[PULL 0/1] Tracing patches

[PULL 0/1] Tracing patches

[Stefan Hajnoczi]

The following changes since commit dc65a5bdc9fa543690a775b50d4ffbeb22c56d6d:

  Merge remote-tracking branch 'remotes/dgibson/tags/ppc-for-5.0-20200108' into staging (2020-01-10 16:15:04 +0000)

are available in the Git repository at:

  https://github.com/stefanha/qemu.git tags/tracing-pull-request

for you to fetch changes up to 3f0097169bb60268cc5dda0c5ea47c31ab57b22f:

  trace: update qemu-trace-stap to Python 3 (2020-01-13 16:42:20 +0000)

----------------------------------------------------------------
Pull request

----------------------------------------------------------------

Stefan Hajnoczi (1):
  trace: update qemu-trace-stap to Python 3

 scripts/qemu-trace-stap | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

-- 
2.24.1

Re: [PULL 0/1] Tracing patches

[Peter Maydell]

On Tue, 14 Jan 2020 at 09:29, Stefan Hajnoczi <stefanha@redhat.com> wrote:
>
> The following changes since commit dc65a5bdc9fa543690a775b50d4ffbeb22c56d6d:
>
>   Merge remote-tracking branch 'remotes/dgibson/tags/ppc-for-5.0-20200108' into staging (2020-01-10 16:15:04 +0000)
>
> are available in the Git repository at:
>
>   https://github.com/stefanha/qemu.git tags/tracing-pull-request
>
> for you to fetch changes up to 3f0097169bb60268cc5dda0c5ea47c31ab57b22f:
>
>   trace: update qemu-trace-stap to Python 3 (2020-01-13 16:42:20 +0000)
>
> ----------------------------------------------------------------
> Pull request
>
> ----------------------------------------------------------------



Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/5.0
for any user-visible changes.

-- PMM

[PULL 0/1] Tracing patches

[Stefan Hajnoczi]

The following changes since commit 7623b5ba017f61de5d7c2bba12c6feb3d55091b1:

  Merge remote-tracking branch 'remotes/vivier2/tags/linux-user-for-5.1-pull-request' into staging (2020-07-06 11:40:10 +0100)

are available in the Git repository at:

  https://github.com/stefanha/qemu.git tags/tracing-pull-request

for you to fetch changes up to 27e08bab94f7c6ebe0b75938c98c394c969e3fd8:

  tracetool: work around ust <sys/sdt.h> include conflict (2020-07-07 16:07:14 +0100)

----------------------------------------------------------------
Pull request

Fix for a LTTng Userspace Tracer header problem.

----------------------------------------------------------------

Stefan Hajnoczi (1):
  tracetool: work around ust <sys/sdt.h> include conflict

 scripts/tracetool/backend/dtrace.py | 6 ++++++
 1 file changed, 6 insertions(+)

-- 
2.26.2

Re: [PULL 0/1] Tracing patches

[Peter Maydell]

On Tue, 7 Jul 2020 at 16:20, Stefan Hajnoczi <stefanha@redhat.com> wrote:
>
> The following changes since commit 7623b5ba017f61de5d7c2bba12c6feb3d55091b1:
>
>   Merge remote-tracking branch 'remotes/vivier2/tags/linux-user-for-5.1-pull-request' into staging (2020-07-06 11:40:10 +0100)
>
> are available in the Git repository at:
>
>   https://github.com/stefanha/qemu.git tags/tracing-pull-request
>
> for you to fetch changes up to 27e08bab94f7c6ebe0b75938c98c394c969e3fd8:
>
>   tracetool: work around ust <sys/sdt.h> include conflict (2020-07-07 16:07:14 +0100)
>
> ----------------------------------------------------------------
> Pull request
>
> Fix for a LTTng Userspace Tracer header problem.
>
> ----------------------------------------------------------------
>
> Stefan Hajnoczi (1):
>   tracetool: work around ust <sys/sdt.h> include conflict
>
>  scripts/tracetool/backend/dtrace.py | 6 ++++++
>  1 file changed, 6 insertions(+)


Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/5.1
for any user-visible changes.

