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 X-Spam-Level: X-Spam-Status: No, score=-13.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2F34BC2B9F4 for ; Fri, 18 Jun 2021 01:06:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 071B961245 for ; Fri, 18 Jun 2021 01:06:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233384AbhFRBIN (ORCPT ); Thu, 17 Jun 2021 21:08:13 -0400 Received: from linux.microsoft.com ([13.77.154.182]:36646 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230318AbhFRBIJ (ORCPT ); Thu, 17 Jun 2021 21:08:09 -0400 Received: from mail-pj1-f51.google.com (mail-pj1-f51.google.com [209.85.216.51]) by linux.microsoft.com (Postfix) with ESMTPSA id 0E63420B83FE; Thu, 17 Jun 2021 18:06:00 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 0E63420B83FE DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1623978361; bh=bcgnjvQBfThviAfC+nD0r2UT09RJuWAKCqEqQjpA3Og=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=fUL6DWKLJQUl6vGWhBUXX+k/2dBmtGWCQxF7DjcAdmRLWwjVd1iZZDodMcxjpTpdf 5qheHDrPcxAEBOmU2QOutsCe9ZY+2rSDqtIUnXNkbCXXFHAGCjk7vGLkx6r1krTRrK v9LKbFrGUrExxaaqW8kNvsOShTkFnuIj9ewAOX9c= Received: by mail-pj1-f51.google.com with SMTP id o10-20020a17090aac0ab029016e92770073so4881643pjq.5; Thu, 17 Jun 2021 18:06:00 -0700 (PDT) X-Gm-Message-State: AOAM531TmHof7tRwKrRpZFLHYzy8VRM76ErnQEBG8d9NPNfSK6rMVIL4 AyFaQhUTS4gvgRUxSgLuP7IUBouhObHkazrv8hE= X-Google-Smtp-Source: ABdhPJy1CyLirX67m04udv8UHON+e5LssQwZjwMZGuMURb8bRjcpQvLKYFf0zMAVsCblD14Q5nNYc/2Dk/zxdAQjUN4= X-Received: by 2002:a17:90a:650b:: with SMTP id i11mr8254024pjj.39.1623978360544; Thu, 17 Jun 2021 18:06:00 -0700 (PDT) MIME-Version: 1.0 References: <20210615023812.50885-1-mcroce@linux.microsoft.com> <20210615023812.50885-2-mcroce@linux.microsoft.com> In-Reply-To: From: Matteo Croce Date: Fri, 18 Jun 2021 03:05:24 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/3] riscv: optimized memcpy To: David Laight Cc: Guo Ren , linux-riscv , Linux Kernel Mailing List , linux-arch , Paul Walmsley , Palmer Dabbelt , Albert Ou , Atish Patra , Emil Renner Berthing , Akira Tsukamoto , Drew Fustini , Bin Meng Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 18, 2021 at 2:32 AM Matteo Croce wrote: > > On Thu, Jun 17, 2021 at 11:48 PM Matteo Croce > wrote: > > > > On Thu, Jun 17, 2021 at 11:30 PM David Laight wrote: > > > > > > From: Matteo Croce > > > > Sent: 16 June 2021 19:52 > > > > To: Guo Ren > > > > > > > > On Wed, Jun 16, 2021 at 1:46 PM Guo Ren wrote: > > > > > > > > > > Hi Matteo, > > > > > > > > > > Have you tried Glibc generic implementation code? > > > > > ref: https://lore.kernel.org/linux-arch/20190629053641.3iBfk9- > > > > I_D29cDp9yJnIdIg7oMtHNZlDmhLQPTumhEc@z/#t > > > > > > > > > > If Glibc codes have the same performance in your hardware, then you > > > > > could give a generic implementation first. > > > > > > Isn't that a byte copy loop - the performance of that ought to be terrible. > > > ... > > > > > > > I had a look, it seems that it's a C unrolled version with the > > > > 'register' keyword. > > > > The same one was already merged in nios2: > > > > https://elixir.bootlin.com/linux/latest/source/arch/nios2/lib/memcpy.c#L68 > > > > > > I know a lot about the nios2 instruction timings. > > > (I've looked at code execution in the fpga's intel 'logic analiser.) > > > It is a very simple 4-clock pipeline cpu with a 2-clock delay > > > before a value read from 'tightly coupled memory' (aka cache) > > > can be used in another instruction. > > > There is also a subtle pipeline stall if a read follows a write > > > to the same memory block because the write is executed one > > > clock later - and would collide with the read. > > > Since it only ever executes one instruction per clock loop > > > unrolling does help - since you never get the loop control 'for