On 2025/05/22 1:42, Alex Bennée wrote:
The default is we update time every 1/10th of a second or so. However
for some cases we might want to update time more frequently. Allow
this to be set via the command line through the ipq argument.
Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouv...@linaro.org>
---
v3
- error checking for ipq
v2
- checkpatch fixes.
---
docs/about/emulation.rst | 4 ++++
contrib/plugins/ips.c | 15 ++++++++++++++-
2 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/docs/about/emulation.rst b/docs/about/emulation.rst
index a72591ee4d..456d01d5b0 100644
--- a/docs/about/emulation.rst
+++ b/docs/about/emulation.rst
@@ -811,6 +811,10 @@ This plugin can limit the number of Instructions Per
Second that are executed::
* - ips=N
- Maximum number of instructions per cpu that can be executed in one
second.
The plugin will sleep when the given number of instructions is reached.
+ * - ipq=N
+ - Instructions per quantum. How many instructions before we re-calculate
time.
+ The lower the number the more accurate time will be, but the less
efficient the plugin.
+ Defaults to ips/10
Other emulation features
------------------------
diff --git a/contrib/plugins/ips.c b/contrib/plugins/ips.c
index eb4418c25b..f1523cbee3 100644
--- a/contrib/plugins/ips.c
+++ b/contrib/plugins/ips.c
@@ -145,6 +145,8 @@ QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t
id,
const qemu_info_t *info, int argc,
char **argv)
{
+ bool ipq_set = false;
+
for (int i = 0; i < argc; i++) {
char *opt = argv[i];
g_auto(GStrv) tokens = g_strsplit(opt, "=", 2);
@@ -175,6 +177,14 @@ QEMU_PLUGIN_EXPORT int
qemu_plugin_install(qemu_plugin_id_t id,
return -1;
}
}
+ } else if (g_strcmp0(tokens[0], "ipq") == 0) {
+ max_insn_per_quantum = g_ascii_strtoull(tokens[1], NULL, 10);
+
+ if (max_insn_per_quantum == 0 || max_insn_per_quantum ==
G_MAXUINT64) {
+ fprintf(stderr, "bad ipq value: %s\n", g_strerror(errno));
This check should follow one of ips.
First, it should check errno. Otherwise it may emit a cryptic message
saying: "bad ipq value: Success".
max_insn_per_quantum == G_MAXUINT64 is unnecessary. A sufficiently large
value of max_insn_per_quantum should result in the same behavior anyway:
a quantum never ends.
Following the check of ips is an easy way to implement a correct
checking and it also ensures consistency.
+ return -1;
+ }
+ ipq_set = true;
} else {
fprintf(stderr, "option parsing failed: %s\n", opt);
return -1;
@@ -182,7 +192,10 @@ QEMU_PLUGIN_EXPORT int
qemu_plugin_install(qemu_plugin_id_t id,
}
vcpus = qemu_plugin_scoreboard_new(sizeof(vCPUTime));
- max_insn_per_quantum = max_insn_per_second / NUM_TIME_UPDATE_PER_SEC;
+
+ if (!ipq_set) {
+ max_insn_per_quantum = max_insn_per_second / NUM_TIME_UPDATE_PER_SEC;
+ }
if (max_insn_per_quantum == 0) {
fprintf(stderr, "minimum of %d instructions per second needed\n",
