| Message ID | 20240620152220.2192768-11-alex.bennee@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | maintainer updates pre-PR (gdbstub, plugins, time control) | expand |
Reviewed-by: Alwalid Salama <quic_asalama@qualcomm.com> On 6/20/2024 5:22 PM, Alex Bennée wrote: > From: Pierrick Bouvier <pierrick.bouvier@linaro.org> > > This plugin uses the new time control interface to make decisions > about the state of time during the emulation. The algorithm is > currently very simple. The user specifies an ips rate which applies > per core. If the core runs ahead of its allocated execution time the > plugin sleeps for a bit to let real time catch up. Either way time is > updated for the emulation as a function of total executed instructions > with some adjustments for cores that idle. > > Examples > -------- > > Slow down execution of /bin/true: > $ num_insn=$(./build/qemu-x86_64 -plugin ./build/tests/plugin/libinsn.so -d plugin /bin/true |& grep total | sed -e 's/.*: //') > $ time ./build/qemu-x86_64 -plugin ./build/contrib/plugins/libips.so,ips=$(($num_insn/4)) /bin/true > real 4.000s > > Boot a Linux kernel simulating a 250MHz cpu: > $ /build/qemu-system-x86_64 -kernel /boot/vmlinuz-6.1.0-21-amd64 -append "console=ttyS0" -plugin ./build/contrib/plugins/libips.so,ips=$((250*1000*1000)) -smp 1 -m 512 > check time until kernel panic on serial0 > > Tested in system mode by booting a full debian system, and using: > $ sysbench cpu run > Performance decrease linearly with the given number of ips. > > Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org> > Signed-off-by: Alex Bennée <alex.bennee@linaro.org> > Message-Id: <20240530220610.1245424-7-pierrick.bouvier@linaro.org> > > --- > v2 > - more explicit Instructions Per Second (IPS)! > --- > contrib/plugins/ips.c | 164 +++++++++++++++++++++++++++++++++++++++ > contrib/plugins/Makefile | 1 + > 2 files changed, 165 insertions(+) > create mode 100644 contrib/plugins/ips.c > > diff --git a/contrib/plugins/ips.c b/contrib/plugins/ips.c > new file mode 100644 > index 0000000000..29fa556d0f > --- /dev/null > +++ b/contrib/plugins/ips.c > @@ -0,0 +1,164 @@ > +/* > + * Instructions Per Second (IPS) rate limiting plugin. > + * > + * This plugin can be used to restrict the execution of a system to a > + * particular number of Instructions Per Second (IPS). This controls > + * time as seen by the guest so while wall-clock time may be longer > + * from the guests point of view time will pass at the normal rate. > + * > + * This uses the new plugin API which allows the plugin to control > + * system time. > + * > + * Copyright (c) 2023 Linaro Ltd > + * > + * SPDX-License-Identifier: GPL-2.0-or-later > + */ > + > +#include <stdio.h> > +#include <glib.h> > +#include <qemu-plugin.h> > + > +QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION; > + > +/* how many times do we update time per sec */ > +#define NUM_TIME_UPDATE_PER_SEC 10 > +#define NSEC_IN_ONE_SEC (1000 * 1000 * 1000) > + > +static GMutex global_state_lock; > + > +static uint64_t max_insn_per_second = 1000 * 1000 * 1000; /* ips per core, per second */ > +static uint64_t max_insn_per_quantum; /* trap every N instructions */ > +static int64_t virtual_time_ns; /* last set virtual time */ > + > +static const void *time_handle; > + > +typedef struct { > + uint64_t