From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.2 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (server1.sourceware.org [209.132.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id 475ED1F462 for ; Wed, 22 May 2019 12:38:50 +0000 (UTC) DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:subject:to:references:cc:from:message-id:date :mime-version:in-reply-to:content-type :content-transfer-encoding; q=dns; s=default; b=n317oCYdYGStpmcT 33y5ie5j3OCB/ss9EzunOkaYiKOnfCv7VkdlwWxCTSQA056/AdU1AUIZIjHyMf2X wCkn8xewPf8z8P9Ttth4NNYqpYr2SkK9NSkiR0MWm8u+hRDvAj4i5dXYx4xUgCi1 PgK0h6glY+GXeOs/xpt8lbggnQo= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:subject:to:references:cc:from:message-id:date :mime-version:in-reply-to:content-type :content-transfer-encoding; s=default; bh=NUXuUdCi7tAN+a0DJD+sBu VADoI=; b=AT6G3d+Jsyia0dO6Gysq3Hp8wun5IFH1fD9YVt4LYy4e2ckaz5eDEv P8bSikj8nUfxr5qZxv4vbx8jQ2ci4axLLPVhZsq++4CkZQ3PIWm5brXpZDusOucJ 3LH/qnhxj/QkOljzQaXBKP0b4JbZ8WcwQ0yfGdDvhwH1EhDbr7AmQ= Received: (qmail 86337 invoked by alias); 22 May 2019 12:38:47 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 86328 invoked by uid 89); 22 May 2019 12:38:47 -0000 Authentication-Results: sourceware.org; auth=none X-HELO: forward106j.mail.yandex.net DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bell-sw.com; s=mail; t=1558528722; bh=Vtx5G3sVigQ81NtqYSVOZSEGDSYdo+DRLG0jvkLnvbU=; h=In-Reply-To:From:Cc:Date:References:To:Subject:Message-ID; b=Q/mUHLhxVIuts9OviFLMuNvYsqbmZZDnCyTgiYxyQNu7/VjPOfkwSEkjhjKwTfkp/ iFUal9+Xk3K4mwT+eVtANwFrYezzq4MruxEakJqfWA99xf+daxzpLHKdOqg8K5aY+c F7w/7oKqCYvLNZ7TzOUjdwMKy6kUEuEyps7orka8= Authentication-Results: mxback19g.mail.yandex.net; dkim=pass header.i=@bell-sw.com Subject: Re: [PATCH] Improve string benchtest timing To: Siddhesh Poyarekar , Wilco Dijkstra , Adhemerval Zanella , "libc-alpha@sourceware.org" References: <3acd7a7f-c06a-6679-d526-e758d9ff30ab@gotplt.org> <11d4661e-914d-237b-c2db-c9ef4739460d@gotplt.org> Cc: nd From: Anton Youdkevitch Message-ID: <5CE542D2.5010902@bell-sw.com> Date: Wed, 22 May 2019 15:38:42 +0300 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 MIME-Version: 1.0 In-Reply-To: <11d4661e-914d-237b-c2db-c9ef4739460d@gotplt.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Siddhesh, On 22.5.2019 14:27 , Siddhesh Poyarekar wrote: > On 22/05/19 4:41 PM, Wilco Dijkstra wrote: >> Well if I force the copies to be mutually unaligned, there is only about 1% difference >> for a few of the memcpy implementations compared to them being always aligned >> The others show identical performance whether aligned or not. This is not too >> surprising since the test is basically waiting for DRAM most of the time. > > That's a good point. Is that the case for thunderx as well? IIRC they > perform particularly badly with misaligned code but I don't know if > they're bad enough to be significant in the face of DRAM waits. They were. The difference was up to 50% in some cases. But this is the data for bench-memcpy. Reports for bench-memcpy-walk and bench-memcpy-random do not have alignment info in them. So, unaligned accesses can be much slower that aligned ones. Or, at least, this is how the benchmarks measure them. We already know that the results are not very stable, though. P.S. To be precise I'm speaking about TX2 here. -- Thanks, Anton