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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">I can appreciate it wouldn’t be suitable in the general case for time, but for our use case of timing intervals for performance analysis
the monotonic nature is less important.<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Lukas Larsson [mailto:lukas.larsson@erlang-solutions.com]
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<b>Sent:</b> 29 January 2016 14:38<br>
<b>To:</b> Rob A'Court <rob@cloudhouse.com><br>
<b>Cc:</b> erlang-questions@erlang.org<br>
<b>Subject:</b> Re: [erlang-questions] Time Granularity on Windows<o:p></o:p></span></p>
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<p class="MsoNormal">The problem with QPC is that it is not monotonic. From <a href="https://msdn.microsoft.com/en-us/library/dn553408.aspx">https://msdn.microsoft.com/en-us/library/dn553408.aspx</a>.<o:p></o:p></p>
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<p class="MsoNormal">"Can the performance counter be used to order events in time?<o:p></o:p></p>
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<p class="MsoNormal">Yes. However, when comparing performance counter results that are acquired from different threads, values that differ by ± 1 tick have an ambiguous ordering as if they had an identical time stamp."<o:p></o:p></p>
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<p class="MsoNormal">If it wasn't for that small caveat we would have used it.<o:p></o:p></p>
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<p class="MsoNormal">Lukas<o:p></o:p></p>
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<p class="MsoNormal">On Fri, Jan 29, 2016 at 2:32 PM, Rob A'Court <<a href="mailto:rob@cloudhouse.com" target="_blank">rob@cloudhouse.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Ok, fine. Thank you!</span><o:p></o:p></p>
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<pre><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">We’ve done a bit more research and it looks like it is possible to get better granularity on Windows, but only by making a windows kernel call:</span><o:p></o:p></pre>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><a href="http://erlang.org/pipermail/erlang-questions/2011-May/058940.html" target="_blank">http://erlang.org/pipermail/erlang-questions/2011-May/058940.html</a></span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Lukas
Larsson [mailto:<a href="mailto:lukas@erlang.org" target="_blank">lukas@erlang.org</a>]
<br>
<b>Sent:</b> 29 January 2016 10:33<br>
<b>To:</b> Rob A'Court <<a href="mailto:rob@cloudhouse.com" target="_blank">rob@cloudhouse.com</a>><br>
<b>Cc:</b> <a href="mailto:erlang-questions@erlang.org" target="_blank">erlang-questions@erlang.org</a><br>
<b>Subject:</b> Re: [erlang-questions] Time Granularity on Windows</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hello,<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">On Fri, Jan 29, 2016 at 11:17 AM, Rob A'Court <<a href="mailto:rob@cloudhouse.com" target="_blank">rob@cloudhouse.com</a>> wrote:<o:p></o:p></p>
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<o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:"Arial",sans-serif;color:#222222">Is this a problem with something I am doing or with the granularity of the windows system clock? </span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">It is a problem with the granularity of the monotonic time source on Windows.<o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:"Arial",sans-serif;color:#222222">Is there another approach I could take to get accurate (~microsecond granularity) timestamps on windows and linux?</span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:"Arial",sans-serif;color:#222222"> </span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Maybe try os:timestamp on windows? I can't remember what it falls back onto, but as it does not have any monoticity guarantees it may give better values.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Lukas<o:p></o:p></p>
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