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authorRickard Green <[email protected]>2016-01-05 16:55:04 +0100
committerRickard Green <[email protected]>2016-01-20 11:10:37 +0100
commit858c6f7fa44f7b2dc363b359198d6522dd60e914 (patch)
treefdad35b9a7a9904d7dc4586aced86c79fb46a78c /erts/doc/src
parentdf18cd270ad682cedc8c21990641b0bdb8788092 (diff)
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Introduce time warp safe trace timestamp formats
New timestamp options for trace, sequential trace, and system profile: - monotonic_timestamp - strict_monotonic_timestamp
Diffstat (limited to 'erts/doc/src')
-rw-r--r--erts/doc/src/erlang.xml64
1 files changed, 60 insertions, 4 deletions
diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml
index 64eebec936..79d3f66ea8 100644
--- a/erts/doc/src/erlang.xml
+++ b/erts/doc/src/erlang.xml
@@ -7739,6 +7739,13 @@ ok
<c>inactive</c>, and later <c>active</c> when the port
callback returns.</p>
</item>
+ <tag><c>monotonic_timestamp</c></tag>
+ <item>
+ <p>Timestamps in profile messages will use
+ <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang
+ monotonic time</seealso>. The time-stamp (Ts) has the same
+ format and value as produced by <c>erlang:monotonic_time()</c>.</p>
+ </item>
<tag><c>runnable_procs</c></tag>
<item>
<p>If a process is put into or removed from the run queue, a
@@ -7759,6 +7766,25 @@ ok
<c>{profile, scheduler, Id, State, NoScheds, Ts}</c>, is
sent to <c><anno>ProfilerPid</anno></c>.</p>
</item>
+ <tag><c>strict_monotonic_timestamp</c></tag>
+ <item>
+ <p>Timestamps in profile messages will consisting of
+ <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang
+ monotonic time</seealso> and a monotonically increasing
+ integer. The time-stamp (Ts) has the same format and value
+ as produced by <c>{erlang:monotonic_time(),
+ erlang:unique_integer([monotonic])}</c>.</p>
+ </item>
+ <tag><c>timestamp</c></tag>
+ <item>
+ <p>Timestamps in profile messages will include a
+ time-stamp (Ts) that has the same form as returned by
+ <c>erlang:now()</c>. This is also the default if no
+ timestamp flag is given. If <c>cpu_timestamp</c> has
+ been enabled via <c>erlang:trace/3</c>, this will also
+ effect the timestamp produced in profiling messages
+ when <c>timestamp</c> flag is enabled.</p>
+ </item>
</taglist>
<note><p><c>erlang:system_profile</c> is considered experimental
and its behavior can change in a future release.</p>
@@ -8118,7 +8144,10 @@ timestamp() ->
<tag><c>cpu_timestamp</c></tag>
<item>
<p>A global trace flag for the Erlang node that makes all
- trace time-stamps to be in CPU time, not wall clock time.
+ trace time-stamps using the <c>timestamp</c> flag to be
+ in CPU time, not wall clock time. That is, <c>cpu_timestamp</c>
+ will not be used if <c>monotonic_timestamp</c>, or
+ <c>strict_monotonic_timestamp</c> is enabled.
Only allowed with <c>PidSpec==all</c>. If the host
machine OS does not support high-resolution
CPU time measurements, <c>trace/3</c> exits with
@@ -8126,6 +8155,26 @@ timestamp() ->
not synchronize this value across cores, so be prepared
that time might seem to go backwards when using this option.</p>
</item>
+ <tag><c>monotonic_timestamp</c></tag>
+ <item>
+ <p>Includes an
+ <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang
+ monotonic time</seealso> time-stamp in all trace messages. The
+ time-stamp (Ts) has the same format and value as produced by
+ <c>erlang:monotonic_time()</c>. This flag overrides
+ the <c>cpu_timestamp</c> flag.</p>
+ </item>
+ <tag><c>strict_monotonic_timestamp</c></tag>
+ <item>
+ <p>Includes an timestamp consisting of
+ <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang
+ monotonic time</seealso> and a monotonically increasing
+ integer in all trace messages. The time-stamp (Ts) has the
+ same format and value as produced by
+ <c>{erlang:monotonic_time(),
+ erlang:unique_integer([monotonic])}</c>. This flag overrides
+ the <c>cpu_timestamp</c> flag.</p>
+ </item>
<tag><c>arity</c></tag>
<item>
<p>Used with the <c>call</c> trace flag.
@@ -8172,9 +8221,16 @@ timestamp() ->
in the following list. <c>Pid</c> is the process identifier of the
traced process in which the traced event has occurred. The
third tuple element is the message tag.</p>
- <p>If flag <c>timestamp</c> is given, the first tuple
- element is <c>trace_ts</c> instead, and the time-stamp
- is added last in the message tuple.</p>
+ <p>If flag <c>timestamp</c>, <c>strict_monotonic_timestamp</c>, or
+ <c>monotonic_timestamp</c> is given, the first tuple
+ element is <c>trace_ts</c> instead, and the time-stamp
+ is added as an extra element last in the message tuple. If
+ multiple timestamp flags are passed, <c>timestamp</c> has
+ precedence over <c>strict_monotonic_timestamp</c> which
+ in turn has precedence over <c>monotonic_timestamp</c>. All
+ timestamp flags are remembered, so if two are passed
+ and the one with highest precedence later is disabled
+ the other one will become active.</p>
<marker id="trace_3_trace_messages"></marker>
<taglist>
<tag><c>{trace, Pid, 'receive', Msg}</c></tag>