From nobody Mon Oct 11 07:53:31 2021 X-Original-To: freebsd-hackers@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id AC87517F1951 for ; Mon, 11 Oct 2021 07:53:34 +0000 (UTC) (envelope-from sebastian.huber@embedded-brains.de) Received: from dedi548.your-server.de (dedi548.your-server.de [85.10.215.148]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4HSWJF6jBdz3Gcy for ; Mon, 11 Oct 2021 07:53:33 +0000 (UTC) (envelope-from sebastian.huber@embedded-brains.de) Received: from sslproxy02.your-server.de ([78.47.166.47]) by dedi548.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92.3) (envelope-from ) id 1mZq7o-000AkD-PV for freebsd-hackers@freebsd.org; Mon, 11 Oct 2021 09:53:32 +0200 Received: from [82.100.198.138] (helo=mail.embedded-brains.de) by sslproxy02.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1mZq7o-000FSV-Mq for freebsd-hackers@freebsd.org; Mon, 11 Oct 2021 09:53:32 +0200 Received: from localhost (localhost [127.0.0.1]) by mail.embedded-brains.de (Postfix) with ESMTP id 614DA48006A for ; Mon, 11 Oct 2021 09:53:32 +0200 (CEST) Received: from mail.embedded-brains.de ([127.0.0.1]) by localhost (zimbra.eb.localhost [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id e5OBzhuB5i0T for ; Mon, 11 Oct 2021 09:53:32 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by mail.embedded-brains.de (Postfix) with ESMTP id 208A74800E2 for ; Mon, 11 Oct 2021 09:53:32 +0200 (CEST) X-Virus-Scanned: amavisd-new at zimbra.eb.localhost Received: from mail.embedded-brains.de ([127.0.0.1]) by localhost (zimbra.eb.localhost [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id uCMGOn6UxrEA for ; Mon, 11 Oct 2021 09:53:32 +0200 (CEST) Received: from [10.10.171.10] (unknown [10.10.171.10]) by mail.embedded-brains.de (Postfix) with ESMTPSA id 0127648006A for ; Mon, 11 Oct 2021 09:53:31 +0200 (CEST) To: FreeBSD Hackers From: Sebastian Huber Subject: Large timecounter delta handling Message-ID: <5318327d-d247-bb73-81d9-967c4ae18d32@embedded-brains.de> Date: Mon, 11 Oct 2021 09:53:31 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 List-Id: Technical discussions relating to FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-hackers List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-hackers@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-Authenticated-Sender: smtp-embedded@poldinet.de X-Virus-Scanned: Clear (ClamAV 0.103.3/26318/Sun Oct 10 10:18:47 2021) X-Rspamd-Queue-Id: 4HSWJF6jBdz3Gcy X-Spamd-Bar: - Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=pass (mx1.freebsd.org: domain of sebastian.huber@embedded-brains.de designates 85.10.215.148 as permitted sender) smtp.mailfrom=sebastian.huber@embedded-brains.de X-Spamd-Result: default: False [-1.28 / 15.00]; RCVD_TLS_LAST(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; R_SPF_ALLOW(-0.20)[+ip4:85.10.215.148]; MIME_GOOD(-0.10)[text/plain]; PREVIOUSLY_DELIVERED(0.00)[freebsd-hackers@freebsd.org]; ARC_NA(0.00)[]; NEURAL_SPAM_MEDIUM(0.99)[0.990]; RCPT_COUNT_ONE(0.00)[1]; NEURAL_HAM_LONG(-0.97)[-0.969]; DMARC_NA(0.00)[embedded-brains.de]; TO_DN_ALL(0.00)[]; NEURAL_HAM_SHORT(-1.00)[-1.000]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:24940, ipnet:85.10.192.0/18, country:DE]; RCVD_COUNT_SEVEN(0.00)[8]; HAS_X_AS(0.00)[] X-ThisMailContainsUnwantedMimeParts: N Hello, I synchronize currently the port of the FreeBSD timecounters to RTEMS. I=20 have to write test cases for all code we use in RTEMS. In 2020 some code=20 was added to fix integer overflow issues with large time deltas while=20 getting the time from a timehand. https://github.com/freebsd/freebsd-src/commit/6cf2362e2c7e9061611f93a48ec= 654a5b7451d6b#diff-8b8e2f8e41e6a847f14ab08c7d50454c20a4a135f2c2241d91687c= 0832c1d99e If a time delta obtained by tc_delta(th) is greater than or equal to=20 th->th_large_delta, then some extra calculation is carried out. The th->th_large_delta is computed like this scale =3D (uint64_t)1 << 63; scale +=3D (th->th_adjustment / 1024) * 2199; scale /=3D th->th_counter->tc_frequency; th->th_scale =3D scale * 2; th->th_large_delta =3D MIN(((uint64_t)1 << 63) / scale, UINT_MAX); If we ignore the th->th_adjustment (=3D=3D 0), then we have ideally scale =3D 2**64 / f th->th_large_delta =3D MIN( f / 2, UINT_MAX ) Does this mean that we only need the large delta processing if a=20 timehand was not updated for about 0.5s? --=20 embedded brains GmbH Herr Sebastian HUBER Dornierstr. 4 82178 Puchheim Germany email: sebastian.huber@embedded-brains.de phone: +49-89-18 94 741 - 16 fax: +49-89-18 94 741 - 08 Registergericht: Amtsgericht M=C3=BCnchen Registernummer: HRB 157899 Vertretungsberechtigte Gesch=C3=A4ftsf=C3=BChrer: Peter Rasmussen, Thomas= D=C3=B6rfler Unsere Datenschutzerkl=C3=A4rung finden Sie hier: https://embedded-brains.de/datenschutzerklaerung/