10,10 @@ > #include > #include > =20 > +#ifdef CONFIG_RISCV_ISA_V > +#include > +#endif > + > #ifdef CONFIG_32BIT > typedef unsigned int csum_t; > #else > @@ -43,6 +47,89 @@ static inline __sum16 csum_fold(__wsum sum) > */ > static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl) > { > +#ifdef CONFIG_RISCV_ISA_V > + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE)) { > + /* > + * Vector is likely available when the kernel is compiled with > + * vector support, so nop when vector is available and jump when > + * vector is not available. > + */ > + asm_volatile_goto(ALTERNATIVE("j %l[no_vector]", "nop", 0, > + RISCV_ISA_EXT_v, 1) > + : > + : > + : > + : no_vector); > + } else { > + if (!__riscv_isa_extension_available(NULL, RISCV_ISA_EXT_v)) > + goto no_vector; > + } Silly question maybe, but is this complexity required? If you were to go and do if (!has_vector()) goto no_vector is there any meaningful difference difference in performance? > + > + vuint64m1_t prev_buffer; > + vuint32m1_t curr_buffer; > + unsigned int vl; > +#ifdef CONFIG_32_BIT > + csum_t high_result, low_result; > + > + riscv_v_enable(); > + asm(".option push \n\ > + .option arch, +v \n\ > + vsetivli x0, 1, e64, ta, ma \n\ > + vmv.v.i %[prev_buffer], 0 \n\ > + 1: \n\ > + vsetvli %[vl], %[ihl], e32, m1, ta, ma \n\ > + vle32.v %[curr_buffer], (%[iph]) \n\ > + vwredsumu.vs %[prev_buffer], %[curr_buffer], %[prev_buffer] \n\ > + sub %[ihl], %[ihl], %[vl] \n\ > + slli %[vl], %[vl], 2 \n\ Also, could you please try to align the operands for asm stuff? It makes quite a difference to readability. Thanks, Conor. > + add %[iph], %[vl], %[iph] \n\ > + # If not all of iph could fit into vector reg, do another sum \n\ > + bne %[ihl], zero, 1b \n\ > + vsetivli x0, 1, e64, m1, ta, ma \n\ > + vmv.x.s %[low_result], %[prev_buffer] \n\ > + addi %[vl], x0, 32 \n\ > + vsrl.vx %[prev_buffer], %[prev_buffer], %[vl] \n\ > + vmv.x.s %[high_result], %[prev_buffer] \n\ > + .option pop" > + : [vl] "=3D&r" (vl), [prev_buffer] "=3D&vd" (prev_buffer), > + [curr_buffer] "=3D&vd" (curr_buffer), > + [high_result] "=3D&r" (high_result), > + [low_result] "=3D&r" (low_result) > + : [iph] "r" (iph), [ihl] "r" (ihl)); > + riscv_v_disable(); > + > + high_result +=3D low_result; > + high_result +=3D high_result < low_result; > +#else // !CONFIG_32_BIT > + csum_t result; > + > + riscv_v_enable(); > + asm(".option push \n\ > + .option arch, +v \n\ > + vsetivli x0, 1, e64, ta, ma \n\ > + vmv.v.i %[prev_buffer], 0 \n\ > + 1: \n\ > + # Setup 32-bit sum of iph \n\ > + vsetvli %[vl], %[ihl], e32, m1, ta, ma \n\ > + vle32.v %[curr_buffer], (%[iph]) \n\ > + # Sum each 32-bit segment of iph that can fit into a vector reg \n\ > + vwredsumu.vs %[prev_buffer], %[curr_buffer], %[prev_buffer] \n\ > + subw %[ihl], %[ihl], %[vl] \n\ > + slli %[vl], %[vl], 2 \n\ > + addw %[iph], %[vl], %[iph] \n\ > + # If not all of iph could fit into vector reg, do another sum \n\ > + bne %[ihl], zero, 1b \n\ > + vsetvli x0, x0, e64, m1, ta, ma \n\ > + vmv.x.s %[result], %[prev_buffer] \n\ > + .option pop" > + : [vl] "=3D&r" (vl), [prev_buffer] "=3D&vd" (prev_buffer), > + [curr_buffer] "=3D&vd" (curr_buffer), [result] "=3D&r" (result) > + : [iph] "r" (iph), [ihl] "r" (ihl)); > + riscv_v_disable(); > +#endif // !CONFIG_32_BIT > +no_vector: > +#endif // !CONFIG_RISCV_ISA_V > + > csum_t csum =3D 0; > int pos =3D 0; > =20 >=20 > --=20 > 2.42.0 >=20 --yWEbZ60EvanaedV2 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEARYKAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCZPmcSwAKCRB4tDGHoIJi 0vRZAP0ZzhCs5vuiNpTlPt5BMdF0YNy9cfs2lZWKaag7QXHn7wEA4ERG47/qqF3a avJy0xAtqa0LYQnJFnR6V2NQdmXA0gg= =XGt0 -----END PGP SIGNATURE----- --yWEbZ60EvanaedV2--