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authorSiri Hansen <[email protected]>2015-12-11 14:11:38 +0100
committerSiri Hansen <[email protected]>2015-12-11 14:11:38 +0100
commit04f97abf89d39d8126c432341600268338ea5567 (patch)
treed29aabc1046732be00f230227e5e0131887d6bdb /lib/sasl/doc/src/overload.xml
parent76b9c79d439adffe1a55f5833e14f74ed1630390 (diff)
parentf84858101803153a04caeb1b300b80e376fc105d (diff)
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Merge branch 'siri/sasl/doc-editors/OTP-13000' into maint
* siri/sasl/doc-editors/OTP-13000: sasl: Editorial changes
Diffstat (limited to 'lib/sasl/doc/src/overload.xml')
-rw-r--r--lib/sasl/doc/src/overload.xml124
1 files changed, 59 insertions, 65 deletions
diff --git a/lib/sasl/doc/src/overload.xml b/lib/sasl/doc/src/overload.xml
index 35877220ab..5c3d00afeb 100644
--- a/lib/sasl/doc/src/overload.xml
+++ b/lib/sasl/doc/src/overload.xml
@@ -35,98 +35,88 @@
<module>overload</module>
<modulesummary>An Overload Regulation Process</modulesummary>
<description>
- <p><c>overload</c> is a process which indirectly regulates CPU
+ <p><c>overload</c> is a process that indirectly regulates the 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
+ function
+ <seealso marker="#request/0"><c>request/0</c></seealso>
+ 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>
+ 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, <c>MaxIntensity</c>
+ and <c>Weight</c>; 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>
+ <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>
+ <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 <c>total intensity</c>.</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>
+ <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 <c>accept intensity</c>,
+ if 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
+ speed with which the calculations of intensities 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>
+ <c>Weight</c>, <c>T = 1/Weight</c>, can be thought of as the
+ "time constant" of the intensity calculation formulas. For example,
+ if <c>Weight = 0.1</c>, a change in the underlying input intensity is
+ reflected in <c>total intensity</c> and <c>accept intensity</c> within
+ about 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>
+ <c>alarm_handler:set_alarm(Alarm)</c>. <c>Alarm</c> is defined
+ as follows:</p>
<taglist>
<tag><c>{overload, []}</c></tag>
<item>
- <p>This alarm is set when the current accept intensity exceeds
- <c>MaxIntensity</c>.
- </p>
+ <p>This alarm is set when the current <c>accept intensity</c> 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>
+ <p>A new request is not accepted until the current <c>accept
+ intensity</c> has fallen below <c>MaxIntensity</c>. To prevent the
+ overload process from generating many set/reset alarms, the
+ alarm is not reset until the current <c>accept intensity</c> has fallen
+ below 75% of <c>MaxIntensity</c>; 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>
+ <fsummary>Requests 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>
+ current value of the <c>accept intensity</c>.</p>
<p>The application
- calling this function should be processed with the job in
+ calling this function is to proceed with the job in
question if the return value is <c>accept</c>; otherwise it
- should not continue with that job.
- </p>
+ is not to continue with that job.</p>
</desc>
</func>
+
<func>
<name>get_overload_info() -> OverloadInfo</name>
- <fsummary>Return current overload information data</fsummary>
+ <fsummary>Returns 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>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>
@@ -135,18 +125,22 @@
<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>
+ <p>Returns:</p>
+ <list type="bulleted">
+ <item>Current total and accept intensities</item>
+ <item>Configuration parameters</item>
+ <item>Absolute counts of the total number of requests</item>
+ <item>Accepted number of requests (since the overload
+ process was started)</item>
+ </list>
</desc>
</func>
</funcs>
<section>
<title>See Also</title>
- <p>alarm_handler(3), sasl(3)
- </p>
+ <p><seealso marker="alarm_handler"><c>alarm_handler(3)</c></seealso>,
+ <seealso marker="sasl_app"><c>sasl(6)</c></seealso></p>
</section>
</erlref>