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=-4.1 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,RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL,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 9DBF11F619 for ; Tue, 3 Mar 2020 15:23:51 +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:from:message-id:date :mime-version:in-reply-to:content-type :content-transfer-encoding; q=dns; s=default; b=VPsgMyB8DYpcG50w NVqJscrX17jZb2pw95uuefNyrYC85IblSsYF5I1JXuAXUExArpo8swcMeKayItrV V21Dsd+FuJOvgCwPjG6FRKB3h5dz7o1mgJQfdKPwjqrY0n7BjNHSY5XffIAkFYJO 70cJMifRN63dqSxCF2RNf+zvR88= 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:from:message-id:date :mime-version:in-reply-to:content-type :content-transfer-encoding; s=default; bh=CaFLAPVKl++afPLYnbmCqn 7l2Mw=; b=Y9pmaYeyOWoHQu76I0Wk8emeptrEK7forQ6ZiPbetpMkJBAWidewk1 DRICqzx8CtPPAlquSyzWltsOMtmewbWmSgpHNMclBp9gOFKoXZWlNBcg1D/I9aHj FEoDKS7nK+s6hbPF7n+yQdAtArWJ1Qj+SYezguBF1JKdSU08RO5+c= Received: (qmail 20554 invoked by alias); 3 Mar 2020 15:23:48 -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 20546 invoked by uid 89); 3 Mar 2020 15:23:48 -0000 Authentication-Results: sourceware.org; auth=none X-HELO: crocodile.birch.relay.mailchannels.net X-Sender-Id: dreamhost|x-authsender|siddhesh@gotplt.org X-Sender-Id: dreamhost|x-authsender|siddhesh@gotplt.org X-MC-Relay: Neutral X-MailChannels-SenderId: dreamhost|x-authsender|siddhesh@gotplt.org X-MailChannels-Auth-Id: dreamhost X-Troubled-Lyrical: 409818744af1dfc1_1583249024511_762634203 X-MC-Loop-Signature: 1583249024511:233879034 X-MC-Ingress-Time: 1583249024511 DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=gotplt.org; h=subject:to :references:from:message-id:date:mime-version:in-reply-to :content-type:content-transfer-encoding; s=gotplt.org; bh=CaFLAP VKl++afPLYnbmCqn7l2Mw=; b=JrEMIZCP9WfmtpHZ8Zzlwg6r0XK38Aifravgvr NvMYQusHLsO2o5/Gj/HbbSr+wkc7dUFtV3dAK7DAWfHQToSLMm6TM9j0iiFB5COl TXajTNskJEKgwjkUfZQGKRRYE1R8XTrERrRxAbiHtpBumLQlriL97WPzp6Oy7ISI v0OWc= Subject: Re: [PATCH][AArch64] Cleanup memset To: Wilco Dijkstra , 'GNU C Library' References: X-DH-BACKEND: pdx1-sub0-mail-a64 From: Siddhesh Poyarekar Message-ID: Date: Tue, 3 Mar 2020 20:53:18 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-VR-OUT-STATUS: OK X-VR-OUT-SCORE: -100 X-VR-OUT-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedugedruddtiedgjeekucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuggftfghnshhusghstghrihgsvgdpffftgfetoffjqffuvfenuceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmnecujfgurhepuffvfhfhkffffgggjggtgfesthejredttdefjeenucfhrhhomhepufhiugguhhgvshhhucfrohihrghrvghkrghruceoshhiugguhhgvshhhsehgohhtphhlthdrohhrgheqnecukfhppeduvdefrddvhedvrddvtddvrddujedvnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmohguvgepshhmthhppdhhvghloheplgduledvrdduieekrddurdeljegnpdhinhgvthepuddvfedrvdehvddrvddtvddrudejvddprhgvthhurhhnqdhprghthhepufhiugguhhgvshhhucfrohihrghrvghkrghruceoshhiugguhhgvshhhsehgohhtphhlthdrohhrgheqpdhmrghilhhfrhhomhepshhiugguhhgvshhhsehgohhtphhlthdrohhrghdpnhhrtghpthhtohephghilhgtohdrffhijhhkshhtrhgrsegrrhhmrdgtohhm On 03/03/20 20:12, Wilco Dijkstra wrote: > Hi Siddhesh, > >> This looks OK in general, although can you please elaborate on the >> following: >> >> - What cores did you test on to conclude that 160 is a better threshold >> than 256? > > I've mostly done testing on Neoverse N1, Cortex-A72 and Cortex-A53. > (the latter seems to be always faster with DC ZVA disabled, so the threshold > doesn't really matter). I wrote a random memset benchmark similar to the > memcpy one, and performance is unchanged there given there is no change > in the way small cases are handled. OK, please mention this in the commit log. >> - Is the intention to support non-64-byte zva sizes once there is actual >> hardware that implements it and not bother with it for now? I agree >> with the idea if that's the case, just that it would be nice to have >> that documented in the git commit message. > > Yes, otherwise it's hard to test or prove it helps performance after all. We've > had issues with the non-64 ZVA sizes before, so it's best to keep it simple. > > I'm also trying to reduce the amount of code and avoid unnecessary proliferation > of almost identical ifuncs. I think we can remove most of the memset ifuncs, > it seems we need one version without ZVA and a ZVA version for size 64. Sounds like a plan. Thanks, Siddhesh