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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5CBEBC46CD2 for ; Tue, 30 Jan 2024 11:51:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:In-Reply-To:References: Message-ID:Date:Subject:CC:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=7wOcouyO9y03XKAZN1VhDAU6QWV/5hZ2hzSCngJUn6U=; b=10Goc2ud48OH3T bF0fLeFuYs2JZwh2xeQW25mDqfrRtfxvxBpOWL39LtALbIPbYhqEl0hPBIaFstPdYv9q4A1HkwZaV ZE2ry41RpNMVGMHI8raUMyqXAGtOvKgjhy6mdvNEWfdihHbrcQB00kOqp1W0TLrBux+HHsxpX/eVy HBu3MKObypWINRhkgqpF2irWaMRPzHSzEIJRZEALBIQObg1S6oYn3UR8zWnzK6Iga525xIK3k3LFR iPx1GuzLwxxIlURzUvgKPCacWJG9NvW5iJXW5IZotuoNsiaEHirE5cgl+bMO/vcPK7LRE8Zsy0gqJ FfuAaQQdziNb1i118lYA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rUmeO-0000000GYsD-1Dfz; Tue, 30 Jan 2024 11:51:36 +0000 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rUmeL-0000000GYpi-0Gu7 for linux-riscv@lists.infradead.org; Tue, 30 Jan 2024 11:51:34 +0000 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with both STARTTLS and AUTH (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-241-VzaTdC0ENPqj-j_pQMBvdA-1; Tue, 30 Jan 2024 11:51:24 +0000 X-MC-Unique: VzaTdC0ENPqj-j_pQMBvdA-1 Received: from AcuMS.Aculab.com (10.202.163.6) by AcuMS.aculab.com (10.202.163.6) with Microsoft SMTP Server (TLS) id 15.0.1497.48; Tue, 30 Jan 2024 11:51:05 +0000 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.048; Tue, 30 Jan 2024 11:51:05 +0000 From: David Laight To: 'Jisheng Zhang' CC: Paul Walmsley , Palmer Dabbelt , Albert Ou , "linux-riscv@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Matteo Croce , kernel test robot Subject: RE: [PATCH 2/3] riscv: optimized memmove Thread-Topic: [PATCH 2/3] riscv: optimized memmove Thread-Index: AQHaUdxjAvIJPrdYsUmtWfJZGIT/drDvKbzwgAMSEICAAAQ2IA== Date: Tue, 30 Jan 2024 11:51:05 +0000 Message-ID: <2391e924440d4e59b7859b8ede8f0954@AcuMS.aculab.com> References: <20240128111013.2450-1-jszhang@kernel.org> <20240128111013.2450-3-jszhang@kernel.org> <59bed43df37b4361a8a1cb31b8582e9b@AcuMS.aculab.com> In-Reply-To: Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240130_035133_418643_F42451E4 X-CRM114-Status: GOOD ( 18.65 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org From: Jisheng Zhang > Sent: 30 January 2024 11:31 > > On Sun, Jan 28, 2024 at 12:47:00PM +0000, David Laight wrote: > > From: Jisheng Zhang > > > Sent: 28 January 2024 11:10 > > > > > > When the destination buffer is before the source one, or when the > > > buffers doesn't overlap, it's safe to use memcpy() instead, which is > > > optimized to use a bigger data size possible. > > > > > ... > > > + * Simply check if the buffer overlaps an call memcpy() in case, > > > + * otherwise do a simple one byte at time backward copy. > > > > I'd at least do a 64bit copy loop if the addresses are aligned. > > > > Thinks a bit more.... > > > > Put the copy 64 bytes code (the body of the memcpy() loop) > > into it an inline function and call it with increasing addresses > > in memcpy() are decrementing addresses in memmove. > > Hi David, > > Besides the 64 bytes copy, there's another optimization in __memcpy: > word-by-word copy even if s and d are not aligned. > So if we make the two optimizd copy as inline functions and call them > in memmove(), we almost duplicate the __memcpy code, so I think > directly calling __memcpy is a bit better. If a forwards copy is valid call memcpy() - which I think you do. If not you can still use the same 'copy 8 register' code that memcpy() uses - just with a decrementing block address. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv