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Mon, 12 Aug 2024 16:19:49 -0700 (PDT) From: Pierrick Bouvier To: qemu-devel@nongnu.org Cc: Mahmoud Mandour , Pierrick Bouvier , Alexandre Iooss , Paolo Bonzini , Richard Henderson , =?UTF-8?q?Alex=20Benn=C3=A9e?= Subject: [PATCH v3] docs/devel: update tcg-plugins page Date: Mon, 12 Aug 2024 16:19:45 -0700 Message-Id: <20240812231945.169310-1-pierrick.bouvier@linaro.org> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:20::d35; envelope-from=pierrick.bouvier@linaro.org; helo=mail-io1-xd35.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @linaro.org) X-ZM-MESSAGEID: 1723504818561116600 Content-Type: text/plain; charset="utf-8" Reflect recent changes on API (inline ops) and new plugins. Signed-off-by: Pierrick Bouvier --- docs/about/emulation.rst | 49 ++++++++++++++++++++++++++++++++------ docs/devel/tcg-plugins.rst | 13 ++++++---- 2 files changed, 50 insertions(+), 12 deletions(-) diff --git a/docs/about/emulation.rst b/docs/about/emulation.rst index c03033e4e95..eea1261baac 100644 --- a/docs/about/emulation.rst +++ b/docs/about/emulation.rst @@ -207,8 +207,8 @@ Once built a program can be run with multiple plugins l= oaded each with their own arguments:: =20 $QEMU $OTHER_QEMU_ARGS \ - -plugin contrib/plugin/libhowvec.so,inline=3Don,count=3Dhint \ - -plugin contrib/plugin/libhotblocks.so + -plugin contrib/plugins/libhowvec.so,inline=3Don,count=3Dhint \ + -plugin contrib/plugins/libhotblocks.so =20 Arguments are plugin specific and can be used to modify their behaviour. In this case the howvec plugin is being asked to use inline @@ -219,6 +219,14 @@ Linux user-mode emulation also evaluates the environme= nt variable =20 QEMU_PLUGIN=3D"file=3Dcontrib/plugins/libhowvec.so,inline=3Don,count=3Dh= int" $QEMU =20 +QEMU plugins avoid to write directly to stdin/stderr, and use the log prov= ided +by the API (see function ``qemu_plugin_outs``). +To show output, you may use this additional parameter:: + + $QEMU $OTHER_QEMU_ARGS \ + -d plugin \ + -plugin contrib/plugins/libhowvec.so,inline=3Don,count=3Dhint + Example Plugins ~~~~~~~~~~~~~~~ =20 @@ -260,8 +268,7 @@ Behaviour can be tweaked with the following arguments: * - Option - Description * - inline=3Dtrue|false - - Use faster inline addition of a single counter. Not per-cpu and not - thread safe. + - Use faster inline addition of a single counter. * - idle=3Dtrue|false - Dump the current execution stats whenever the guest vCPU idles =20 @@ -381,6 +388,15 @@ run:: 160 1 0 135 1 0 =20 +Test inline operations +...................... + +``tests/plugins/inline.c`` + +This plugin is used for testing all inline operations, conditional callbac= ks and +scoreboard. It prints a per-cpu summary of all events. + + Hot Blocks .......... =20 @@ -394,9 +410,6 @@ with linux-user execution as system emulation tends to = generate re-translations as blocks from different programs get swapped in and out of system memory. =20 -If your program is single-threaded you can use the ``inline`` option for -slightly faster (but not thread safe) counters. - Example:: =20 $ qemu-aarch64 \ @@ -736,6 +749,28 @@ The plugin will log the reason of exit, for example:: =20 0xd4 reached, exiting =20 +Limit instructions per second +............................. + +This plugin can limit the number of Instructions Per Second that are execu= ted:: + + # get number of instructions + $ num_insn=3D$(./build/qemu-x86_64 -plugin ./build/tests/plugin/libins= n.so -d plugin /bin/true |& grep total | sed -e 's/.*: //') + # limit speed to execute in 10 seconds + $ time ./build/qemu-x86_64 -plugin ./build/contrib/plugins/libips.so,i= ps=3D$(($num_insn/10)) /bin/true + real 10.000s + + +.. list-table:: IPS arguments + :widths: 20 80 + :header-rows: 1 + + * - Option + - Description + * - ips=3DN + - Maximum number of instructions per cpu that can be executed in one s= econd. + The plugin will sleep when the given number of instructions is reach= ed. + Other emulation features ------------------------ =20 diff --git a/docs/devel/tcg-plugins.rst b/docs/devel/tcg-plugins.rst index d8725c2854a..9463692c411 100644 --- a/docs/devel/tcg-plugins.rst +++ b/docs/devel/tcg-plugins.rst @@ -61,11 +61,14 @@ translation event the plugin has an option to enumerate= the instructions in a block of instructions and optionally register callbacks to some or all instructions when they are executed. =20 -There is also a facility to add an inline event where code to -increment a counter can be directly inlined with the translation. -Currently only a simple increment is supported. This is not atomic so -can miss counts. If you want absolute precision you should use a -callback which can then ensure atomicity itself. +There is also a facility to add inline instructions doing various operatio= ns, +like adding or storing an immediate value. It is also possible to execute a +callback conditionally, with condition being evaluated inline. All those i= nline +operations are associated to a ``scoreboard``, which is a thread-local sto= rage +automatically expanded when new cores/threads are created and that can be +accessed/modified in a thread-safe way without any lock needed. Combining = inline +operations and conditional callbacks offer a more efficient way to instrum= ent +binaries, compared to classic callbacks. =20 Finally when QEMU exits all the registered *atexit* callbacks are invoked. --=20 2.39.2