From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-0.3 required=5.0 tests=BAYES_00, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 X-Google-Thread: a07f3367d7,cae92f92d6a1d4b1 X-Google-Attributes: gida07f3367d7,public,usenet X-Google-NewGroupId: yes X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news4.google.com!feeder1.cambriumusenet.nl!feed.tweaknews.nl!194.134.4.91.MISMATCH!news2.euro.net!newsfeed.freenet.ag!news.netcologne.de!ramfeed1.netcologne.de!newsfeed01.sul.t-online.de!t-online.de!newsfeed.arcor.de!newsspool4.arcor-online.net!news.arcor.de.POSTED!not-for-mail From: "Dmitry A. Kazakov" Subject: Re: Ada.Execution_Time Newsgroups: comp.lang.ada User-Agent: 40tude_Dialog/2.0.15.1 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Reply-To: mailbox@dmitry-kazakov.de Organization: cbb software GmbH References: <1wmsukf0wglz3$.odnzonrpayly.dlg@40tude.net> <6n1c5myuf2uz$.10jl3ln7il3aq.dlg@40tude.net> <8n0mgnFv2sU1@mid.individual.net> <1n3o55xjdjr9t.1u33kb75y2jfl$.dlg@40tude.net> <8n1142Fto2U1@mid.individual.net> <1o5cbm4b1l20d$.19winbma6k5qw.dlg@40tude.net> <8n4mskF7mmU1@mid.individual.net> <8nm30fF7r9U1@mid.individual.net> <1akm5muxu9zni.mu91b7pubqw0$.dlg@40tude.net> <8nrg25FoucU1@mid.individual.net> <2k07hwmh6123.1pgx57welw9of$.dlg@40tude.net> <8nsa76Fj4rU1@mid.individual.net> <1j9i6trxinqtg$.renlw9wdtpsf.dlg@40tude.net> <8nubhsF6e8U1@mid.individual.net> <9ulzg911gy1q.hztezq0qtfee$.dlg@40tude.net> <1oq6oggi7rtzj.4u4yyq6m8r74$.dlg@40tude.net> Date: Tue, 28 Dec 2010 21:03:27 +0100 Message-ID: NNTP-Posting-Date: 28 Dec 2010 21:03:28 CET NNTP-Posting-Host: a4aa77ae.newsspool3.arcor-online.net X-Trace: DXC=IGKW8BeIR03NTD55K=McF=Q^Z^V384Fo<]lROoR18kF[ On Tue, 28 Dec 2010 19:41:40 +0000, (see below) wrote: > On 28/12/2010 16:55, in article 1oq6oggi7rtzj.4u4yyq6m8r74$.dlg@40tude.net, > "Dmitry A. Kazakov" wrote: > >> On Tue, 28 Dec 2010 16:27:18 +0000, (see below) wrote: >> >>> Dmitri reports a modern computer with a timer having a resolution that is >>> thousands or millions of times worse than the CPU's logic clock. >> >> You get me wrong, the timer resolution is OK, it is the system service >> which does not use it properly. In the case of VxWorks the system time is >> incremented from the timer interrupts, e.g. by 1ms. You can set interrupts >> to each 1um spending all processor time handling interrupts. It is an OS >> architecture problem. System time should have been taken from the real time >> counter. > > Surely the interrupt rate does not matter. The KDF9 clock interrupted once > every 2^20 us, but could be read to the nearest 32 us. Can the clock you > speak of not be interrogated between interrupts? Yes, the TSC can be read any time, and, if I correctly remember, each reading will give a new value. PPC RT clock is also reliable. There could be certain issues for multi-core processors, you should take care that the task synchronizing the counter with UTC would not jump from core to core. Alternatively you should synchronize clocks of individual cores. >>> Why has this aspect of computer architecture degenerated so much, I wonder? >>> And why have software people not made more of a push for improvements? >> >> The computer architecture did not degenerate. [...] It is >> usually the standard OS services to blame for not using these clocks. > > I guess the second part of my question stands. 8-) The OSes did not become degenerate it always were. (:-)) -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de