Blame SOURCES/kvm-trace-add-tracetool-simpletrace_stap-format.patch

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From a38cb7ff39accd9ea600e2409866eb12fb3b8871 Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Tue, 7 Oct 2014 14:06:55 +0200
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Subject: [PATCH 37/43] trace: add tracetool simpletrace_stap format
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Message-id: <1412690820-31016-7-git-send-email-stefanha@redhat.com>
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Patchwork-id: 61611
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O-Subject: [RHEL7.1 qemu-kvm PATCH 06/11] trace: add tracetool simpletrace_stap format
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Bugzilla: 1088112
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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This new tracetool "format" generates a SystemTap .stp file that outputs
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simpletrace binary trace data.
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In contrast to simpletrace or ftrace, SystemTap does not define its own
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trace format.  All output from SystemTap is generated by .stp files.
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This patch lets us generate a .stp file that outputs in the simpletrace
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binary format.
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This makes it possible to reuse simpletrace.py to analyze traces
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recorded using SystemTap.  The simpletrace binary format is especially
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useful for long-running traces like flight-recorder mode where string
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formatting can be expensive.
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 3f8b112d6b9ab65e165096582c78154dda1adc69)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Downstream tracetool does not have the code reorganization from the
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multi-backend tracing changes.  Therefore the stap generation has to
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happen in scripts/tracetool/backend/dtrace.py while the
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scripts/tracetool/format/simpletrace_stap.py file just emits the file
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header.
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Remember to import tracetool.backend.simple is_string() in dtrace.py.
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Also note that scripts/tracetool/__init__.py filters out disabled events
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so we don't need to skip them explicitly.
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 scripts/tracetool/backend/dtrace.py          | 47 ++++++++++++++++++++++++++++
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 scripts/tracetool/format/simpletrace_stap.py | 21 +++++++++++++
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 2 files changed, 68 insertions(+)
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 create mode 100644 scripts/tracetool/format/simpletrace_stap.py
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diff --git a/scripts/tracetool/backend/dtrace.py b/scripts/tracetool/backend/dtrace.py
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index 614316f..2d8cd2d 100644
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--- a/scripts/tracetool/backend/dtrace.py
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+++ b/scripts/tracetool/backend/dtrace.py
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@@ -14,6 +14,7 @@ __email__      = "stefanha@linux.vnet.ibm.com"
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 from tracetool import out
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+from tracetool.backend.simple import is_string
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 PUBLIC = True
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@@ -112,3 +113,49 @@ def stap(events):
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         out('}')
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     out()
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+
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+
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+def simpletrace_stap(events):
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+    for event_id, e in enumerate(events):
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+        out('probe %(probeprefix)s.simpletrace.%(name)s = %(probeprefix)s.%(name)s ?',
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+            '{',
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+            probeprefix=_probeprefix(),
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+            name=e.name)
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+
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+        # Calculate record size
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+        sizes = ['24'] # sizeof(TraceRecord)
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+        for type_, name in e.args:
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+            name = stap_escape(name)
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+            if is_string(type_):
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+                out('    try {',
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+                    '        arg%(name)s_str = %(name)s ? user_string_n(%(name)s, 512) : "<null>"',
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+                    '    } catch {}',
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+                    '    arg%(name)s_len = strlen(arg%(name)s_str)',
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+                    name=name)
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+                sizes.append('4 + arg%s_len' % name)
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+            else:
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+                sizes.append('8')
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+        sizestr = ' + '.join(sizes)
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+
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+        # Generate format string and value pairs for record header and arguments
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+        fields = [('8b', str(event_id)),
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+                  ('8b', 'gettimeofday_ns()'),
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+                  ('4b', sizestr),
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+                  ('4b', 'pid()')]
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+        for type_, name in e.args:
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+            name = stap_escape(name)
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+            if is_string(type_):
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+                fields.extend([('4b', 'arg%s_len' % name),
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+                               ('.*s', 'arg%s_len, arg%s_str' % (name, name))])
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+            else:
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+                fields.append(('8b', name))
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+
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+        # Emit the entire record in a single SystemTap printf()
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+        fmt_str = '%'.join(fmt for fmt, _ in fields)
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+        arg_str = ', '.join(arg for _, arg in fields)
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+        out('    printf("%%%(fmt_str)s", %(arg_str)s)',
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+            fmt_str=fmt_str, arg_str=arg_str)
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+
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+        out('}')
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+
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+    out()
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diff --git a/scripts/tracetool/format/simpletrace_stap.py b/scripts/tracetool/format/simpletrace_stap.py
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new file mode 100644
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index 0000000..b8daa03
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--- /dev/null
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+++ b/scripts/tracetool/format/simpletrace_stap.py
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@@ -0,0 +1,21 @@
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+#!/usr/bin/env python
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+# -*- coding: utf-8 -*-
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+
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+"""
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+Generate .stp file that outputs simpletrace binary traces (DTrace with SystemTAP only).
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+"""
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+
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+__author__     = "Stefan Hajnoczi <redhat.com>"
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+__copyright__  = "Copyright (C) 2014, Red Hat, Inc."
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+__license__    = "GPL version 2 or (at your option) any later version"
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+
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+__maintainer__ = "Stefan Hajnoczi"
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+__email__      = "stefanha@redhat.com"
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+
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+
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+from tracetool import out
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+
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+
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+def begin(events):
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+    out('/* This file is autogenerated by tracetool, do not edit. */',
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+        '')
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-- 
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1.8.3.1
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