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: 103376,cae92f92d6a1d4b1 X-Google-NewGroupId: yes X-Google-Attributes: gida07f3367d7,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news2.google.com!border1.nntp.dca.giganews.com!border4.nntp.dca.giganews.com!border2.nntp.dca.giganews.com!nntp.giganews.com!feedme.ziplink.net!news.swapon.de!newsfeed.straub-nv.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> Date: Tue, 28 Dec 2010 17:55:42 +0100 Message-ID: <1oq6oggi7rtzj.4u4yyq6m8r74$.dlg@40tude.net> NNTP-Posting-Date: 28 Dec 2010 17:55:42 CET NNTP-Posting-Host: d4fe5d25.newsspool2.arcor-online.net X-Trace: DXC=3fPhM@U;ZBZaAeROF2PWMQA9EHlD;3YcR4Fo<]lROoRQ8kF 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. > 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. Modern processor and motherboard have multiple time sources 3-4. Some of them have a very high resolution and reliable, e.g. keep on counting in the sleep mode etc. It is usually the standard OS services to blame for not using these clocks. Practically in any OS there is a backdoor to get a decent real-time clock. Then the journey begins. You need to synchronize readings from that clock (usually a 64-bit counter) with the system time (of miserable accuracy) in order to get a decent UTC stamp. This is doable using some statistical method, depending on your needs (monotonic, or not, etc). Shame that the OS does not do this. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de