free'. > > > OTOH you don't need to use that many registers. > > > But an unrolled loop should approach 2 bytes/clock (32bit cpu). > > > > > > > I copied _wordcopy_fwd_aligned() from Glibc, and I have a very similar > > > > result of the other versions: > > > > > > > > [ 563.359126] Strings selftest: memcpy(src+7, dst+7): 257 Mb/s > > > > > > What clock speed is that running at? > > > It seems very slow for a 64bit cpu (that isn't an fpga soft-cpu). > > > > > > While the small riscv cpu might be similar to the nios2 (and mips > > > for that matter), there are also bigger/faster cpu. > > > I'm sure these can execute multiple instructions/clock > > > and possible even read and write at the same time. > > > Unless they also support significant instruction re-ordering > > > the trivial copy loops are going to be slow on such cpu. > > > > > > > It's running at 1 GHz. > > > > I get 257 Mb/s with a memcpy, a bit more with a memset, > > but I get 1200 Mb/s with a cyle which just reads memory with 64 bit addressing. > > > > Err, I forget a mlock() before accessing the memory in userspace. > > The real speed here is: > > 8 bit read: 155.42 Mb/s > 64 bit read: 277.29 Mb/s > 8 bit write: 138.57 Mb/s > 64 bit write: 239.21 Mb/s > Anyway, thanks for the info on nio2 timings. If you think that an unrolled loop would help, we can achieve the same in C. I think we could code something similar to a Duff device (or with jump labels) to unroll the loop but at the same time doing efficient small copies. Regards, -- per aspera ad upstream 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 X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6F06C2B9F4 for ; Fri, 18 Jun 2021 01:06:25 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 83116600D1 for ; Fri, 18 Jun 2021 01:06:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 83116600D1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org 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:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=YnF+KglcKF3Dl8RGivgu1NKVcXysubZiyUNMZaRrrwI=; b=nL0xtiWZSnFwa4 SDsP/G5tLXBTdSf5oyyrXu3Xczw3VQywLi56JWfmcaM1MtZsEIzpDCnfHeROz2iC/YMjHUuKJyKYJ TPid0IVFyV7hcN+Jbf1WNj9LSz5Oz5UHIsChpkvohNEaqe48KOueNjRtBs/nUN9U3wAnse4M9uWRX PwF01zBRU8nEgyM7LVuhvqJGujwrIIh5FJLQfUFL0jnygCv/9YnFdAjdL9uOyB3D52UEDec1eUCJZ 011YP2v6kw84OgQwOV7GER7KFKIIPLpdrFfqVCmGnRjHBfPRj2OIywHog6CeXBgWClFVhgyUGR62z KXIqfrp0eflTncOvDetg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lu2xV-00CFo7-B9; Fri, 18 Jun 2021 01:06:09 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lu2xS-00CFnM-To for linux-riscv@lists.infradead.org; Fri, 18 Jun 2021 01:06:08 +0000 Received: from mail-pj1-f54.google.com (mail-pj1-f54.google.com [209.85.216.54]) by linux.microsoft.com (Postfix) with ESMTPSA id 0281920B83F2 for ; Thu, 17 Jun 2021 18:06:00 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 0281920B83F2 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1623978361; bh=bcgnjvQBfThviAfC+nD0r2UT09RJuWAKCqEqQjpA3Og=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=fUL6DWKLJQUl6vGWhBUXX+k/2dBmtGWCQxF7DjcAdmRLWwjVd1iZZDodMcxjpTpdf 5qheHDrPcxAEBOmU2QOutsCe9ZY+2rSDqtIUnXNkbCXXFHAGCjk7vGLkx6r1krTRrK v9LKbFrGUrExxaaqW8kNvsOShTkFnuIj9ewAOX9c= Received: by mail-pj1-f54.google.com with SMTP id x21-20020a17090aa395b029016e25313bfcso4896903pjp.2 for ; Thu, 17 Jun 2021 18:06:00 -0700 (PDT) X-Gm-Message-State: AOAM530KffmQ0V2IgYmMYzaAq+OHqvoLeoBTrx+7QY9/ydQmxufShKom /aVjDOpsH21Co2s2YCtl3HXdmzxBtaZTpxdDxoE= X-Google-Smtp-Source: ABdhPJy1CyLirX67m04udv8UHON+e5LssQwZjwMZGuMURb8bRjcpQvLKYFf0zMAVsCblD14Q5nNYc/2Dk/zxdAQjUN4= X-Received: by 2002:a17:90a:650b:: with SMTP id i11mr8254024pjj.39.1623978360544; Thu, 17 Jun 2021 18:06:00 -0700 (PDT) MIME-Version: 1.0 References: <20210615023812.50885-1-mcroce@linux.microsoft.com> <20210615023812.50885-2-mcroce@linux.microsoft.com> In-Reply-To: From: Matteo Croce Date: Fri, 18 Jun 2021 03:05:24 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/3] riscv: optimized memcpy To: David Laight Cc: Guo Ren , linux-riscv , Linux Kernel Mailing List , linux-arch , Paul Walmsley , Palmer Dabbelt , Albert Ou , Atish Patra , Emil Renner Berthing , Akira Tsukamoto , Drew Fustini , Bin Meng X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210617_180607_049758_69DA174D X-CRM114-Status: GOOD ( 40.86 ) 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 On Fri, Jun 18, 2021 at 2:32 AM Matteo Croce wrote: > > On Thu, Jun 17, 2021 at 11:48 PM Matteo Croce > wrote: > > > > On Thu, Jun 17, 2021 at 11:30 PM David Laight wrote: > > > > > > From: Matteo Croce > > > > Sent: 16 June 2021 19:52 > > > > To: Guo Ren > > > > > > > > On Wed, Jun 16, 2021 at 1:46 PM Guo Ren wrote: > > > > > > > > > > Hi Matteo, > > > > > > > > > > Have you tried Glibc generic implementation code? > > > > > ref: https://lore.kernel.org/linux-arch/20190629053641.3iBfk9- > > > > I_D29cDp9yJnIdIg7oMtHNZlDmhLQPTumhEc@z/#t > > > > > > > > > > If Glibc codes have the same performance in your hardware, then you > > > > > could give a generic implementation first. > > > > > > Isn't that a byte copy loop - the performance of that ought to be terrible. > > > ... > > > > > > > I had a look, it seems that it's a C unrolled version with the > > > > 'register' keyword. > > > > The same one was already merged in nios2: > > > > https://elixir.bootlin.com/linux/latest/source/arch/nios2/lib/memcpy.c#L68 > > > > > > I know a lot about the nios2 instruction timings. > > > (I've looked at code execution in the fpga's intel 'logic analiser.) > > > It is a very simple 4-clock pipeline cpu with a 2-clock delay > > > before a value read from 'tightly coupled memory' (aka cache) > > > can be used in another instruction. > > > There is also a subtle pipeline stall if a read follows a write > > > to the same memory block because the write is executed one > > > clock later - and would collide with the read. > > > Since it only ever executes one instruction per clock loop > > > unrolling does help - since you never get the loop control 'for free'. > > > OTOH you don't need to use that many registers. > > > But an unrolled loop should approach 2 bytes/clock (32bit cpu). > > > > > > > I copied _wordcopy_fwd_aligned() from Glibc, and I have a very similar > > > > result of the other versions: > > > > > > > > [ 563.359126] Strings selftest: memcpy(src+7, dst+7): 257 Mb/s > > > > > > What clock speed is that running at? > > > It seems very slow for a 64bit cpu (that isn't an fpga soft-cpu). > > > > > > While the small riscv cpu might be similar to the nios2 (and mips > > > for that matter), there are also bigger/faster cpu. > > > I'm sure these can execute multiple instructions/clock > > > and possible even read and write at the same time. > > > Unless they also support significant instruction re-ordering > > > the trivial copy loops are going to be slow on such cpu. > > > > > > > It's running at 1 GHz. > > > > I get 257 Mb/s with a memcpy, a bit more with a memset, > > but I get 1200 Mb/s with a cyle which just reads memory with 64 bit addressing. > > > > Err, I forget a mlock() before accessing the memory in userspace. > > The real speed here is: > > 8 bit read: 155.42 Mb/s > 64 bit read: 277.29 Mb/s > 8 bit write: 138.57 Mb/s > 64 bit write: 239.21 Mb/s > Anyway, thanks for the info on nio2 timings. If you think that an unrolled loop would help, we can achieve the same in C. I think we could code something similar to a Duff device (or with jump labels) to unroll the loop but at the same time doing efficient small copies. Regards, -- per aspera ad upstream _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv