From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-x534.google.com (mail-pg1-x534.google.com [IPv6:2607:f8b0:4864:20::534]) by sourceware.org (Postfix) with ESMTPS id DA5D03972835 for ; Mon, 28 Jun 2021 11:55:35 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org DA5D03972835 Received: by mail-pg1-x534.google.com with SMTP id d12so15252178pgd.9 for ; Mon, 28 Jun 2021 04:55:35 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=7o8LiqI9ujve/fqzd6cPEeeUcFtpK7EjZe5rM+W6XaA=; b=VELNgiZR24bNZzoGpyg5TirTKPdMkM3X30rMsb9+1mxzt0EHuarq8tHc45Ek+gSYLC S+Xou2E2ngW5cpHauSUvjeLAKZN7d2JWGK1FUmkk+2HzlODwdI5eiKpxigB5FPR7Ehv9 A7wjQBo6PsSJM7/iFDpFOAYuHno2siqNMw2UhIeJOM80vl7PlQRgdPVQ/JFAJ1dJe9s/ RJGbuh2RWzvimojAauGFUsc2YKk5oDWmwVtr6mCcUZ1G2N7546KfsVS3VqCAhOJaNufV MDh3ycywmeLMfIrMqFaSNPUiUMRSlUIYJRxv1jcqCR1v16nsbfkrg4u6aPofZhJAdD70 CPVQ== X-Gm-Message-State: AOAM530HqP6DUG4Nfo3lCurHAheAMSVXuZIORPC9hikmlWk2Dy76/GUl RGNf1MgNyXBoLyNQj8R9/5q7A4PNbPOzJA== X-Google-Smtp-Source: ABdhPJx3ir+tp2/NgISySiOnr98ZItvRqaVlAnlNBcozU72oV+P2ehu28vSEY2p+G2MrDhxcAt/Weg== X-Received: by 2002:a62:8fc8:0:b029:2ec:9b7a:f59e with SMTP id n191-20020a628fc80000b02902ec9b7af59emr24534830pfd.39.1624881334810; Mon, 28 Jun 2021 04:55:34 -0700 (PDT) Received: from [192.168.1.108] ([177.194.59.218]) by smtp.gmail.com with ESMTPSA id n14sm14463639pjo.15.2021.06.28.04.55.33 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 28 Jun 2021 04:55:34 -0700 (PDT) Subject: Re: [PATCH] AArch64: Add hp-timing.h To: libc-alpha@sourceware.org References: <87pmw6uw73.fsf@oldenburg.str.redhat.com> <87h7hiuu3d.fsf@oldenburg.str.redhat.com> <20210628114927.GM13058@arm.com> From: Adhemerval Zanella Message-ID: Date: Mon, 28 Jun 2021 08:55:31 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210628114927.GM13058@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-6.3 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 28 Jun 2021 11:55:37 -0000 On 28/06/2021 08:49, Szabolcs Nagy via Libc-alpha wrote: > The 06/28/2021 13:06, Florian Weimer wrote: >> * Wilco Dijkstra: >>> Hi Florian, >>>> Is the MSR called cntcvt_el0 or cntvct_el0? >>> >>> cntvct_el0 - it's just a random combination of characters! >> >> Okay, then please fix the other occurence that is a typo. >> >>>> I'm clearly missing something: If this is broken on some kernels, how is >>>> this disabled? >>> >>> It's not enabled just to be extremely conservative - however I don't >>> believe this is an issue in practice since it works fine even on the >>> first AArch64 boards and servers. >> >> I meant: How is this disabled in glibc on older kernels? Or is this >> code just dormant as of now? > > iirc linux devs asked that it is only used in vdso so > that it is under the kernel's control in case there > are implementation issues (vdso is easy to disable > and on some system it got disabled for timer reasons). > > is hp-timing.h for some internal benchmarks only? > > if no, then i think we should get the opinion of > linux maintainers before we use this in glibc. > The patch sets HP_TIMING_INLINE to 0, so it is only used on benchmarks.