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diff --git a/lib/sasl/doc/src/overload.xml b/lib/sasl/doc/src/overload.xml deleted file mode 100644 index 3a82432647..0000000000 --- a/lib/sasl/doc/src/overload.xml +++ /dev/null @@ -1,151 +0,0 @@ -<?xml version="1.0" encoding="utf-8" ?> -<!DOCTYPE erlref SYSTEM "erlref.dtd"> - -<erlref> - <header> - <copyright> - <year>1996</year><year>2013</year> - <holder>Ericsson AB. All Rights Reserved.</holder> - </copyright> - <legalnotice> - The contents of this file are subject to the Erlang Public License, - Version 1.1, (the "License"); you may not use this file except in - compliance with the License. You should have received a copy of the - Erlang Public License along with this software. If not, it can be - retrieved online at http://www.erlang.org/. - - Software distributed under the License is distributed on an "AS IS" - basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See - the License for the specific language governing rights and limitations - under the License. - - </legalnotice> - - <title>overload</title> - <prepared>Peter Högfeldt</prepared> - <responsible>Peter Högfeldt</responsible> - <docno></docno> - <approved>(Joe Armstrong)</approved> - <checked></checked> - <date>1996-10-29</date> - <rev>A</rev> - <file>overload.sgml</file> - </header> - <module>overload</module> - <modulesummary>An Overload Regulation Process</modulesummary> - <description> - <p><c>overload</c> is a process which indirectly regulates CPU - usage in the system. The idea is that a main application calls - the <c>request/0</c> function before starting a major job, and - proceeds with the job if the return value is positive; otherwise - the job must not be started. - </p> - <p><c>overload</c> is part of the <c>sasl</c> application, and all - configuration parameters are defined there. - </p> - <p>A set of two intensities are maintained, the <c>total intensity</c> and the <c>accept intensity</c>. For that purpose - there are two configuration parameters, the <c>MaxIntensity</c> - and the <c>Weight</c> value (both are measured in 1/second). - </p> - <p>Then total and accept intensities are calculated as - follows. Assume that the time of the current call to - <c>request/0</c> is <c>T(n)</c>, and that the time of the - previous call was <c>T(n-1)</c>. - </p> - <list type="bulleted"> - <item> - <p>The current <c>total intensity</c>, denoted - <c>TI(n)</c>, is calculated according to the formula, - </p> - <p><c>TI(n) = exp(-Weight*(T(n) - T(n-1)) * TI(n-1) + Weight</c>, - </p> - <p>where <c>TI(n-1)</c> is the previous total intensity. - </p> - </item> - <item> - <p>The current <c>accept intensity</c>, denoted - <c>AI(n)</c>, is determined by the formula, - </p> - <p><c>AI(n) = exp(-Weight*(T(n) - T(n-1)) * AI(n-1) + Weight</c>, - </p> - <p>where <c>AI(n-1)</c> is the previous accept intensity, - provided that the value of <c>exp(-Weight*(T(n) - T(n-1)) * AI(n-1)</c> is less than <c>MaxIntensity</c>; otherwise the - value is - </p> - <p><c>AI(n) = exp(-Weight*(T(n) - T(n-1)) * AI(n-1)</c>. - </p> - </item> - </list> - <p>The value of configuration parameter <c>Weight</c> controls the - speed with which the calculations of intensities will react to - changes in the underlying input intensity. The inverted value of - <c>Weight</c>, - </p> - <p><c>T = 1/Weight</c></p> - <p>can be thought of as the "time constant" - of the intensity calculation formulas. For example, if <c>Weight = 0.1</c>, then a change in the underlying input intensity will be - reflected in the <c>total</c> and <c>accept intensities</c> within - approximately 10 seconds. - </p> - <p>The overload process defines one alarm, which it sets using - <c>alarm_handler:set_alarm(Alarm)</c>. <c>Alarm</c> is defined - as: - </p> - <taglist> - <tag><c>{overload, []}</c></tag> - <item> - <p>This alarm is set when the current accept intensity exceeds - <c>MaxIntensity</c>. - </p> - </item> - </taglist> - <p>A new overload alarm is not set until the current accept - intensity has fallen below <c>MaxIntensity</c>. To prevent the - overload process from generating a lot of set/reset alarms, the - alarm is not reset until the current accept intensity has fallen - below 75% of <c>MaxIntensity</c>, and it is not until then that - the alarm can be set again. - </p> - </description> - <funcs> - <func> - <name>request() -> accept | reject</name> - <fsummary>Request to proceed with current job</fsummary> - <desc> - <p>Returns <c>accept</c> or <c>reject</c> depending on the - current value of the accept intensity. </p> - <p>The application - calling this function should be processed with the job in - question if the return value is <c>accept</c>; otherwise it - should not continue with that job. - </p> - </desc> - </func> - <func> - <name>get_overload_info() -> OverloadInfo</name> - <fsummary>Return current overload information data</fsummary> - <type> - <v>OverloadInfo = [{total_intensity, TotalIntensity}, {accept_intensity, AcceptIntensity}, {max_intensity, MaxIntensity}, {weight, Weight}, {total_requests, TotalRequests}, {accepted_requests, AcceptedRequests}].</v> - <v>TotalIntensity = float() > 0</v> - <v>AcceptIntensity = float() > 0</v> - <v>MaxIntensity = float() > 0</v> - <v>Weight = float() > 0</v> - <v>TotalRequests = integer()</v> - <v>AcceptedRequests = integer()</v> - </type> - <desc> - <p>Returns the current total and accept intensities, the - configuration parameters, and absolute counts of the total - number of requests, and accepted number of requests (since - the overload process was started).</p> - </desc> - </func> - </funcs> - - <section> - <title>See Also</title> - <p>alarm_handler(3), sasl(3) - </p> - </section> -</erlref> - |