-- PMM

[PULL 0/1] Tracing patches

[Stefan Hajnoczi]

The following changes since commit a3c3aaa846ad61b801e7196482dcf4afb8ba34e4:

  Merge tag 'pull-ppc-20231107' of https://gitlab.com/danielhb/qemu into staging (2023-11-08 20:35:00 +0800)

are available in the Git repository at:

  https://gitlab.com/stefanha/qemu.git tags/tracing-pull-request

for you to fetch changes up to 4d96307c5b4fac40c6ca25f38318b4b65d315de0:

  tracetool: avoid invalid escape in Python string (2023-11-09 15:03:02 +0800)

----------------------------------------------------------------
Pull request

----------------------------------------------------------------

Marc-André Lureau (1):
  tracetool: avoid invalid escape in Python string

 scripts/tracetool/__init__.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-- 
2.41.0

Re: [PULL 0/1] Tracing patches

[Stefan Hajnoczi]

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Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/8.2 for any user-visible changes.

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[PULL 0/1] Tracing patches

[Stefan Hajnoczi]

The following changes since commit 455f4440687fcee03e62d9b17b28162b638458af:

  Merge tag 'for_upstream' of https://git.kernel.org/pub/scm/virt/kvm/mst/qemu into staging (2023-12-26 06:07:16 -0500)

are available in the Git repository at:

  https://gitlab.com/stefanha/qemu.git tags/tracing-pull-request

for you to fetch changes up to 5db052306e69faf9f875ad6dec7c823c140990e0:

  tracing: install trace events file only if necessary (2023-12-27 05:01:55 -0500)

----------------------------------------------------------------
Pull request

----------------------------------------------------------------

Carlos Santos (1):
  tracing: install trace events file only if necessary

 trace/meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-- 
2.43.0

[PULL 0/1] Tracing patches

[Stefan Hajnoczi]

The following changes since commit f9edf32ea2e18a56de5d92f57e9d10565c822367:

  Merge tag 'pull-request-2025-02-11' of https://gitlab.com/thuth/qemu into staging (2025-02-11 13:27:32 -0500)

are available in the Git repository at:

  https://gitlab.com/stefanha/qemu.git tags/tracing-pull-request

for you to fetch changes up to 9976be3911a2d0503f026ae37c17077273bf30ee:

  scripts: improve error from qemu-trace-stap on missing 'stap' (2025-02-12 10:03:18 -0500)

----------------------------------------------------------------
Pull request

----------------------------------------------------------------

Daniel P. Berrangé (1):
  scripts: improve error from qemu-trace-stap on missing 'stap'

 scripts/qemu-trace-stap | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

-- 
2.48.1

[PULL 0/1] Tracing patches

[Stefan Hajnoczi]

The following changes since commit 5136598e2667f35ef3dc1d757616a266bd5eb3a2:

  Merge tag 'accel-cpus-20250309' of https://github.com/philmd/qemu into staging (2025-03-10 13:40:48 +0800)

are available in the Git repository at:

  https://gitlab.com/stefanha/qemu.git tags/tracing-pull-request

for you to fetch changes up to a506a1b16702aae69a43e782f225bdc0ec6545fc:

  trace/control-target: cleanup headers and make compilation unit common (2025-03-11 10:11:29 +0800)

----------------------------------------------------------------
Pull request

A tracing cleanup.

----------------------------------------------------------------

Pierrick Bouvier (1):
  trace/control-target: cleanup headers and make compilation unit common

 trace/control-target.c | 2 --
 trace/meson.build      | 4 +---
 2 files changed, 1 insertion(+), 5 deletions(-)

-- 
2.48.1

Re: [PULL 0/1] Tracing patches

[Stefan Hajnoczi]

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Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/10.0 for any user-visible changes.

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[PULL 0/1] Tracing patches

[Stefan Hajnoczi]

The following changes since commit 6322b753f798337835e205b6d805356bea582c86:

  Merge tag 'for_upstream' of https://git.kernel.org/pub/scm/virt/kvm/mst/qemu into staging (2025-06-02 14:52:45 -0400)

are available in the Git repository at:

  https://gitlab.com/stefanha/qemu.git tags/tracing-pull-request

for you to fetch changes up to ffcfb0faaa95fc6ca007f7dd989e390dacf936ca:

  trace/simple: seperate hot paths of tracing fucntions (2025-06-02 16:51:36 -0400)

----------------------------------------------------------------
Pull request

----------------------------------------------------------------

Tanish Desai (1):
  trace/simple: seperate hot paths of tracing fucntions

 scripts/tracetool/backend/simple.py | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

-- 
2.49.0

[PULL 1/1] trace/simple: seperate hot paths of tracing fucntions

[Stefan Hajnoczi]

From: Tanish Desai <tanishdesai37@gmail.com>

This change improves performance by moving the hot path of the trace_vhost_commit()(or any other trace function) logic to the header file.
Previously, even when the trace event was disabled, the function call chain:-
	trace_vhost_commit()(Or any other trace function) →  _nocheck__trace_vhost_commit() →  _simple_trace_vhost_commit()
	incurred a significant function prologue overhead before checking the trace state.