total_insn; > + uint64_t quantum_insn; /* insn in last quantum */ > + int64_t last_quantum_time; /* time when last quantum started */ > +} vCPUTime; > + > +struct qemu_plugin_scoreboard *vcpus; > + > +/* return epoch time in ns */ > +static int64_t now_ns(void) > +{ > + return g_get_real_time() * 1000; > +} > + > +static uint64_t num_insn_during(int64_t elapsed_ns) > +{ > + double num_secs = elapsed_ns / (double) NSEC_IN_ONE_SEC; > + return num_secs * (double) max_insn_per_second; > +} > + > +static int64_t time_for_insn(uint64_t num_insn) > +{ > + double num_secs = (double) num_insn / (double) max_insn_per_second; > + return num_secs * (double) NSEC_IN_ONE_SEC; > +} > + > +static void update_system_time(vCPUTime *vcpu) > +{ > + int64_t elapsed_ns = now_ns() - vcpu->last_quantum_time; > + uint64_t max_insn = num_insn_during(elapsed_ns); > + > + if (vcpu->quantum_insn >= max_insn) { > + /* this vcpu ran faster than expected, so it has to sleep */ > + uint64_t insn_advance = vcpu->quantum_insn - max_insn; > + uint64_t time_advance_ns = time_for_insn(insn_advance); > + int64_t sleep_us = time_advance_ns / 1000; > + g_usleep(sleep_us); > + } > + > + vcpu->total_insn += vcpu->quantum_insn; > + vcpu->quantum_insn = 0; > + vcpu->last_quantum_time = now_ns(); > + > + /* based on total number of instructions, what should be the new time? */ > + int64_t new_virtual_time = time_for_insn(vcpu->total_insn); > + > + g_mutex_lock(&global_state_lock); > + > + /* Time only moves forward. Another vcpu might have updated it already. */ > + if (new_virtual_time > virtual_time_ns) { > + qemu_plugin_update_ns(time_handle, new_virtual_time); > + virtual_time_ns = new_virtual_time; > + } > + > + g_mutex_unlock(&global_state_lock); > +} > + > +static void vcpu_init(qemu_plugin_id_t id, unsigned int cpu_index) > +{ > + vCPUTime *vcpu = qemu_plugin_scoreboard_find(vcpus, cpu_index); > + vcpu->total_insn = 0; > + vcpu->quantum_insn = 0; > + vcpu->last_quantum_time = now_ns(); > +} > + > +static void vcpu_exit(qemu_plugin_id_t id, unsigned int cpu_index) > +{ > + vCPUTime *vcpu = qemu_plugin_scoreboard_find(vcpus, cpu_index); > + update_system_time(vcpu); > +} > + > +static void every_quantum_insn(unsigned int cpu_index, void *udata) > +{ > + vCPUTime *vcpu = qemu_plugin_scoreboard_find(vcpus, cpu_index); > + g_assert(vcpu->quantum_insn >= max_insn_per_quantum); > + update_system_time(vcpu); > +} > + > +static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb) > +{ > + size_t n_insns = qemu_plugin_tb_n_insns(tb); > + qemu_plugin_u64 quantum_insn = > + qemu_plugin_scoreboard_u64_in_struct(vcpus, vCPUTime, quantum_insn); > + /* count (and eventually trap) once per tb */ > + qemu_plugin_register_vcpu_tb_exec_inline_per_vcpu( > + tb, QEMU_PLUGIN_INLINE_ADD_U64, quantum_insn, n_insns); > + qemu_plugin_register_vcpu_tb_exec_cond_cb( > + tb, every_quantum_insn, > + QEMU_PLUGIN_CB_NO_REGS, QEMU_PLUGIN_COND_GE, > + quantum_insn, max_insn_per_quantum, NULL); > +} > + > +static void plugin_exit(qemu_plugin_id_t id, void *udata) > +{ > + qemu_plugin_scoreboard_free(vcpus); > +} > + > +QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id, > + const qemu_info_t *info, int argc, > + char **argv) > +{ > + for (int i = 0; i < argc; i++) { > + char *opt = argv[i]; > + g_auto(GStrv) tokens = g_strsplit(opt, "=", 