From mboxrd@z Thu Jan 1 00:00:00 1970 From: erik quanstrom Date: Mon, 19 May 2014 12:54:05 -0400 To: quanstro@quanstro.net, 9fans@9fans.net Message-ID: <8af63db4d23375bd89b74baa60c0945f@ladd.quanstro.net> In-Reply-To: <063412cb21a6433d959274d7db87d242@ladd.quanstro.net> References: <73d0faddf32ce1bc1d64f05fd113dece@proxima.alt.za> <063412cb21a6433d959274d7db87d242@ladd.quanstro.net> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Subject: Re: [9fans] syscall 53 Topicbox-Message-UUID: e85318fc-ead8-11e9-9d60-3106f5b1d025 On Mon May 19 12:26:00 EDT 2014, quanstro@quanstro.net wrote: > On Mon May 19 10:04:28 EDT 2014, lucio@proxima.alt.za wrote: > > > i indirectly heard "go needs it", but that is not really a reason > > > i can understand technically. why must it be a system call? > > > > Actually, Go raised an important alert, quite indirectly: when using > > high resolution timers, the issue of opening a device, reading it and > > converting the input value to a binary value can and in this case is > > very expensive. > > > > Curiously, the actual symptom - I cannot remember how it came about - > > was that using the timer leaked file descriptors, or, more likely, > > gave the impression of leaking file descriptors. But the reality is > > that nanosecond accuracy cannot be achieved from reading a device by > > conventional means. > > i think my original question still stands. what is the purpose of timing, > what is the desired accuracy and precision, and is a relative or absolute > time wanted? also, one cannot get close to 1ns precision with a system call. a system call takes a bare minimum of 400-500ns on 386/amd64. - erik