Disassembly of _simple_trace_vhost_commit() (from the .c file) showed that 11 out of the first 14 instructions were prologue-related, including:
0x10	stp x29, x30, [sp, #-64]!	Prologue: allocates 64-byte frame and saves old FP (x29) & LR (x30)
0x14	adrp x3, trace_events_enabled_count	Prologue: computes page-base of the trace-enable counter
0x18	adrp x2, __stack_chk_guard	Important (maybe prolog don't know?)(stack-protector): starts up the stack-canary load
0x1c	mov x29, sp	Prologue: sets new frame pointer
0x20	ldr x3, [x3]	Prologue: loads the actual trace-enabled count
0x24	stp x19, x20, [sp, #16]	Prologue: spills callee-saved regs used by this function (x19, x20)
0x28	and w20, w0, #0xff	Tracepoint setup: extracts the low-8 bits of arg0 as the “event boolean”
0x2c	ldr x2, [x2]	Prologue (cont’d): completes loading of the stack-canary value
0x30	and w19, w1, #0xff	Tracepoint setup: extracts low-8 bits of arg1
0x34	ldr w0, [x3]	Important: loads the current trace-enabled flag from memory
0x38	ldr x1, [x2]	Prologue (cont’d): reads the canary
0x3c	str x1, [sp, #56]	Prologue (cont’d): writes the canary into the new frame
0x40	mov x1, #0	Prologue (cont’d): zeroes out x1 for the upcoming branch test
0x44	cbnz w0, 0x88	Important: if tracing is disabled (w0==0) skip the heavy path entirely

The trace-enabled check happens after the prologue. This is wasteful when tracing is disabled, which is often the case in production.
To optimize this:
_nocheck__trace_vhost_commit() is now fully inlined in the .h file with
the hot path.It checks trace_event_get_state() before calling into _simple_trace_vhost_commit(), which remains in .c.
This avoids calling into the .c function altogether when the tracepoint is disabled, thereby skipping unnecessary prologue instructions.

This results in better performance by removing redundant instructions in the tracing fast path.

Signed-off-by: Tanish Desai <tanishdesai37@gmail.com>
Message-id: 20250528192528.3968-1-tanishdesai37@gmail.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 scripts/tracetool/backend/simple.py | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/scripts/tracetool/backend/simple.py b/scripts/tracetool/backend/simple.py
index a74d61fcd6..2688d4b64b 100644
--- a/scripts/tracetool/backend/simple.py
+++ b/scripts/tracetool/backend/simple.py
@@ -36,8 +36,17 @@ def generate_h_begin(events, group):
 
 
 def generate_h(event, group):
-    out('    _simple_%(api)s(%(args)s);',
+    event_id = 'TRACE_' + event.name.upper()
+    if "vcpu" in event.properties:
+        # already checked on the generic format code
+        cond = "true"
+    else:
+        cond = "trace_event_get_state(%s)" % event_id
+    out('    if (%(cond)s) {',
+        '        _simple_%(api)s(%(args)s);',
+        '    }',
         api=event.api(),
+        cond=cond,
         args=", ".join(event.args.names()))
 
 
@@ -72,22 +81,10 @@ def generate_c(event, group):
     if len(event.args) == 0:
         sizestr = '0'
 
-    event_id = 'TRACE_' + event.name.upper()
-    if "vcpu" in event.properties:
-        # already checked on the generic format code
-        cond = "true"
-    else:
-        cond = "trace_event_get_state(%s)" % event_id
-
     out('',
-        '    if (!%(cond)s) {',
-        '        return;',
-        '    }',
-        '',
         '    if (trace_record_start(&rec, %(event_obj)s.id, %(size_str)s)) {',
         '        return; /* Trace Buffer Full, Event Dropped ! */',
         '    }',
-        cond=cond,
         event_obj=event.api(event.QEMU_EVENT),
         size_str=sizestr)
 
-- 
2.49.0

Re: [PULL 0/1] Tracing patches

[Stefan Hajnoczi]

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Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/10.1 for any user-visible changes.