2); > + if (g_strcmp0(tokens[0], "ips") == 0) { > + max_insn_per_second = g_ascii_strtoull(tokens[1], NULL, 10); > + if (!max_insn_per_second && errno) { > + fprintf(stderr, "%s: couldn't parse %s (%s)\n", > + __func__, tokens[1], g_strerror(errno)); > + return -1; > + } > + } else { > + fprintf(stderr, "option parsing failed: %s\n", opt); > + return -1; > + } > + } > + > + vcpus = qemu_plugin_scoreboard_new(sizeof(vCPUTime)); > + max_insn_per_quantum = max_insn_per_second / NUM_TIME_UPDATE_PER_SEC; > + > + time_handle = qemu_plugin_request_time_control(); > + g_assert(time_handle); > + > + qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans); > + qemu_plugin_register_vcpu_init_cb(id, vcpu_init); > + qemu_plugin_register_vcpu_exit_cb(id, vcpu_exit); > + qemu_plugin_register_atexit_cb(id, plugin_exit, NULL); > + > + return 0; > +} > diff --git a/contrib/plugins/Makefile b/contrib/plugins/Makefile > index 0b64d2c1e3..449ead1130 100644 > --- a/contrib/plugins/Makefile > +++ b/contrib/plugins/Makefile > @@ -27,6 +27,7 @@ endif > NAMES += hwprofile > NAMES += cache > NAMES += drcov > +NAMES += ips > > ifeq ($(CONFIG_WIN32),y) > SO_SUFFIX := .dll
diff --git a/contrib/plugins/ips.c b/contrib/plugins/ips.c new file mode 100644 index 0000000000..29fa556d0f --- /dev/null +++ b/contrib/plugins/ips.c @@ -0,0 +1,164 @@ +/* + * Instructions Per Second (IPS) rate limiting plugin. + * + * This plugin can be used to restrict the execution of a system to a + * particular number of Instructions Per Second (IPS). This controls + * time as seen by the guest so while wall-clock time may be longer + * from the guests point of view time will pass at the normal rate. + * + * This uses the new plugin API which allows the plugin to control + * system time. + * + * Copyright (c) 2023 Linaro Ltd + * + * SPDX-License-Identifier: GPL-2.0-or-later + */ + +#include <stdio.h> +#include <glib.h> +#include <qemu-plugin.h> + +QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION; + +/* how many times do we update time per sec */ +#define NUM_TIME_UPDATE_PER_SEC 10 +#define NSEC_IN_ONE_SEC (1000 * 1000 * 1000) + +static GMutex global_state_lock; + +static uint64_t max_insn_per_second = 1000 * 1000 * 1000; /* ips per core, per second */ +static uint64_t max_insn_per_quantum; /* trap every N instructions */ +static int64_t virtual_time_ns; /* last set virtual time */ + +static const void *time_handle; + +typedef struct { + uint64_t total_insn; + uint64_t quantum_insn; /* insn in last quantum */ + int64_t last_quantum_time; /* time when last quantum started */ +} vCPUTime; + +struct qemu_plugin_scoreboard *vcpus; + +/* return epoch time in ns */ +static int64_t now_ns(void) +{ + return g_get_real_time() * 1000; +} + +static uint64_t num_insn_during(int64_t elapsed_ns) +{ + double num_secs = elapsed_ns / (double) NSEC_IN_ONE_SEC; + return num_secs * (double) max_insn_per_second; +} + +static int64_t time_for_insn(uint64_t num_insn) +{ + double num_secs = (double) num_insn / (double) max_insn_per_second; + return num_secs * (double) NSEC_IN_ONE_SEC; +} + +static void update_system_time(vCPUTime *vcpu) +{ + int64_t elapsed_ns = now_ns() - vcpu->last_quantum_time; + uint64_t max_insn = num_insn_during(elapsed_ns); + + if (vcpu->quantum_insn >= max_insn) { + /* this vcpu ran faster than expected, so it has to