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[PULL 0/1] Tracing patches

[Stefan Hajnoczi]

The following changes since commit bc98ffdc7577e55ab8373c579c28fe24d600c40f:

  Merge tag 'pull-10.1-maintainer-may-2025-070625-1' of https://gitlab.com/stsquad/qemu into staging (2025-06-07 15:08:55 -0400)

are available in the Git repository at:

  https://gitlab.com/stefanha/qemu.git tags/tracing-pull-request

for you to fetch changes up to 9b8a5fd79df09efa7bfd728ba9e0c95297e42afa:

  meson: fix Windows build (2025-06-11 14:18:01 -0400)

----------------------------------------------------------------
Pull request

----------------------------------------------------------------

oltolm (1):
  meson: fix Windows build

 contrib/plugins/meson.build         |  2 +-
 plugins/meson.build                 |  2 +-
 scripts/tracetool/__init__.py       | 15 ++++++++++++---
 scripts/tracetool/backend/ftrace.py |  4 +---
 scripts/tracetool/backend/log.py    |  4 +---
 scripts/tracetool/backend/syslog.py |  4 +---
 tests/functional/meson.build        |  4 +---
 tests/include/meson.build           |  2 +-
 tests/tcg/plugins/meson.build       |  2 +-
 trace/meson.build                   |  5 +++--
 10 files changed, 23 insertions(+), 21 deletions(-)

-- 
2.49.0

[PULL 0/1] Tracing patches

[Stefan Hajnoczi]

The following changes since commit 56a3033abcfcf72a2f4f1376a605a0b1ad526b67:

  Merge tag 'pull-request-2025-07-21' of https://gitlab.com/thuth/qemu into staging (2025-07-21 06:34:56 -0400)

are available in the Git repository at:

  https://gitlab.com/stefanha/qemu.git tags/tracing-pull-request

for you to fetch changes up to 50700e97d85e435363ca4525754b5f00b13491c0:

  trace: log.py: human-readable timestamp (2025-07-21 14:02:52 -0400)

----------------------------------------------------------------
Pull request

----------------------------------------------------------------

Vladimir Sementsov-Ogievskiy (1):
  trace: log.py: human-readable timestamp

 scripts/tracetool/backend/log.py | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

-- 
2.50.1

[PULL 0/1] Tracing patches

[Stefan Hajnoczi]

The following changes since commit ebcc602aae19c06a4f492da3920b64c8033f0d7f:

  Merge tag 'display-20250718-pull-request' of https://gitlab.com/kraxel/qemu into staging (2025-07-21 12:24:36 -0400)

are available in the Git repository at:

  https://gitlab.com/stefanha/qemu.git tags/tracing-pull-request

for you to fetch changes up to 2b1791323e7ce043cbc3857699e5d5b0ad021cbc:

  tracetool: removed the unused vcpu property (2025-07-22 10:44:49 -0400)

----------------------------------------------------------------
Pull request

Tanish's removal of the remnants of the "vcpu" property.

----------------------------------------------------------------

Tanish Desai (1):
  tracetool: removed the unused vcpu property

 scripts/tracetool/__init__.py       | 2 +-
 scripts/tracetool/backend/log.py    | 6 +-----
 scripts/tracetool/backend/simple.py | 6 +-----
 scripts/tracetool/backend/syslog.py | 6 +-----
 4 files changed, 4 insertions(+), 16 deletions(-)

-- 
2.50.1

[PULL 0/1] Tracing patches

[Stefan Hajnoczi]

The following changes since commit 9e601684dc24a521bb1d23215a63e5c6e79ea0bb:

  Update version for the v10.1.0-rc0 release (2025-07-22 15:48:48 -0400)

are available in the Git repository at:

  https://gitlab.com/stefanha/qemu.git tags/tracing-pull-request

for you to fetch changes up to 012842c075520dbe1bd96a2fdcf4e218874ba443:

  log: make '-msg timestamp=on' apply to all qemu_log usage (2025-07-24 10:12:21 -0400)

----------------------------------------------------------------
Pull request

This commit is still worth having in QEMU 10.1 for the all-round improvements
made (consistent timestamping, binary size reduction, header pollution cleanup)
even if it's debatable whether this is a bug fix.

----------------------------------------------------------------

Daniel P. Berrangé (1):
  log: make '-msg timestamp=on' apply to all qemu_log usage

 util/log.c                       | 20 +++++++++++++++++++-
 scripts/tracetool/backend/log.py | 14 +-------------
 2 files changed, 20 insertions(+), 14 deletions(-)

-- 
2.50.1

Re: [PULL 0/1] Tracing patches

[Stefan Hajnoczi]

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Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/10.1 for any user-visible changes.

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