sleep */ + uint64_t insn_advance = vcpu->quantum_insn - max_insn; + uint64_t time_advance_ns = time_for_insn(insn_advance); + int64_t sleep_us = time_advance_ns / 1000; + g_usleep(sleep_us); + } + + vcpu->total_insn += vcpu->quantum_insn; + vcpu->quantum_insn = 0; + vcpu->last_quantum_time = now_ns(); + + /* based on total number of instructions, what should be the new time? */ + int64_t new_virtual_time = time_for_insn(vcpu->total_insn); + + g_mutex_lock(&global_state_lock); + + /* Time only moves forward. Another vcpu might have updated it already. */ + if (new_virtual_time > virtual_time_ns) { + qemu_plugin_update_ns(time_handle, new_virtual_time); + virtual_time_ns = new_virtual_time; + } + + g_mutex_unlock(&global_state_lock); +} + +static void vcpu_init(qemu_plugin_id_t id, unsigned int cpu_index) +{ + vCPUTime *vcpu = qemu_plugin_scoreboard_find(vcpus, cpu_index); + vcpu->total_insn = 0; + vcpu->quantum_insn = 0; + vcpu->last_quantum_time = now_ns(); +} + +static void vcpu_exit(qemu_plugin_id_t id, unsigned int cpu_index) +{ + vCPUTime *vcpu = qemu_plugin_scoreboard_find(vcpus, cpu_index); + update_system_time(vcpu); +} + +static void every_quantum_insn(unsigned int cpu_index, void *udata) +{ + vCPUTime *vcpu = qemu_plugin_scoreboard_find(vcpus, cpu_index); + g_assert(vcpu->quantum_insn >= max_insn_per_quantum); + update_system_time(vcpu); +} + +static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb) +{ + size_t n_insns = qemu_plugin_tb_n_insns(tb); + qemu_plugin_u64 quantum_insn = + qemu_plugin_scoreboard_u64_in_struct(vcpus, vCPUTime, quantum_insn); + /* count (and eventually trap) once per tb */ + qemu_plugin_register_vcpu_tb_exec_inline_per_vcpu( + tb, QEMU_PLUGIN_INLINE_ADD_U64, quantum_insn, n_insns); + qemu_plugin_register_vcpu_tb_exec_cond_cb( + tb, every_quantum_insn, + QEMU_PLUGIN_CB_NO_REGS, QEMU_PLUGIN_COND_GE, + quantum_insn, max_insn_per_quantum, NULL); +} + +static void plugin_exit(qemu_plugin_id_t id, void *udata) +{ + qemu_plugin_scoreboard_free(vcpus); +} + +QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id, + const qemu_info_t *info, int argc, + char **argv) +{ + for (int i = 0; i < argc; i++) { + char *opt = argv[i]; + g_auto(GStrv) tokens = g_strsplit(opt, "=", 2); + if (g_strcmp0(tokens[0], "ips") == 0) { + max_insn_per_second = g_ascii_strtoull(tokens[1], NULL, 10); + if (!max_insn_per_second && errno) { + fprintf(stderr, "%s: couldn't parse %s (%s)\n", + __func__, tokens[1], g_strerror(errno)); + return -1; + } + } else { + fprintf(stderr, "option parsing failed: %s\n", opt); + return -1; + } + } + + vcpus = qemu_plugin_scoreboard_new(sizeof(vCPUTime)); + max_insn_per_quantum = max_insn_per_second / NUM_TIME_UPDATE_PER_SEC; + + time_handle = qemu_plugin_request_time_control(); + g_assert(time_handle); + + qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans); + qemu_plugin_register_vcpu_init_cb(id, vcpu_init); + qemu_plugin_register_vcpu_exit_cb(id, vcpu_exit); + qemu_plugin_register_atexit_cb(id, plugin_exit, NULL); + + return 0; +} diff --git a/contrib/plugins/Makefile b/contrib/plugins/Makefile index 0b64d2c1e3..449ead1130 100644 --- a/contrib/plugins/Makefile +++ b/contrib/plugins/Makefile @@ -27,6 +27,7 @@ endif NAMES += hwprofile NAMES += cache NAMES += drcov +NAMES += ips ifeq ($(CONFIG_WIN32),y) SO_SUFFIX := .dll